Difference between revisions of "Talk:Book - Buchanan's Manual of Anatomy including Embryology 11"

From Embryology
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ranches.— (i) Grey rami communicantes, which spring from the  
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 +
two lacteals, they originate in the fom
 +
a loop. The wall of the lacteal vess(
 +
formed by a single layer of endothelial pk
 +
which are connected by processes with
 +
branched cells of the retiform tissue of
 +
adenoid tissue. The vessel is ensheathec
 +
longitudinal plain muscular fibres der;
 +
from the muscularis mucosae, their fi
 +
cells being connected with the basen
 +
membrane of the villus. The villus is
 +
vaded by adenoid tissue—that is to
 +
retiform tissue with its meshes filled a
 +
amoeboid lymph corpuscles. The branc
 +
cells of this retiform tissue are connectec
 +
processes, on the one hand, with the er
 +
thelial plates which compose the wall of
 +
lacteal vessel, and on the other hand ^
 +
the cells of the basement membrane near
 +
surface, and these latter in turn send
 +
processes between the columnar epith
 +
cells of the free surface.
 +
 
 +
The villi play a most important par
 +
absorption, partly through their cop
 +
capillary networks, and partly through t
 +
lacteals. The lacteals serve specially for
 +
absorption of fats, which is probably effected in the following man
 +
the columnar epithelial cells at the free surface take up the sapon)
 +
and emulsified fats, which they transfer to the amoeboid lymph )
 +
 
 +
 
 +
 
 +
Duodenal Glands
 +
 
 +
 
 +
Fig. 500.—Section of the
 +
Duodenum, showing
 +
Duodenal Glands
 +
(highly magnified).
 +
 
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THE ABDOMEN
 +
 
 +
 
 +
867
 +
 
 +
iscles between them. These corpuscles then carry the fats inwards
 +
rough the adenoid tissue into the lacteal vessel.
 +
 
 +
Duodenal glands (Brunner’s glands) are confined to the duodenum,
 +
id are serially continuous with the pyloric glands of the stomach,
 +
ley are very numerous in the commencement of the duodenum,
 +
iere they form a continuous layer of gland tissue extending as low
 +
the entrance of the bile-duct and pancreatic duct. Beyond this
 +
ant they gradually diminish in number, and ultimately disappear
 +
ar the duodeno-jejunal flexure. They belong to the class of race3 se or acmo-tubular glands,, and they differ from the pyloric glands
 +
the stomach in having their tubules more branched and in having
 +
 
 +
 
 +
Villus ____
 +
 
 +
 
 +
Intestinal Gland
 +
 
 +
 
 +
Solitary Nodule
 +
Muscularis Mucosas
 +
 
 +
 
 +
Submucosa
 +
 
 +
 
 +
Circular Muscular Fibres
 +
 
 +
 
 +
>ngitudinal Muscular Fibres
 +
 
 +
Peritoneal Coat __=§§§=
 +
 
 +
 
 +
 
 +
’Mucosa
 +
 
 +
 
 +
Fig. 501. —Vertical Transverse Section of the Small Intestine
 +
 
 +
(highly magnified).
 +
 
 +
 
 +
iger ducts. Otherwise the structure of the two kinds of glands is
 +
nlar. The duodenal glands lie embedded in the submucous coat,
 +
i their long ducts pass through the whole thickness of the mucous
 +
d, upon the surface of which they open between the intestinal glands,
 +
tte of them, however, open into these glands. The glands can easily
 +
displayed by removing the peritoneal and muscular coats of the
 +
^denum and a little of the submucous areolar tissue, when they
 +
^ear as small, round, grey-coloured masses like millet seeds, varying
 +
diameter from T V to inch.
 +
 
 +
the intestinal glands (crypts of Lieberkiihn) are found in large
 +
fibers over the whole of the mucous membrane of the small intestine,
 +
well as that of the large bowel. They belong to the class of simple
 +
 
 +
 
 +
 
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 +
 
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 +
868
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
tubular glands, and are to be regarded as small diverticula of tl
 +
mucous membrane. Each gland takes the form of a simple tub
 +
which is closed and slightly enlarged at its deep extremity, and opei
 +
by its other end on the surface between the villi. The glands a]
 +
present on the circular folds as well as in the intervening parts. The
 +
are placed vertically and close together, and are confined entirely to tf
 +
mucous coat, in which they extend from the free surface to the musci
 +
laris mucosae. In length they vary from ^ to yTq inch. Each glan
 +
is composed of a basement membrane lined with columnar epitheliun
 +
and the lumen is of large size.
 +
 
 +
The solitary nodules are present over the whole extent of the mucoi
 +
membrane of the small intestine. They assume the form of small, whit
 +
round, or oval nodules, which project by their deep ends into the sul
 +
mucous coat, whilst their superficial ends give rise to slight elevatior
 +
of the free surface, where they have the openings of the intestin;
 +
glands placed around them. They are found upon, as well as betweei
 +
the circular folds. In structure each solitary nodule is composed (
 +
adenoid tissue containing large numbers of lymph corpuscles, and pe:
 +
meated by capillary networks. Each nodule is surrounded at its dee
 +
part by a copious plexus of lymphatic vessels, or by lymphatic sinuse
 +
The solitary nodules are simply lymphoid tissue.
 +
 
 +
The aggregated nodules (Peyer’s patches) are peculiar to the sma
 +
intestine, and average about thirty in number in the adult, bein
 +
 
 +
more numerous in early life. They are situate
 +
along the free or anti-mesenteric border of th
 +
bowel, which must therefore be opened alon
 +
its attached or mesenteric border in order t
 +
preserve them. They are largest, best market
 +
and most plentiful in the lower half of the ileun
 +
In the upper part of the ileum and lower pai
 +
of the jejunum they become smaller and mor
 +
scarce, and they disappear as a rule above th
 +
centre of the jejunum. They vary in lengt
 +
from inch to 4 inches, their breadth rangin
 +
from J inch to 1 inch. They are for the mos
 +
part oblong, their long axis coinciding with tha
 +
of the bowel. In the upper part of the ileui
 +
and lower part of the jejunum, however, the
 +
are somewhat circular. Each aggregated nodul
 +
is composed of a group of solitary lymphoi
 +
nodules, surrounded by lymphatic plexuses c
 +
lymphatic sinuses. The area of each aggregate
 +
nodule is slightly elevated, and there are no vil
 +
over the lymphoid nodules, whilst the opening
 +
of the intestinal glands are arranged in
 +
 
 +
 
 +
 
 +
Fig. 502.—An Aggregated Lymphoid
 +
Nodule.
 +
 
 +
 
 +
circular manner round each nodule. There are no circular folds ove
 +
the aggregated nodules. The aggregated nodules are best marke
 +
in young persons. Towards middle life they fade away, and in ol
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN 869
 +
 
 +
persons they are usually only distinguishable as discoloured portions
 +
of the mucous membrane.
 +
 
 +
Blood-supply—Arteries.—The duodenum receives its arteries from
 +
the superior pancreatico-duodenal of the gastro-duodenal from the
 +
hepatic, and the inferior pancreatico-duodenal of the superior mesenteric. The jejunum receives its arteries from the jejunal branches of
 +
the superior mesenteric. The ileum receives its arteries from the ileal
 +
arteries, and its terminal part in addition receives its arterial supply
 +
from the ileal branch of the ileo-colic from the superior mesenteric.
 +
 
 +
Veins.—The destination of the venous blood of the small intestine
 +
is the superior mesenteric vein, and thereafter the portal vein. The
 +
veins are provided with valves which are competent in early life,
 +
but in the adult they are incompetent, and therefore allow regurgitation of blood to take place towards the small intestine, as happens
 +
in cases of portal obstruction.
 +
 
 +
Lymphatics.—These form a copious plexus of valved vessels, which
 +
is situated in the submucous coat. This plexus receives the lymphatics of the mucous membrane and the lacteals of the villi, and it
 +
surrounds the deep ends of the solitary nodules. Its efferent vessels
 +
pierce the muscular coat, and in doing so they take up the lymph
 +
from an intramuscular plexus of lymphatics, which lies between the
 +
longitudinal and circular layers. They then leave the bowel at the
 +
mesenteric border, where they pass between the two layers of the
 +
mesentery, and on their way to the cisterna chyli they traverse the
 +
superior mesenteric glands.
 +
 
 +
Nerves.—These are derived from the superior mesenteric sympathetic plexus, and they form two gangliated plexuses of nonmedullated nerve-fibres. One of these is situated in the muscular
 +
coat between the longitudinal and circular layers, and is known as
 +
the myenteric plexus (Auerbach’s plexus) (plexus of the muscular coat of
 +
the intestine). The other is situated in the submucous coat, and is
 +
called the plexus of the submucosa (Meissner’s plexus). The branches
 +
of this latter plexus are distributed to the muscularis mucosae and the
 +
mucous membrane with its villi.
 +
 
 +
Characters of Different Parts of the Small Intestine—Duodenum — Peritoneum. —There is no mesentery and only a partial investment of peritoneum.
 +
Muscular coat. —This is very thick. Submucous Coat.- —-This contains the tubular
 +
portions of the duodenal glands. Mucous Coat .—The characters of this coat
 +
are as follows: (1) circular folds, except in the first 1 or 2 inches, (2) villi, (3) intestinal glands, (4) solitary nodules, (5) ducts of the duodenal glands, (6) common
 +
orifice of the bile-duct and pancreatic duct, and (7) orifice of the accessory pancreatic duct.
 +
 
 +
The diameter of the duodenum is from 1^ to 2 inches.
 +
 
 +
Jejunum — Peritoneum. —There is a mesentery, and the bowel is surrounded by
 +
peritoneum except along its mesenteric border. Muscular Coat .—This is comparatively thin. Mucous Coat .—This has the following characters: (1) circular
 +
folds, (2) villi in abundance, (3) intestinal glands, (4) solitary nodules, and
 +
(5) aggregated lymphoid nodules in its lower half.
 +
 
 +
The diameter of the jejunum is about i-| inches.
 +
 
 +
Ileum — Peritoneum. —In this respect the ileum resembles the jejunum.
 +
 
 +
 
 +
870
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Muscular Coat. —This is very thin. Mucous Coat. —The characters of this co,
 +
are as follows: (1) circular folds in upper half, but small and sparse, there beii
 +
none in the lower half; (2) villi, but in fewer numbers; (3) intestinal gland
 +
(4) solitary nodules; and (5) aggregated lymphoid nodules.
 +
 
 +
The diameter of the ileum is about 1^ inches.
 +
 
 +
Development of Small Intestine. —The epithelial lining is at first like th
 +
 
 +
of the stomach, and the muscular coat develops also in a similar way. Vacuol
 +
appear in the epithelium, leading in the duodenum to subdivision of the lume
 +
but not in the rest of the gut, where, however, they may produce pouches. Vi
 +
appear in the upper part first, about the seventh week, and are found throughoi
 +
the gut in the fourth month. They may form by the breaking up of longitudin
 +
ridges, or may form separately. Glands develop as simple pits between villi
 +
the fourth month, first in the upper gut. They tend to branch later. T,
 +
duodenal glands seem to be formed from the simple forms by lateral branchii
 +
and growth in length during the fourth month. They are not fully formed ;
 +
birth, however.
 +
 
 +
Large Intestine.—The wall of the large intestine, which is sacculate*
 +
is composed of four coats—serous, muscular, submucous, and mucou
 +
 
 +
The serous coat forms a complete investment to the vermifori
 +
appendix, caecum, transverse colon, and pelvic colon. As regarc
 +
the ascending colon and descending colon, it is incomplete, being absei
 +
behind.
 +
 
 +
The muscular coat (muscularis externa) is composed of plain muscuk
 +
tissue disposed in two layers—external or longitudinal, and internal (
 +
circular.
 +
 
 +
The longitudinal muscular fibres are for the most part collected ini
 +
three flat bands, called taeniae coli, except upon the rectum. In tl
 +
intervals between these bands there are some longitudinal fibres, but the
 +
are very few and scattered. The taeniae, which are about J inch i
 +
breadth, commence upon the caecum at the base of the vermiform a]
 +
pendix, and they extend along the several parts of the large intestir
 +
as far as the rectum, where they spread out and form a continuot
 +
covering, which completely surrounds that part of the bowel. Upc
 +
the caecum, ascending colon, descending colon, and iliac colon the teni
 +
from their disposition are called anterior, postero-internal, and poster*
 +
external. Upon the transverse colon they are so placed as to be calle
 +
anterior or omental (greater omentum), postero-inferior or free, an
 +
superior or meso-colic (transverse meso-colon). They are shorter tha
 +
the bowel to which they are applied, with the result that the tube
 +
drawn together or puckered, and thus thrown into sacculi. Thei
 +
being three taeniae, there are three rows of sacculi between them, an
 +
inasmuch as the taeniae are placed at nearly equal distances from eac
 +
other, the sacculi are pretty much of equal dimensions. Between th
 +
successive sacculi there are constrictions, usually containing fat. Th
 +
sacculi give rise internally to large pouches, and the constrictior
 +
between the sacculi produce internally sharp crescentic rugae, whic
 +
separate the pouches from each other. When the taeniae are divide*:
 +
the sacculi and constrictions entirely disappear, and the large bow*
 +
becomes elongated into a smooth cylindrical tube. Along the cours
 +
of the taeniae there are a number of small processes of peritoneum cor
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
871
 +
 
 +
 
 +
ining fat, called appendices epiploicae. They are best marked on the
 +
ansverse colon and on the upper part of the pelvic colon, and are least
 +
arked, as a rule, on the caecum. Except in the case of the transverse
 +
)lon, these are chiefly found along the postero-internal taenia, but in
 +
le case of the transverse colon they are principally met with along the
 +
Dstero-inferior taenia.
 +
 
 +
The circular fibres are thin and scattered over the sacculi, but in
 +
le constrictions between them they become aggregated. Upon the
 +
ctum and anal canal they form a thick layer, which in the latter
 +
tuation is known as the sphincter ani internus.
 +
 
 +
The submucous coat is in all respects similar to that of the small
 +
Ltestine.
 +
 
 +
The mucous coat is pale and greyish in colour, except in the rectum,
 +
here it is red. Its epithelium is similar to that of the small intestine.
 +
 
 +
; is destitute of circular folds and villi, and consequently presents a
 +
nooth surface. It contains large numbers of intestinal glands, which
 +
iound in mucus-secreting goblet cells. It also contains solitary
 +
anphoid nodules, which are especially prevalent in the vermiform
 +
ppendix and caecum. The deepest part of the mucous coat is formed
 +
y the musculans mucosce ( muscularis interna).
 +
 
 +
Blood-supply—Arteries.—These are as follows: (1) appendicular,
 +
>r the vermiform appendix; (2) anterior and posterior caecal, for the
 +
mim; (3) colic of ileo-colic and right colic, for the ascending colon;
 +
|.) middle colic, for the transverse colon (all branches of the superior
 +
lesenteric); (5) left colic, for the descending colon; and (6) sigmoid
 +
rteries, for the iliac colon and pelvic colon (the latter two being branches
 +
f the inferior mesenteric).
 +
 
 +
Veins.—The destination of the venous blood of the vermiform
 +
ppendix, caecum, ascending colon, and transverse colon is the superior
 +
lesenteric vein, whilst the blood of the descending colon, iliac colon,
 +
nd pelvic colon is carried into the inferior mesenteric vein. In both
 +
ases the further destination of the blood is the vena portae. As in the
 +
mall intestine, the veins have valves which are competent in early life,
 +
ut not so in the adult.
 +
 
 +
The lymphatics will be found described on pp. 799 and 802.
 +
 
 +
Nerves.—These are derived from the superior mesenteric sympathetic plexus and the inferior mesenteric plexus, which latter is an
 +
ffshoot from the aortic plexus. The disposition of the nerves correponds with that in the small intestine.
 +
 
 +
The large intestine diminishes gradually in size from its commencement to its termination. Its diameter varies in different parts, the
 +
xtremes being 2\ inches and 1 inch.
 +
 
 +
Characters of the Large Intestine — Peritoneal Coat. —This presents at frequent
 +
ntervals small projections called appendices epiploicae. Muscular Coat. —The
 +
ongitudinal fibres are for the most part arranged in three taeniae. Mucous
 +
"oat. —This is destitute of ( a ) circular folds, (b) villi, (c) duodenal glands, and
 +
d ) aggregated nodules, but it is provided with (1) intestinal glands, and (2) solitary
 +
lodules. Outline of Tube. —The bowel presents three rows of sacculi, except in
 +
-he vermiform appendix and rectum.
 +
 
 +
 
 +
 
 +
872
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Development. —There is nothing remarkable about the epithelial grow
 +
which resembles that of the small gut. The lumen is at first very small and
 +
walls thick. The bowel begins to enlarge about the time of its entrance ii
 +
the belly, but even then is much smaller than the small intestine. Villi deve'
 +
in it during the fourth month, but become smaller and less distinct during
 +
succeeding months. Glands form between the villi, but the details of their forr
 +
tion are not known with certainty. Villi are found in the vermiform appea
 +
in the fourth month, with gland formation.
 +
 
 +
 
 +
Structure of the Vermiform Appendix.—The vermiform appenc
 +
is entirely covered by peritoneum, which forms a more or less compk
 +
 
 +
 
 +
 
 +
Solitary Nodules
 +
 
 +
 
 +
Fig. 503.—Transverse Section of the Vermiform Appendix
 +
 
 +
(magnified).
 +
 
 +
meso-appendix or appendicular mesentery. It has a muscular coa
 +
composed of an external longitudinal and internal circular layer, both <
 +
which completely surround it. The submucous coat contains in gre;
 +
abundance solitary nodules of large size, and the mucous coat contaii
 +
a few solitary nodules, as well as a few intestinal glands. The base <
 +
the appendix is situated at a point on an average rather more tha
 +
1 inch below the ileo-colic valve, according to Treves. The openir
 +
by which the appendix communicates with the caecum is occasional
 +
guarded by a fold of mucous membrane, which is known as the ileo-coll
 +
valve (valve of Gerlach).
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
873
 +
 
 +
The vermiform appendix is usually regarded as the remains of the herbivorous
 +
aecum. It is also looked upon as an appendage of the lymphoid system, and as
 +
ich it would belong to the class of structures represented by aggregated nodules
 +
-namely, lymphoid organs.
 +
 
 +
Ileo-colic Valve (Valve of Tulpius).—This valve is situated at the
 +
oint where the terminal part of the ileum opens into the junction
 +
etween the caecum and ascending colon. The orifice, as seen from the
 +
iterior of the large intestine, has the form of a slightly oblique cleft
 +
bout J inch long, and running in an antero-posterior direction. It is
 +
ounded above and below by the two segments which form the valve,
 +
nd which project into the large intestine. The upper or ileo-colic
 +
egment is prominent, and occupies an almost horizontal plane. The
 +
 
 +
 
 +
 
 +
Dwer or ileo-ccecal segment, longer than the upper, is concave superiorly,
 +
nd occupies an oblique plane. The anterior part of the cleft is rounded
 +
h, whilst the posterior part tapers to a point. The segments meet in
 +
ront of and behind the cleft, and form two prominent folds, which are
 +
>rolonged round the wall of the bowel for some distance. These folds
 +
re known as the frenula. Each segment is composed of two layers
 +
»f mucous membrane, one of which belongs to the ileum, and the other
 +
0 the caecum or colon, as the case may be. These two layers are coninuous with each other at the free margin of the segment, and they
 +
ontain between them submucous areolar tissue and circular muscular
 +
Tres, both of which are derived partly from the ileum and partly from
 +
he large intestine. The longitudinal muscular fibres and the serous or
 +
>eritoneal coat take no part in the formation of the segments, being
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
874
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
continued uninterruptedly from the ileum to the large intestine. '
 +
mucous membrane which covers the opposed surfaces of the segrm
 +
belongs to the ileum, and is therefore provided with villi. The muc
 +
membrane of the other surfaces—that is to say, the surfaces which I
 +
away from each other (downwards and upwards respectively)—be!
 +
to the caecum and colon, and are destitute of villi. The villi thus <
 +
appear at the margins of the segments. The valve may be descril
 +
as being formed by an inversion of the terminal part of the ileum i
 +
the large intestine. That part of the ileum, having passed upwa
 +
and to the right with a slight inclination backwards, enters the la
 +
intestine. As it does so it leaves behind its serous and longitudi
 +
muscular coats, and takes with it its circular muscular, submucc
 +
and mucous coats, the corresponding coats of the large intest
 +
accompanying it in the inversion. The ileo-colic valve prevents
 +
regurgitation of the contents of the caecum into the ileum. It
 +
generally believed that the mode of action of the valve is as folio 1
 +
when the caecum becomes distended the frenula of the valve are stretcl
 +
and exercise traction upon its segments, which are thereby brou|
 +
together. The valve is usually represented in figures as it appears wl
 +
the caecum has been inflated and dried. In the fresh condition
 +
segments of the valve are thick and tumid, and the appearance is ]
 +
unlike that of the pyloric valve as seen from the duodenum or of
 +
cervix uteri as seen from the vagina; the frenula, again, are much 1
 +
apparent in such a caecum.
 +
 
 +
For the structure of the rectum, see p. 960.
 +
 
 +
Development of Positions of the Stomach and Intestinal Canal.
 +
 
 +
This subject is dealt with shortly on pp. 61-65 and 79-81. These pa
 +
should be studied before reading what follows.
 +
 
 +
Dorsally, the roof of the mid-gut is at first close to the notochord, but,
 +
growth goes on, it comes away from this close relationship, drawing out
 +
mesoderm between them as it does so, to form the dorsal mesentery, the man
 +
in which this change is effected is not quite clear.
 +
 
 +
At an early stage, therefore, the alimentary tube in the abdomen can
 +
described as being short, median in position, extending from the septum tra
 +
versum to the cloaca, and, between these limits, making a short curve, com
 +
ventrally, and suspended by a median dorsal mesentery. The vitelline duct
 +
attached to it at the lowest part of its curve, and as development proceeds 1
 +
intestinal loop lengthens, so that this lowest part of it passes out of the abdon
 +
into the ‘ umbilical sac.’ The elongation of the loop implies a correspond!
 +
lengthening of the dorsal mesentery opposite it (see Fig. 44).
 +
 
 +
Stomach. —This is a dilatation of that part of the tube which is resting
 +
the septum transversum. Its attachment here lengthens and thins as the li 1
 +
grows in the septum, and at the same time its dorsal mesentery (meso-gastriu
 +
is pouched out to the left, carrying the stomach with it, and turning it so tl
 +
its left surface becomes somewhat ventral. The pouch of dorsal meso-gastrii
 +
is known as the omental bursa.
 +
 
 +
Intestinal Canal. —This canal is at first very short and almost straight, aij
 +
gs has been stated, it communicates freely with the yolk-sac. At this sh
 +
there is no indication of a division into small and large intestine. When
 +
wide opening leading to the yolk-sac becomes constricted and converted i:
 +
the vitelline duct, the intestinal canal undergoes lengthening, and a conspicu'
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
8 75
 +
 
 +
 
 +
) is formed, which projects into the cavity of the proximal part of the umbilical
 +
i, this cavity being a direct prolongation of the coelom or body-cavity. This
 +
) is spoken of as the U-loop. The convexity of the bend of the loop is directed
 +
! ralwards, and the vitelline duct is connected with the convexity. The loop
 +
two limbs, which lie at first parallel to each other. One limb is cephalic,
 +
>er, or proximal, and leads from the duodenal loop of the gut; the other limb
 +
audal, lower, or distal, and leads to the caudal end of the gut. Upon the
 +
al limb a bud makes its appearance. This assumes the form of a blind diverlum, or cul-de-sac, which is the rudiment of the ceecum. The appearance of
 +
caecal evagination is the first indication of the division of the intestinal canal
 +
> small and large intestine. The primitive small intestine is the part on the
 +
 
 +
 
 +
 
 +
 
 +
Fig. 5 ° 5 - —The U-Loop, 8 mm., just projecting into the Umbilical Sac.
 +
Left and right views. Vitelline duct cut Short.
 +
 
 +
 
 +
)ximal side of the rudimentary cascum, and the primitive large intestine is the
 +
ft extending from the rudimentary caecum to the caudal end of the gut.
 +
 
 +
The portion of mesentery which is drawn out as the proper mesentery of the
 +
loop contains the superior mesenteric artery between its layers. The artery
 +
originally continued on beyond the loop as the vitelline artery, but this soon
 +
appears and leaves its trunk as the superior mesenteric.
 +
 
 +
As the stomach lies in the front wall of the rudimentary lesser sac (bursa
 +
lentalis), its pyloric end is directed towards the right, and the very short piece
 +
the tube which comes next, the future duodenum, lies rather to the right of the
 +
ddle line, and is attached to the median common dorsal mesentery by a thick
 +
so-duodenum, which projects on that side of it, just below the opening of the
 +
ser sac.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
8y6
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
The intestinal tract is thus seen to consist of intra- and extra-abdorr
 +
portions, part of the colon being in the abdomen, and the anterior limb of
 +
loop being connected with the duodenum by an intra-abdominal duod
 +
umbilical loop of gut.
 +
 
 +
These different parts of the intestinal tract can be seen in Fig. 505, in w
 +
the conditions in a 8 mm. embryo simplified are shown from both sides; the
 +
lobe of the liver has been cut away to expose the mesentery and gut, for it cc
 +
down at this stage on the left side of the bursa omentalis and mesentery a:
 +
as the right lobe on the other side. The neck of the umbilical loop of gut p<
 +
out between the two lobes of the liver in a deep notch in the ventral edge oJ
 +
 
 +
 
 +
 
 +
Fig. 506.—Left-sided Views of Umbilical Loop at 9 mm. (Above) and 10 1
 +
 
 +
(Lower Figure).
 +
 
 +
organ. An angled bend is seen where the hind-gut is continuous with the hin
 +
limb of the loop; this is produced by the attachment here to the gut of a retent
 +
band in the mesentery, extending from the peri-aortic region in the neighbourhc
 +
of the cceliac artery. The angle must not be mistaken for the left colic flexu
 +
with which it has nothing to do; it is gradually effaced as development procee
 +
and its ultimate position, if it persisted, would be some little distance to 1
 +
left of the mid-point of the transverse colon.
 +
 
 +
With the exception of the short length of the duodeno-umbilical piece, wh
 +
becomes the first coil of the jejunum, the small intestine is formed in the umbili
 +
sac, as are those parts of the large gut which become the ascending and right k
 +
of the transverse colon. Formed in this sac, the gut enters the abdomen a
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
877
 +
 
 +
 
 +
ain stage, and within this cavity is finally disposed in its proper situations.
 +
 
 +
: processes that lead to the ‘ rotation ’ of the intestine can thus be divided
 +
descriptive purposes into three stages—the development outside the belly,
 +
entrance into the abdomen and the immediate mechanical results of this
 +
nge, and the subsequent assumption of the definitive positions.
 +
 
 +
 
 +
 
 +
Fig. 507.—Two Diagrams to show Earlier Stages of Gut and
 +
Mesentery within the Belly and in the Umbilical Sac.
 +
 
 +
 
 +
First Stage. —The general disposition in the earlier part of this stage can be
 +
a in Fig. 507, A and B. It is marked by the fairly rapid growth in length of
 +
anterior or proximal limb of the umbilical loop, forming coils. The ruditttary lesser sac enlarges, passing down on the left side of the median abdominal
 +
sentery, between it and the liver. Two or three points in connection with the
 +
 
 +
 
 +
 
 +
1. 508.—Schemes of the Umbilical Loop showing the Sort of Growthchanges THAT OCCUR WITHIN IT (SEE TEXT).
 +
 
 +
ngating proximal limb must be noted, as they are concerned with the subseent entry and disposal of the gut within the belly cavity: in the first place,
 +
' proximal limb lies, from an early stage on the right side * of the loop, as can
 +
 
 +
 
 +
* The immediate cause of this is not certain. It may be due to the position
 +
the stomach, making the duodenum pass towards the right, or it may be
 +
iociated with the development of the vitello-umbilical anastomosis, which
 +
3 in the concavity of this part of the limb of the loop, but any definite state"nt on the subject would be unwarranted.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
878
 +
 
 +
be seen in the figures; secondly, the growth of the proximal limb is associated w
 +
marked increase in the depth of the corresponding mesentery of the loop,
 +
that the distance between the coils of this limb and the superior mesente
 +
artery is much increased; the hinder limb of the loop does not grow like 1
 +
proximal limb, and its distance from the artery remains unchanged, whence
 +
comes about that the artery gets relatively nearer and nearer to the hinder lii
 +
of the loop. At the back of the loop, where it is passing through the open:
 +
in the abdominal wall, the artery is still approximately midway between the t
 +
limbs, and it is only distal to this that the unequal growth of the constituent pa
 +
of the mesentery of the loop leads to the one-sided position of the vessel.
 +
 
 +
Fig. 509 illustrates the appearance at the end of the first stage. The cseci
 +
is now a large dilatation with a conical extremity, placed on the left side of •
 +
mass of coils of small intestine. The mesentery of the small gut is long, and 1
 +
superior mesenteric artery is close to the colon and caecum. The bursa omenh
 +
really extends caudally along the whole extent of the left side of the int
 +
abdominal colon and meso-colon, separating these from the left lobe of the liv
 +
in the figure, however, it is shown as somewhat pushed up, to allow the med:
 +
colon and meso-colon to be seen. At the end of this stage, then, the intesti:
 +
coils are on the right of the caecum and colon in the umbilical sac, the super
 +
mesenteric artery is close to the colon and far from the coils, and the bu
 +
omentalis is on the left of a ‘ median abdominal septum ’ made of abdominal coi
 +
and meso-colon.
 +
 
 +
Second Stage. —The recession of the umbilical gut within the belly is brou^
 +
about by a fall in ‘ intra-abdominal tension ' resulting from lessened growth-r
 +
of the liver. This organ fills all the available space in the abdomen during 1
 +
second month, growing pari passu with the surrounding parts, but in the ea
 +
part of the third month its rate of growth falls behind that of these parts. T
 +
does not at first affect the mass in the umbilical sac, and is met by increase in 1
 +
amount of blood in the liver vessels, which are consequently dilated. In 1
 +
tenth week, however, approaching the 40 mm. stage, this dilatation of lr
 +
vessels may be considered to have reached its maximum, and any further incre;
 +
in the capacity of the abdomen calls for the appearance of some additional si
 +
stance to fill the space which otherwise must come into being. The umbili
 +
coils are alone able to fulfil this role, and the extra-abdominal or amniotic pressi
 +
not being lessened by the fall in the growth-rate of the liver, the contents of 1
 +
umbilical sac are pushed by it into the abdomen to compensate for the inter:
 +
fall. It is to be noted now that as the coils enter the abdomen the liver can retr;
 +
before them by the discharge of blood from its over-dilated vessels. Thus 1
 +
distension of the liver not only leads to the beginning of the intestinal mo
 +
ment, but, by its disappearance and the tendency of the organ to return to
 +
undistended condition, leads to the completion of the recession and the provis:
 +
of space for the entering coils when and where it is needed, without any pressi
 +
on these coils.
 +
 
 +
The movement having started, all the evidence points to it being rapi(
 +
completed. Owing to the size of the caecum, possibly also owing to the gr<
 +
size of the dilated venous spaces found round it at this stage, and to the srr
 +
size and thick wall of the colon, the ccecum is retained in the sac to the last, a
 +
the proximal limb passes first into the abdomen. It does this, not en masse, 1
 +
in continuity, slipping into the belly with its mesentery, the elongation of wh
 +
allows it to enter the abdomen, although the superior mesenteric vessels a
 +
the colic part of the distal limb are still in the sac. But the proximal limb
 +
already been seen to be on the right-hand side of the distal limb, so that it ent
 +
the abdomen below the right lobe of the liver, which retreats before it—that
 +
the coils of intestine enter the belly on the right-hand side of the median colic ‘ septu
 +
(Fig. 509) already mentioned. This ‘ septum ' of abdominal colon and mecolon is thus pushed over to the left by the coils, as seen in Fig. 510, and 1
 +
back against the left dorsal wall of the abdomen, the coils lying on its vent
 +
(originally right) surface. Crossing in this way to the left, the coils necessak
 +
pass below the colic part of the distal limb of the loop and the mesenteric artery, wb*
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
879
 +
 
 +
 
 +
 
 +
509
 +
 
 +
 
 +
■The Condition within the
 +
Gut enters the Abdomen:
 +
 
 +
 
 +
Umbilical Sac shortly before the
 +
Left and Right Views.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
88 o
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
 
 +
is, as already seen, associated with this limb. Moreover, in going to the le
 +
and in pushing the median septum to this side, the coils have passed on tl
 +
dorsal side of the lower part of the omental bursa, which now hangs down ov
 +
them; this is the first form of the greater omentum of the definitive state, althou^
 +
there is as yet no adhesion between the overhanging layers and the colon, (
 +
between it and the dorsal wall.
 +
 
 +
The ccecum is the last structure to enter the abdomen, and, on entering, it li
 +
(Fig. 512) on the mass of coils of small intestine. It forms an angle, howeve
 +
with the rest of the colon when it lies in this situation, and as the colon is thic'
 +
walled, there is a tendency for the bent piece to straighten itself and come in
 +
line with the rest; this, and doubtless also the rapid increase in size of the coils
 +
the small gut, which now begins, cause the caecum to assume a right dors
 +
 
 +
 
 +
Fig. 510.—Diagram of Section through Root of the Loop, showing ho
 +
its Cranial Limb, being below and on the Right of the Other, mu:
 +
 
 +
PASS BELOW THE CAUDAL LlMB AND THE MAIN VESSELS AND PUSH TP
 +
 
 +
Intra-abdominal Meso-colon to the Left.
 +
 
 +
Overhanging omental bursa is represented as rolled up.
 +
 
 +
position with reference to the mass of coils, on the right side of the neck of tl
 +
mass, and thus to come into its proper plane. This is found to occur a few da;
 +
after the entrance of the gut into the belly, and with its occurrence the secor
 +
stage comes to an end.
 +
 
 +
Third Stage. —It can be understood from a consideration of the figures that tl
 +
caecum and end of the colon, when they move to the right, must pass over ti
 +
line of the superior mesenteric artery, for the mesentery of the small intestn
 +
is attached along the line of the artery on its lower aspect. Thus the cole
 +
will come to lie across the duodenum, and the caecum below and to the rig!
 +
of this, and the artery will cross the duodenum lower down. This complet
 +
the twist of the mesentery of the loop, which finishes the second stage, ar
 +
leaves the peritoneal layers now in a position which can be understood from tl
 +
scheme in Fig. 463.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
881
 +
 
 +
 
 +
The intestines are now essentially in their proper ‘planes/ and the third
 +
t e comprises only the developments and extensions in these positions that
 +
l to the conditions found m the adult. The descending meso-colon, laid
 +
 
 +
 
 +
 
 +
. 511.— Scheme to show Result
 +
>f Entry of Proximal Limb to
 +
rHE Right of Median Septum,
 +
 
 +
VHICH IT PUSHES TO THE LEFT
 +
>lND Dorsally against the
 +
Dorsal Wall: Cecum remains
 +
n the Sac.
 +
 
 +
 
 +
 
 +
Fig. 512.—Conditions immediately
 +
 
 +
AFTER THE ENTRANCE IS ACCOMPLISHED.
 +
 
 +
The caecum and mesenteric vessels lie
 +
on the mass of coils, the vessels to
 +
the right.
 +
 
 +
 
 +
k against the left dorsal wall, as seen in Fig. 463, is, at the beginning of this
 +
*e, relatively short, so that the left colon only reaches the inner edge of the
 +
it aspect of the left kidney; as growth proceeds, this meso-colon lengthens,
 +
 
 +
 
 +
 
 +
5 r 3 -—Actual Conditions in Embryo just after Cecum has entered the
 +
Belly at the End of Second Stage.
 +
 
 +
 
 +
1 the colon thus comes to lie farther out, finally reaching its definitive position,
 +
1 the meso-colon becomes adherent to the dorsal wall. This dorsal adhesion
 +
presses from within outwards, and when the colon has reached its final posi
 +
56
 +
 
 +
 
 +
 
 +
 
 +
 
 +
882
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
tion, extends to the line of the gut, and thus fixes the bowel in situ. Or
 +
right side the colon, about the end of the third month, becomes attached v
 +
it crosses the duodenum, and at its caecal end. Between these two fixed
 +
the colon and meso-colon are free at first, but attachment of the meson
 +
just to the right of the superior mesenteric vessels is soon found. The l
 +
between the fixed parts slowly lengthens as the liver gets relatively sm
 +
and as it lengthens it becomes curved out with a convexity upwards and t
 +
right, ultimately forming in this way the hepatic flexure with the ascei
 +
and right portion of the tranvserse colon. The formation of these parts
 +
slow process, not really completed at birth. It is accompanied by an extei
 +
of the area of meso-colic adhesion, this, however, falling short of the lii
 +
advancing colon, so that this is free to lengthen farther. Thus the mesopart of the original loop mesentery becomes attached to the dorsal wall, the
 +
 
 +
 
 +
 
 +
Fig. 514.— Schemes to show Position of Meso-colon and Colon at Var
 +
 
 +
Stages, indicated by the Measurements.
 +
 
 +
a, b, left and right mesocolons; t, position at birth.
 +
 
 +
remaining free as the mesentery of descriptive anatomy; the line of attack
 +
of the mesentery is therefore in reality the limit of adhesion of the right meso-cc
 +
Between the upper end of the fixed meso-colon on the left and the att
 +
ment to the duodenum on the right the free colon and meso-colon are apj
 +
to the dorsal aspct of the lower part of the rudimentary lesser sac, invagina
 +
this somewhat. The colon stands away from the dorsal wall here, and it is
 +
dorsal surface of the meso-colon, the surface continuous with the adhe
 +
surfaces of the right and left meso-colons, that is applied (see Fig. 463) to
 +
wall of lesser sac. The adhesion of these applied parts to each other, extendir
 +
far as the position of the pancreas in the wall of lesser sac, brings into existence
 +
transverse meso-colon and the incidental attachment of the greater omentum tc
 +
transverse colon', by extension of the adherent area the bursal wall above
 +
pancreatic line becomes fixed to the dorsal wall, and constitutes the posU
 +
wall of the small sac.
 +
 
 +
Caecum and Vermiform Appendix. —The caecum appears about the
 +
week of embryonic life as a bud in connection with the distal limb of the U
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
883
 +
 
 +
 
 +
intestine. It assumes the form of a blind diverticulum, which is at first of
 +
liform dimensions. It soon, however, becomes conical. The proximal part
 +
idergoes enlargement, and represents the permanent caecum. The distal part
 +
mains long and narrow, and represents the vermiform appendix, which ultimately
 +
jcomes connected with the left and posterior part of the caecum. The various
 +
)sitions occupied by the caecum and its migration to the right iliac fossa have
 +
st been referred to. Suffice it to say that it lies at first on the left side of the
 +
edian line, then it crosses to the right side, being at this stage below the liver,
 +
id finally is left in position as the liver retracts.
 +
 
 +
 
 +
Peritoneal Structures.
 +
 
 +
1. Meso-gastrium. —It has been pointed out that the part of the dorsal
 +
minion mesentery which carries the stomach becomes pouched out to the left ;
 +
ie resulting sac is frequently termed the meso-gastrium, but more appropriately
 +
le rudimentary lesser sac (bursa omentalis). Its opening, to the right, is just
 +
x>ve the thick part of the mesentery known as the meso-duodenum, and is
 +
datively small. The sac is the result of rapid increase of a right-sided depression
 +
: the mesentery, the pneumato-enteric recess ; a left-sided recess shows itself
 +
sry early, but disappears almost at once. The opening corresponds in the
 +
iult with the line of the pancreatico-gastric folds. The portion of the lesser sac
 +
etween these and the opening into lesser sac is added later as an additional
 +
;cess to the right of the mesenteric line, associated with the growth of the
 +
iferior vena cava.
 +
 
 +
The rudimentary lesser sac is at first ‘ free ’ towards the left. After the return
 +
E the bowel, which (see Fig. 511) has caused the colon to invaginate its lower
 +
rail, the dorsal wall of the sac becomes attached to the abdominal wall, while the
 +
olon becomes fixed to its lower aspect. Thus the left half of the transverse
 +
leso-colon comes into existence, attached dorsally, while the pancreas, which
 +
ad extended in the back layers of the sac, now becomes fixed dorsally, the
 +
tyers behind it disappearing. The spleen forms in the outer part of the sac
 +
all, which, as the result of the fixation just described, has now a dorsal attachlent towards the left.
 +
 
 +
The outer part of the sac wall, thus left still ' free,’ is therefore the structure
 +
;rmed the ‘ meso-gastrium’ in the adult; the spleen, placed in this, is held by
 +
to the dorsal wall on the one hand (lieno-renal fold) and, on the other, to the
 +
:omach (gastro-splenic ligament).
 +
 
 +
The greater omentum is evidently made by the bulging of the front and lower
 +
art of the rudimentary sac over the colon, to which it acquires a secondary
 +
ttachment. The lesser omentum (ventral mesentery) is drawn out from the
 +
upturn transversum.
 +
 
 +
2. The meso-duodenum is a thickening of the median mesentery just below the
 +
pening into the lesser sac. The duodenum is attached on its right front, and
 +
1 at first a very short segment of the tube. The two pancreatic outgrowths
 +
ccur into the meso-duodenum, the upper one being immediately below the
 +
pening into lesser sac and opposite the attachment of its lower and back wall,
 +
ito which it extends. The lower growth, forming the head of the gland, enlarges
 +
1 the meso-duodenum, with corresponding lengthening of the duodenum, which
 +
Iso begins to assume a curved form round the growing head. The whole curve
 +
f the duodenum is ultimately formed in this way as a result of the growth of the
 +
ead of the pancreas. It is clear, then, that this curve has nothing to do with
 +
tie rotation of the gut returning to the abdomen, but it is possible that the
 +
xtreme end of the duodenum may belong to the commencement of the proximal
 +
nib of the loop, secondarily fixed in position.
 +
 
 +
3 - Caecum. —The caecum, being originally a bud or outgrowth of the gut, has
 +
o mesentery, and is originally entirely surrounded by peritoneum.
 +
 
 +
4 - Vermiform Appendix. —The vermiform appendix, being originally the
 +
find narrowed end of the caecum, or, in other words, a diverticulum of the
 +
‘Scum, is also destitute of a mesentery, properly so called, and is invested by
 +
 
 +
 
 +
884
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
an extension of the peritoneal envelope of the caecum. There is, however,
 +
most cases a fold of peritoneum pertaining to the vermiform appendix, whi
 +
extends along it for about one-half or two-thirds of its length. This fold
 +
called the meso-appendix or appendicular mesentery, and it is derived from t
 +
left or inferior layer of the mesentery proper, close to the ileo-colic junctic
 +
Its presence is due to the drawing out of vessels as the appendix is formed.
 +
 
 +
 
 +
Structure of the Liver.
 +
 
 +
 
 +
The liver has two coats, external and internal. The external
 +
serous coat is formed by the peritoneum, and is incomplete (see p. 77*
 +
Within the serous coat is the fibrous or areolar coat, which is kno\
 +
as the fibrous capsule of the organ. It is for the most part thin, exce
 +
where the peritoneal coat is deficient. It is continuous all over t
 +
surface with the scanty amount of areolar tissue which pervades t
 +
interior of the organ and connects the hepatic lobules. At the por
 +
hepatis it surrounds the common hepatic duct, hepatic artery, ai
 +
vena portae, under the name of the capsule ofiGlisson. The subdivisio
 +
of this capsule accompany the various branches of the duct, arter
 +
and vein as these ramify throughout the liver in the portal cana'
 +
 
 +
The liver substance is composed of a gre
 +
number of small polyhedral masses, call
 +
hepatic lobules, which are closely pack<
 +
together, and at the centre of each of whi<
 +
is an intralobular or central vein. In m<
 +
there is very little areolar tissue between t]
 +
lobules, which are therefore for the most pa
 +
confluent. In some animals, however, notab
 +
the pig and camel, there is a very distin
 +
amount of areolar tissue between the lobule
 +
which therefore stand clearly apart from ea(
 +
other.
 +
 
 +
The average diameter of a hepatic lobule
 +
aV inch. One of its surfaces is called the has
 +
It is by this surface that the lobule is set upc
 +
the wall of a sublobular vein, and the intr
 +
lobular or central vein, having emerged fro:
 +
the lobule through the centre of its bas
 +
 
 +
 
 +
 
 +
Fig. 515.—Section of
 +
the Liver, showing
 +
a Large Hepatic
 +
Vein and its Tributaries (after Kiernan).
 +
 
 +
 
 +
opens at once into the sublobular vein. The lobules, therefore, rel
 +
tively to the sublobular veins, on which they are ranged, are sessil
 +
When a sublobular vein is opened and viewed from within, an appearara
 +
something like mosaic work presents itself, the closely-set bases of tt
 +
lobules being visible through the thin wall of the vein, and the minut
 +
opening of the intralobular or central veins appearing in the centre (
 +
each base. Each lobule is composed of hepatic cells, permeated b
 +
capillary networks of bloodvessels and bile-capillaries.
 +
 
 +
Bloodvessels. —The liver derives its blood from two sources—namely
 +
the portal vein and the hepatic artery. These two vessels, togethe
 +
with the hepatic duct, are invested by the capsule of Glisson at th
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
885
 +
 
 +
>rtal iissure. Iheir several branches, ensheathed by prolongations of
 +
lisson's capsule, ramify from this point throughout the liver, being
 +
intained in the system of canals known as portal canals. Each of these
 +
nals contains (1) a branch of the portal vein, (2) a branch of the
 +
jpatic artery accompanied by a plexus of nerves, (3) lymphatic vessels,
 +
id (4) a minute duct, all these being loosely surrounded by a prolonuaDn of Glisson’s capsule.
 +
 
 +
The portal vein ramifies within the liver like an artery. In the
 +
irtal canals its branches receive as tributaries small capsular and
 +
ginal veins , and they go on ramifying until they arrive at the interbular areas. Here they anastomose freely with one another around
 +
e lobules, and so form the interlobular plexuses . The branches which
 +
ise from these plexuses enter the lobules on all sides except their
 +
tses, and form in the interior of each lobule an intralobular plexus.
 +
-om this plexus a few radicles converge towards the centre of the
 +
bule, where they form by their
 +
lion the intralobular or central vein.
 +
le portal blood, though dark in
 +
lour, is very rich, being derived
 +
Dm, amongst other sources, the
 +
Dmach and small intestine.
 +
 
 +
The hepatic artery is a branch of n
 +
e coeliac artery. As its branches
 +
iverse the portal canals they give
 +
f capsular branches to the fibrous
 +
psule of the liver, and vaginal
 +
inches, which supply the walls of
 +
e vessels in the portal canals, as
 +
ill as their Glissonian sheaths. The
 +
anches of the artery finally end
 +
minute interlobular arteries , which
 +
pply the walls of the interlobular
 +
 
 +
ins and bile-ducts. According to Fig. 516.—Two Hepatic Lobules
 +
me authorities they send minute (highly magnified).
 +
 
 +
pillary branches into the interior lobule showing the intralobular
 +
each lobule to join the mtra- plexus; B, lobule showing the
 +
 
 +
Dular plexus of the portal vein, but hepatic cells,
 +
 
 +
is view is not held by others.
 +
 
 +
The function of the hepatic artery and its branches is to nourish
 +
e tissues of the liver, whilst the portal blood supplies the materials
 +
fich are elaborated by the hepatic cells.
 +
 
 +
( The hepatic veins commence in the centre of each lobule as an
 +
ralobular or central vein. The intralobular veins open into the
 +
blobular veins, which are closely adherent to the bases of the lobules.
 +
 
 +
sublobular veins join to form larger sublobular veins, and these
 +
turn terminate in the hepatic veins, which are not in direct contact
 +
th the lobules. The hepatic veins pass to the fossa for vena cava on
 +
2 posterior surface of the liver, towards which they converge, taking
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
886
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
up sublobular veins in their course. The passages which contain t
 +
veins are known as the hepatic canals. On arriving at the upper p;
 +
of the fossa for vena cava they are reduced to two or three in numb
 +
which pour their contents directly into the inferior vena cava. It is
 +
be noted that the hepatic veins converge to the fossa on the poster
 +
surface, whilst the branches of the portal vein radiate in all directic
 +
from the portal fissure. The hepatic veins are accompanied only
 +
lymphatic vessels, and are surrounded by a very scanty amount
 +
areolar tissue, which explains why they present open mouths when c
 +
across.
 +
 
 +
Distinguishing Characters of the Hepatic and Portal Veins—Hepatic Veins
 +
 
 +
(i) These present open mouths when cut across. (2) They are accompan
 +
only by lymphatic vessels. (3) Their walls are very thin, and are practica
 +
in direct contact with the substance of the liver. (4) They converge towa:
 +
the caval fossa on the posterior surface.
 +
 
 +
Portal Veins. —(1) The mouths of these veins are practically closed or c
 +
lapsed when cut across. (2) The veins are accompanied by branches of
 +
hepatic artery, and by ducts. (3) Their walls are fairly thick, and are separa
 +
from the substance of the liver by the sheaths derived from Glisson’s capsi
 +
(4) They radiate in all directions from the porta hepatis in portal canals.
 +
 
 +
Hepatic Cells.— These are situated within the lobules. 1 hey c
 +
polyhedral, granular cells, having a diameter of T 7 T u_ inch, and ea
 +
contains a round nucleus. They have no cell-wall, properly so call*
 +
and they are connected by a delicate supporting tissue. Ihe ce.
 +
which are capable of amoeboid movement, lie between and around t
 +
capillary vessels, where they are arranged in radiating rows convergi
 +
towards the centre of the lobule.
 +
 
 +
Bile-ducts. —These commence within the lobules as bile-capillar
 +
or bile-canaliculi , which are in reality intercellular passages. Th
 +
have a very delicate wall, and are bounded on all sides by the hepa
 +
cells—hence the name intercellular passages. According to Pflih
 +
and Kupffer, the cells contain vacuoles, which communicate by int:
 +
cellular passages with the bile-capillaries. The hepatic cells intern
 +
between the bile-capillaries and the capillary bloodvessels. At t
 +
circumference of the lobule the bile-capillaries pass into the sm
 +
interlobular bile-ducts. These join to form larger ducts, and these
 +
turn go on joining until, on arriving at the porta hepatis, only t
 +
ducts result, which emerge one from each lobe. These now join to fo:
 +
the common hepatic duct, and this joins the cystic duct to form the bi
 +
duct. The walls of the interlobular ducts are very thin, being co
 +
posed of a basement membrane lined with polygonal epithelium. Tlarger ducts in the portal canals have thicker walls, which, from withe
 +
inwards, are composed of a fibro-elastic coat, containing plain muscu
 +
tissue, arranged longitudinally and circularly, and a mucous coat lir
 +
with columnar epithelium. The mucous membrane of the larger du<
 +
presents numerous openings, which lead into blind mucus-secreti
 +
recesses. The structure of the hepatic and bile-ducts is similar to t
 +
preceding, though on an increased scale.
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
v,HEP
 +
 
 +
 
 +
887
 +
 
 +
Lymphatics.—The lymphatic vessels of the liver are arranged in
 +
0 groups—superficial and deep.
 +
 
 +
Superficial Lymphatics.—These form plexuses beneath the perileal coat, and have different destinations.
 +
 
 +
Supero-anterior Surface. —(1) The lymphatics from the vicinity of
 +
3 falciform ligament enter that ligament, and, passing through the
 +
iphragm into the thorax, they terminate in the anterior group of the
 +
pradiaphragmatic glands. (2) The lymphatics from the right part
 +
the superior surface and those from the right lateral surface enter
 +
3 right triangular ligament, and,
 +
ssing through the diaphragm, they
 +
-minate in the middle group of the
 +
perior diaphragmatic glands of the
 +
r ht side. (3) The lymphatics from
 +
3 left part of the superior surface
 +
d those from the left extremity
 +
ter the left triangular ligament, and
 +
ss to the peri-cesophageal glands in
 +
ation to the lower end of the
 +
>ophagus, the efferent vessels of
 +
lich terminate in the cceliac glands.
 +
 
 +
1 The lymphatics from the anterior
 +
rt of the supero-anterior surface,
 +
cept those from the vicinity of the
 +
ciform ligament, turn round the
 +
terior border of the liver, and end
 +
the hepatic glands within the lesser
 +
lentum. (5) The lymphatics from ^ 517 ' Lymph Glands in the
 +
 
 +
e posterior surface of the right lobe Rouviere).
 +
ss between the two layers of the HEP, hepatic group,round the artery
 +
ronary ligament, and, having pierced and concerned with deep hepatic
 +
e diaphragm, they terminate in the
 +
na caval group of diaphragmatic
 +
mds within the thorax.
 +
 
 +
Inferior Surface. — (1) The lymtatics from the greater part of the
 +
ferior surface of the right lobe, intding those of the quadrate lobe,
 +
ss to the hepatic glands. (2) The lymphatics from the posterior
 +
ad of the inferior surface of the right lobe pierce the diaphragm,
 +
td end in the caval glands. (3) The lymphatics from the greater
 +
ad of the caudate lobe pierce the diaphragm, and end in the caval
 +
mds ; whilst those from the lower part of this lobe pass to the hepatic
 +
mds. (4) The lymphatics from the inferior surface of the left lobe
 +
ss to the hepatic glands.
 +
 
 +
Deep Lymphatics.—These vessels form two distinct sets. Some
 +
them accompany the branches of the portal vein, and having emerged
 +
rough the porta hepatis, they terminate in the hepatic glands. Others
 +
 
 +
 
 +
 
 +
drainage; B, a cystic gland above,
 +
and (below) a gland connected
 +
with this and with the retroduodenal gland ; D, above the
 +
head of pancreas. These glands
 +
are njore particularly concerned
 +
with the drainage of the system
 +
of biliary ducts.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
888
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
pass with the hepatic veins to the caval fossa of the liver, and thereal
 +
they enter the thorax along with the inferior vena cava, their destinat
 +
being the caval glands.
 +
 
 +
Nerves.—The nerves of the liver are derived from the hepatic plex
 +
which is an offshoot of the coeliac plexus. The coeliac plexus, thoi
 +
principally composed of sympathetic fibres, is reinforced by a 1
 +
twigs from the right vagus nerve. The hepatic plexus accompanies
 +
hepatic artery to the porta hepatis, where it receives branches from
 +
left vagus nerve, which have ascended from the antero-superior surf
 +
of the stomach between the two layers of the lesser omentum. In
 +
liver the nerves, which are chiefly non-medullated, are distributed
 +
the walls of the bloodvessels and ducts, penetrating as far as the inf
 +
spaces between the hepatic cells.
 +
 
 +
Development of the Liver.
 +
 
 +
Liver. —The hepatic cells and the epithelium of the bile-ducts are of er
 +
dermic origin, whilst the connective tissue of the gland and its vascular c
 +
stituents are developed from the mesoderm.
 +
 
 +
The rudiment of the liver appears as a longitudinal groove on the inner asp
 +
of the ventral wall of the duodenal portion of the primitive gut. This gro<
 +
 
 +
 
 +
 
 +
Fig. 518.— Sagittal Section through Septum Transversum and Caud
 +
End of Fore-gut in an Embryo of 4-5 Mm., to show Hepatic Divi
 +
 
 +
TICULUM AND GROWTH OF HEPATIC CYLINDERS AND GALL-BLADDER.
 +
 
 +
The cylinders have broken up the vitelline veins, represented here by the por
 +
vein, into sinusoids. The entoderm is shown by solid black.
 +
 
 +
gives origin to a diverticulum or evagination of the entoderm of the vent
 +
duodenal wall, called the hepatic diverticulum or liver-bud, which has at firsi
 +
wide communication with the gut. At a later period this communication becon
 +
constricted, and forms a pedicle, which, after undergoing elongation, gives r
 +
to the bile-duct. From this pedicle, close to the duodenal wall, the venti
 +
diverticulum of the pancreas arises.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
889
 +
 
 +
 
 +
The hepatic diverticulum or liver-bud invades the lower or caudal layer of
 +
septum transversum, composed of mesoderm, within which it bifurcates
 +
> two divisions, the right and left hepatic ducts.
 +
 
 +
The cells of these two divisions of the hepatic diverticulum undergo proration within the mesoderm of the lower layer of the septum transversum,
 +
thereafter each division breaks up into a number of solid trabeculae, which
 +
known as the hepatic cylinders. These cylinders give off secondary solid
 +
Deculae, and these again ramify extensively. The subdivisions of the various
 +
eeculae anastomose freely, and in this manner intricate networks are formed
 +
und the vitelline and umbilical veins, which veins traverse the septum
 +
isversum as they pass to the sinus venosus. The hepatic cylinders invade
 +
se veins, carrying the endothelial walls of the vessels before them. The
 +
is are thus freely subdivided into
 +
ad-channels, which are known as sinuIs. These sinusoids form capillary
 +
works, which occupy the meshes of
 +
net-works formed by the hepatic
 +
inders.
 +
 
 +
Many of the solid trabeculas become
 +
•ular, and give rise to the bile-capiles or bile-canaliculi, and bile-ducts.
 +
 
 +
iers give rise to the hepatic cells.
 +
 
 +
3 liver thus consists originally of incite reticula of solid cellular trabeculce,
 +
hepatic cylinders, disposed around the
 +
lline and umbilical veins.
 +
 
 +
As the liver increases in size it profs downwards, carrying with it the
 +
r er layer of the septum transversum,
 +
ich forms its capsule and connective
 +
;ue. The organ now lies between the
 +
a layers of the ventral mesentery,
 +
ich gives rise to—(1) the falciform
 +
iment; (2) the coronary ligament; and
 +
the lesser omentum (see p. 79).
 +
 
 +
About the middle of intra-uterine life
 +
: liver occupies a large part of the
 +
lominal cavity, and the right and left
 +
>es are of equal size. In the latter
 +
If of intra-uterine life, however, the
 +
ht lobe gradually attains greater size
 +
in the left. About the period of birth
 +
s liver extends almost as low as the
 +
ibilicus. After birth it undergoes dimition in size, the circulation of placental
 +
>od through it by the umbilical vein having been permanently arrested at
 +
th. The liver decreases in relative size largely owing to slower growth, but
 +
ire is also actual degeneration of part of its substance already formed. This
 +
plains the occurrence of degenerated remnants, vasa aberrantia and Kiernan s
 +
1 ules, found near its edge, in the left triangular ligament and by the inferior
 +
tia cava.
 +
 
 +
At an early period in development the liver has indications of four lobes,
 +
0 vitelline and two umbilical, but these are not so well marked as in some
 +
ier animals. The umbilical lobes form the two lateral lobes, but the vitelline
 +
)es are lost in the parts round the vena cava. The other small lobes on the
 +
; ceral surface are secondary, formed round large vessels or from surface relays; the free extremity of the caudate lobe has a small process which is the
 +
nnant of a part originally projecting into the bursa omentalis through its
 +
sning.
 +
 
 +
 
 +
 
 +
Fig. 519. —The Excretory Apparatus of the Liver.
 +
 
 +
G, gall-bladder; F, fundus; CD, cystic
 +
duct; H, common hepatic duct;
 +
B, bile duct; P, pancreatic duct;
 +
A, ampulla in duodenal wall into
 +
which both ducts open.
 +
 
 +
 
 +
 
 +
 
 +
8 go
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
The hepatic cylinders appear solid, but they contain no doubt poten
 +
lumina. These become apparent as bile-capillaries about the beginning of
 +
fourth month.
 +
 
 +
Hepatic lobules are not well formed before the first few years after bi]
 +
They are produced as a result of growth and branching of terminal twigs of
 +
hepatic veins, round which the cylinder cells group themselves, with their po
 +
vessels.
 +
 
 +
Structure of the Gall-bladder. —The wall of the gall-bladder
 +
composed of three coats—serous, fibro-muscular, and mucous.
 +
 
 +
The serous coat is formed by the peritoneum, and is usually inco
 +
plete, being confined to the inferior and lateral surfaces. Son
 +
times, however, the peritoneum completely surrounds the organ, a
 +
attaches its superior surface to the fossa for gall-bladder of the liver
 +
a ligamentous fold.
 +
 
 +
The fibro-muscular coat is composed of fibrous and plain muscu
 +
tissues. The fibrous bands are disposed in all directions, and int
 +
lace freely with one another. The muscular fibres, which int
 +
 
 +
mingle with the fibre
 +
bands, are arranged be
 +
longitudinally and trai
 +
versely. Around the t
 +
minations of the bile-di
 +
and pancreatic duct a
 +
their continuation ir
 +
the ampulla the circul
 +
muscular fibres are abr
 +
dant, forming the sphino
 +
of Oddi (Fig. 520).
 +
 
 +
The mucous coat
 +
covered by columnar ej
 +
tfiehum. Its surface presents a great number of small ridges, whi
 +
interlace in all directions and enclose polygonal depressions or alve
 +
of various sizes. This pitted appearance bears a resemblance
 +
honeycomb, and the mucous membrane of the seminal vesicle of t
 +
male is similarly arranged. The mucous coat is richly provided wi
 +
mucous glands. In the neck of the gall-bladder, which describes t\
 +
cui ves, there are two fibro-mucous folds, which project into the interie
 +
one opposite each curve, and serve as valves.
 +
 
 +
Structure of the Cystic Duct. —The wall of the duct is compos*
 +
of a fibro-elastic and muscular coat and a mucous coat. The form
 +
1 esembles that of the gall-bladder. The mucous coat, which is cover*
 +
Li' co ^ umnar epithelium, presents several crescentic folds dispos*
 +
obliquely round the wall in a spiral or somewhat corkscrew manne
 +
and succeeding each other at frequent intervals. When the duct
 +
distended, its exterior presents a series of spiral constrictions wii
 +
intervening swellings. The spiral folds in the interior serve as valve
 +
which are known as the spiral valve (valves of Heister).
 +
 
 +
Blood-supply. —The gall-bladder is supplied by the cystic arter
 +
which is a branch of the right division of the hepatic. Its cour:
 +
 
 +
 
 +
Sph. of Pancreatic Duct
 +
 
 +
 
 +
.Sph. of Bile Duct
 +
 
 +
 
 +
 
 +
r ^ Longitud. Fibres
 +
 
 +
Duodenal Pap.
 +
 
 +
Iug. 520.—Sphincter of Oddi (after
 +
 
 +
 
 +
Hendrickson).
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
891
 +
 
 +
 
 +
forwards between the hepatic and cystic ducts to the neck of the
 +
gan, where it divides into two branches, superior and inferior.
 +
ie superior branch ramifies on the upper surface of the organ, between
 +
and the fossa for gall-bladder of the liver, whilst the inferior branch
 +
distributed over the inferior surface beneath the peritoneum. The
 +
stic vein, which is formed by the union of superior and inferior
 +
anches, usually opens into the right division of the portal vein.
 +
>me of the veins from the gall-bladder may enter the liver to join
 +
e right branch of the portal vein. This fact explains the venous
 +
emorrhage which sometimes occurs when the gall-bladder is lifted
 +
it of its fossa.
 +
 
 +
Lymphatics. —These pass between the two layers of the lesser
 +
nentum to the hepatic glands.
 +
 
 +
Nerves. —These are derived from the hepatic sympathetic plexus.
 +
 
 +
Development of Gall-bladder and Duct.— An early stage is seen in Fig. 518.
 +
ie hepatic diverticulum is elongated in the line of the gut, and its lower end
 +
dilated to form the gall-bladder, the upper part alone giving origin to hepatic
 +
linders. The lower part of the groove is blocked by cell-growth, the bladder
 +
us opening into the upper part which will become the liver-duct. The bladder;
 +
latation grows ventrally in the mesoderm below the liver, its neck thus being
 +
retched out between the duct and the bladder, and becoming the cystic duct.
 +
 
 +
 
 +
Structure of the Pancreas.
 +
 
 +
The pancreas belongs to the class of compound racemose or acinolbular glands, and bears a close resemblance to a serous or true
 +
ilivary gland— e.g., the parotid. It has a greyish-pink colour, and
 +
somewhat soft in consistence. It is from 6 to 8 inches long, from
 +
to 1^ inches deep, except at the right and left extremities, and from
 +
to | inch thick. Its weight is about 3^ ounces. It is destitute of
 +
fibrous capsule, properly so called, and is invested merely by a thin
 +
onnective-tissue covering, which readily allows the outline of the
 +
)bules to be seen.
 +
 
 +
It is composed of a number of lobules, which are loosely held
 +
ogether by ducts and areolar tissue. Each lobule consists of a group
 +
f alveoli or acini which are long, tubular, and convoluted, wherein
 +
hey differ from the saccular alveoli of such a gland as the parotid.
 +
Tom each lobule a duct passes off, which unites with the ducts of
 +
djacent lobules in the left extremity of the gland to form the commencement of the principal duct. Within the lobule the lobular duct
 +
5 formed from junctional ducts, each of which belongs to an acinus,
 +
nd is lined with flattened cells.
 +
 
 +
The alveoli or acini are each composed of a basement membrane,
 +
eticular in structure, and lined with secreting columnar epithelium,
 +
he basement membrane being continuous with the wall of the junctional
 +
luct. The lumen of each acinus is small, and is usually occupied by
 +
pindle-shaped cells, known as the centro-acinar cells of Langerhans,
 +
vhich are continuous with the cells of the junctional duct, dhe
 +
 
 +
 
 +
892 A MANUAL OF ANATOMY
 +
 
 +
connective tissue which covers the pancreas sends expansions inw
 +
between the lobules, along which the bloodvessels are condu(
 +
Further, the interlobular connective tissue penetrates into the lob
 +
and so conducts the bloodvessels into their interior. The interalv i
 +
 
 +
connective tissue has a loose
 +
position, and in certain parts
 +
tains small groups of epithelium
 +
cells, surrounded by large convol
 +
capillary vessels. These gr<
 +
constitute the islets of Langerh
 +
which are characteristic of
 +
pancreas.
 +
 
 +
Excretory Apparatus of the 1
 +
creas. —There is one principal d
 +
called the pancreatic duct (due
 +
Wirsung). It is buried in the i
 +
stance of the gland, and is rea
 +
recognized by its white colour,
 +
lies nearer the posterior than
 +
anterior surface, and rather ne;
 +
the lower than the upper part of
 +
gland. It commences in the
 +
whence it runs through the b
 +
as far as the neck, receiving in
 +
course a great many tributai
 +
On arriving at the neck it eff<
 +
a communication with the ac<
 +
sory pancreatic duct, then descri
 +
a bend, and passes into the head in a direction downwards, backwai
 +
and to the right. Finally, on leaving the pancreas it meets the t
 +
duct, and the two, entering the wall of the second part of the duodem
 +
terminate in the manner already described (see p. 779).
 +
 
 +
The accessory pancreatic duct (duct of Santorini) is comparativ
 +
small, and varies much in size. If well developed, it commen
 +
in the lower part of the head, where it takes up the ducts of the lobi
 +
of that part. It then passes upwards with an inclination to the right, c
 +
divides into two branches. One of these joins the pancreatic main d 1
 +
in the neck, whilst the other opens into the second part of the duoden
 +
at a point about 1 inch above the common opening of the bile-di
 +
and the pancreatic duct. The secretion conveyed by the access(
 +
duct is believed in early life to flow into the duodenum, whereas in 1
 +
adult it is largely diverted into the pancreatic duct.
 +
 
 +
The tributaries of the principal duct, as well as of the accessc
 +
duct, when followed into the pancreas, become in succession int
 +
lobular and intralobular ducts. The intralobular ducts pass wit!
 +
the lobules, and end in intermediary , junctional, or intercalary* due
 +
with which the alveoli or acini are directly connected. The p£
 +
 
 +
Interposed or inserted between the alveoli and the intralobular ducts.
 +
 
 +
 
 +
Alveoli Islets of Langerhans
 +
 
 +
 
 +
 
 +
Fig. 521. — Structure of the
 +
Pancreas (highly magnified).
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
893
 +
 
 +
 
 +
he duct between the intermediary and the intralobular duct is
 +
3d the neck. The walls of the intermediary ducts are thin, and
 +
formed of a basement membrane covered by flattened epithelial
 +
5, the neck being lined by polyhedral cells. In the larger ducts
 +
Dnnective-tissue coat is superadded to the basement membrane,
 +
ch is now covered by columnar epithelium. The pancreatic duct,
 +
igh of comparatively large size, has a thin wall destitute of muscular
 +
3s except near its termination, and composed of two coats—
 +
irnal fibrous and internal mucous. The mucous coat is smooth and
 +
ered by columnar epithelium.
 +
 
 +
Varieties— (1) Small Pancreas. —This consists in a permanent detachment
 +
he unciform process, or that part of the pancreas which extends along the
 +
er aspect of the third part of the duodenum and has the superior mesenteric
 +
els in front of it. (2) The head of the pancreas may surround the second
 +
; of the duodenum more or less completely. (3) Accessory Pancreas.—
 +
;n an accessory pancreas is present it is usually met with in the wall of the
 +
 
 +
 
 +
Fig. 522.—The Pancreas and its Ducts (Posterior View).
 +
 
 +
A
 +
 
 +
>er part of the jejunum, but it may be found in the wall of the stomach or
 +
>er part of ileum. (4) The pancreatic duct sometimes opens into the duodenum
 +
3 pendently of, but close to, the bile-duct.
 +
 
 +
Blood-supply. —The pancreas derives its arteries from (1) the
 +
lcreatic branches of the splenic artery, one of which accompanies
 +
principal duct from left to right, and is known as the arteria panitic magna; (2) the superior pancreatico-duodenal of the gastro)denal from the hepatic; and (3) the inferior pancreatico-duodenal
 +
:he superior mesenteric.
 +
 
 +
The veins are (1) the pancreatic veins, which open into the splenic
 +
n; and (2) the pancreatico-duodenal veins, which terminate in
 +
; superior mesenteric or portal veins. All the pancreatic venous
 +
od eventually passes into the portal vein.
 +
 
 +
Lymphatics. —These commence as lymphatic clefts around the
 +
eoli, and pass chiefly to the cceliac glands. Some of them, however,
 +
minate first in the superior mesenteric glands in contact with the
 +
per part of the superior mesenteric artery.
 +
 
 +
Nerves. —These are derived from offshoots of the hepatic, splenic,
 +
i superior mesenteric plexuses, and accompany the arteries. They
 +
5 chiefly composed of non-medullated fibres.
 +
 
 +
 
 +
 
 +
Uncinate Process
 +
 
 +
 
 +
Pancreatic Duct
 +
 
 +
 
 +
Pancreatic Duct
 +
 
 +
 
 +
Accessory Duct
 +
 
 +
 
 +
Bile Duct
 +
 
 +
 
 +
 
 +
 
 +
894
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Development of the Pancreas. —The tubular portion of the pancreas
 +
entodermic origin, but its connective tissue and vascular elements are deve
 +
from mesoderm.
 +
 
 +
The pancreas is developed from two entodermic diverticula—dorsa
 +
ventral. The dorsal diverticulum is an evagination of the entoderm of the
 +
wall of the duodenal portion of the primitive gut. The ventral diverti(
 +
springs from the primitive hepatic diverticulum close to the ventral wall (
 +
duodenum, which diverticulum subsequently forms the bile-duct. The <
 +
diverticulum extends between the two layers of the meso-gastrium, wh
 +
comes into relation with the developing spleen. This diverticulum giv
 +
lateral epithelial tubes, which ramify freely, and so build up an acino-tu
 +
 
 +
 
 +
 
 +
Fig. 523. —Diagram to show the Relations of the Pancreatic
 +
Outgrowths to the Median Mesentery.
 +
 
 +
The dorsal wall of the duodenum is left on the meso-duodenum, and bet
 +
this and the oesophagus the stomach has been removed with the front
 +
of the bursa omentalis, leaving the posterior wall and opening of the
 +
The ventral outgrowth A is growing in the meso-duodenum, but the d
 +
growth, being higher up, is able to extend into the wall of the primitive
 +
The portal vein passes backwards, upwards, and to the right betweei
 +
two outgrowths.
 +
 
 +
gland. The acini appear as enlargements of the walls of the terminal t
 +
By means of the ramifications of the dorsal diverticulum the greater part o
 +
head, body, and tail of the adult pancreas are formed.
 +
 
 +
The ventral diverticulum is at first double, right and left outgrowths ar
 +
from the liver-hud. The left formation quickly disappears, while the right
 +
coming into relation with the portal vein, grows round this into the meso-duode\
 +
where it enlarges, being placed with the vein behind the duodenum as this ci
 +
out toward the right. It forms the pancreatic duct, and gives outgrowtl
 +
form the lower part of the head of the pancreas.
 +
 
 +
The ventral and dorsal parts of the pancreas join, and the dorsal d
 +
ticulum (pancreatic duct) and ventral diverticulum now communicate by fi
 +
anastomosing branches. Thereafter the duodenal portion of the pancr»
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
895
 +
 
 +
 
 +
ict usually atrophies and disappears. It may, however, persist, and open as
 +
l independent duct into the second part of the duodenum. The accessory
 +
iiicreatic duct is persistent, and constitutes the principal duct of the fully
 +
iveloped pancreas. From its mode of development it necessarily opens into
 +
e bile-duct.
 +
 
 +
The islets of Langerhans, which are characteristic of the pancreas, are formed
 +
cells derived from the walls of the original epithelial tubes. These cells become
 +
fferentiated, and by their multiplication they give rise to isolated cell-groups,
 +
ing in the mesodermic connective tissue between the lobules of the gland, where
 +
ey are soon permeated by bloodvessels.
 +
 
 +
The development of the head of the pancreas proceeds within the meso-duonum (Fig. 523) dorsal and caudal to the vitelline vein, which enters the mesolodenum here to form the beginning of the portal vein. The head, by its large
 +
owth, widens out the meso-duodenum to a very considerable extent, and
 +
oduces the curve of the duodenum round its mass. The body and tail of the
 +
gan extend into the dorsal wall of the bursa omentalis, growing rapidly in this
 +
ward the left. They thus come to be directed transversely, and are laid down
 +
the dorsal wall of the abdomen. When the peritoneum of this wall adheres
 +
the bursal wall, and the two adherent layers disappear, the gland is left in a
 +
ro-peritoneal position behind the completed lesser sac; rarely, however, the
 +
hesion and disappearance of the layers is incomplete, and thus a cyst may be
 +
:med behind the gland from fluid within a persisting part of the peritoneum
 +
re.
 +
 
 +
 
 +
Structure of the Spleen.
 +
 
 +
The spleen is the largest ductless gland in the body. It has two
 +
ats, serous and fibrous, inseparably connected together. The serous
 +
at is formed by the peritoneum. The fibrous coat or tunica propria
 +
composed of fibrous tissue, with a considerable admixture of elastic
 +
;sue, and a certain amount of plain muscular tissue, all of which
 +
lild up a strong distensible tunic.
 +
 
 +
The organ is composed of a trabecular network, the spleen pulp,
 +
oodvessels, and Malpighian corpuscles.
 +
 
 +
The tunica propria sends into the organ a number of trabecube
 +
fich, like the tunica propria, are composed of fibrous, elastic, and
 +
ain muscular tissues. These divide and subdivide, and unite with
 +
e another, as well as with processes derived from the sheaths which
 +
e bloodvessels carry in with them at the hilum. There is thus
 +
pied a trabecular network, which pervades the interior, and conins in its meshes the splenic pulp, capillary tufts, and lymphatic
 +
'dules.
 +
 
 +
The splenic pulp occupies the meshes of the network formed by the
 +
ibeculae. It is soft, and has a dark red colour, which, however,
 +
comes brighter on exposure to the air. The matrix of the spleen
 +
[ lp is reticular, and is formed by branched connective-tissue coracles, which constitute the sustentacular cells of the organ, the
 +
drix is, therefore, in reality retiform tissues. The interstices of
 +
e reticulum contain blood, in which there is a large number of white
 +
rpuscles, and also special cells characteristic of the spleen, and
 +
fied the splenic cells. These latter are of large size, and are amoeboid.
 +
iey contain pigment, and red blood-corpuscles in various stages of
 +
integration.
 +
 
 +
 
 +
8 g6
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Bloodvessels and Lymphatic Nodules (Malpighian Corpuscle!
 +
Arteries.—The splenic artery furnishes five or six large branches wl
 +
enter the organ at the hilum, and carry in with them trabecular shea
 +
from the tunica propria. In the interior they divide and subdiv
 +
and finally terminate in pencil-like clusters of capillary vessels,
 +
which time they have laid aside all their coats except the endotht
 +
lining. The endothelial cells then become separated from each ot
 +
by spaces, and being continuous with the sustentacular cells of
 +
spleen pulp, the blood flows directly into the interstices of the reticu]
 +
of the pulp. The arteries, which are at first accompanied by trabeci
 +
sheaths, ultimately lose these sheaths, and enter the splenic pulp
 +
 
 +
end in clusters of capillaries,
 +
fore they terminate in these c'
 +
ters their external coat underg
 +
an important modification, wl
 +
consists in its transformation i
 +
lymphoid or adenoid tissue. 1
 +
lymphoid tissue forms at inten
 +
small round or oval enlargemei
 +
called lymphatic nodules (Ma
 +
ghian corpuscles), which on sect
 +
appear as minute white speck;
 +
the dark red spleen pulp. Tb
 +
corpuscles are simply local!
 +
expansions of the lymphoid tis
 +
which forms the external coat
 +
the small arteries. The expans
 +
may be confined to one side
 +
the artery, or it may include
 +
whole of its circumference. E;
 +
corpuscle receives minute tv
 +
from the artery on which it is i
 +
and contains large numbers
 +
lymph corpuscles, as well
 +
capillary bloodvessels.
 +
 
 +
Veins.—The arterial blood, on leaving the capillary vessels, tie
 +
directly into the interstices of the reticular matrix of the spleen pr
 +
and from these it is taken up by radicle veins which commence b
 +
manner similar to that in which the capillaries end. Endothe
 +
cells, continuous with the sustentacular cells of the pulp, come togetl
 +
and cohere, so as to form very delicate tubular vessels having clo!
 +
walls. As these radicle veins unite and become larger the other co
 +
are superadded to the endothelial lining. Ultimately five or six ve
 +
leave the spleen at the hilum, which unite to form the splenic vei
 +
 
 +
this in turn uniting with the superior mesenteric vein to form the poi
 +
vein.
 +
 
 +
It is to be noted that, in the circulation through the spleen, j
 +
arterial blood leaves tubular vessels and flows through the interstij
 +
 
 +
 
 +
Capsule Trabecula
 +
 
 +
 
 +
 
 +
Lymphatic Nodules Splenic Pulp
 +
 
 +
 
 +
Fig. 524. —Section of the Spleen.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
897
 +
 
 +
 
 +
he reticulum of the spleen pulp, where it bathes the Malpighian
 +
niscles, after which it enters tubular vessels of the nature of veins,
 +
rhe cells of the spleen are of three kinds as follows: (1) the sustenilar cells of the retiform tissue of the spleen pulp; (2) the splenic>; and (3) lymphoid corpuscles.
 +
 
 +
Lymphatics. —These are arranged in two groups—trabecular and
 +
vascular. The trabecular lymphatics are contained in the trails, and communicate with a lymphatic network in the tunica
 +
pria underneath the peritoneal coat. The perivascular lymphatics
 +
mence in the lymphoid tissue which forms the external coat of
 +
smaller arteries. At the hilum both sets of lymphatics meet and
 +
3 to the splenic glands, and thence to the coeliac glands.
 +
 
 +
Nerves. —These are derived from the splenic plexus, which is an
 +
hoot from the coeliac plexus. The fibres, which are mostly nonLullated, are derived partly from the sympathetic system and partly
 +
n the right vagus nerve.
 +
 
 +
)evelopment of the Spleen. —The spleen is formed from the mesodermal
 +
of the bursa omentalis. In the fifth week the sac wall in its upper, dorsal,
 +
left part shows a certain amount of thickening, with vascularization, and
 +
2ase in size of the mesothelial cells covering its outer surface. A little later
 +
e covering cells proliferate, and cells pass from the layer into the mesenchyme
 +
le wall. As the mass enlarges it projects outwards into the peritoneal cavity.
 +
:he processes take place at several points the organ is lobed; although the
 +
d appearance is lost by subsequent fusion, the original divisions are indicated
 +
:he fissures. The cells arrange themselves in trabecular bands, and small
 +
gather round the small branches of the splenic artery and form the lymphatic
 +
lies (Malpighian corpuscles) about the seventh month. When the dorsal
 +
of the bursa omentalis becomes adherent to the wall of the abdomen, the
 +
sn, lying just outside the area of adhesion, is now attached to the outer edge
 +
his area by the intervening strip of non-adherent sqc wall— i.e., by what is
 +
wn as the lieno-renal fold. As it projects toward the left, away from the
 +
ty of the sac, it is covered by peritoneum of the greater sac, and is separated
 +
1 that of the lesser sac by the vessels in the wail of the latter.
 +
 
 +
 
 +
Structure of the Suprarenal Glands.
 +
 
 +
The suprarenal glands [adrenals) belong to the so-called ductless
 +
ids. Each gland is enclosed in a thin sheath of connective tissue,
 +
n the deep part of which processes are given off into the interior,
 +
ire they form a supporting stroma. The proper substance of the
 +
id is divided into an external or cortical, and internal or medullary
 +
t.
 +
 
 +
The cortex has a somewhat yellowish tint, due to the presence of
 +
poid substance, and is composed of cells supported by a fibrous
 +
)ma. The cells being variously arranged in different parts, the
 +
tex is divisible into three zones, named, from without inwards, zona
 +
nerulosa, zona fasciculata, and zona reticularis. The zona glomerul > which is narrow, lies immediately within the external capsule,
 +
I- is so named because its component cells are grouped in such
 +
tanner as to form glomeruli, which are embedded in a fibrous stroma.
 +
 
 +
57
 +
 
 +
 
 +
898
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
The cells are polyhedral, and each contains a clear round nucl
 +
The zona fasciculata forms the chief part of the cortex, and is so na]
 +
because its component cells are arranged in columns or fasciculi,
 +
cells are similar to those of the zona glomerulosa, and the cell coin
 +
are separated from one another by fibrous trabeculae, which aci
 +
carriers of the bloodvessels, nerves, and lymphatics. The zona ret
 +
laris, which is narrow, lies within the zona fasciculata, and is so nai
 +
because its component groups of polyhedral cells are connected \
 +
one another in such a manner as to form a reticulum.
 +
 
 +
The medulla is confi
 +
 
 +
 
 +
Capsule \
 +
 
 +
 
 +
Cortex
 +
 
 +
 
 +
Medulla
 +
 
 +
 
 +
 
 +
Zona Glomerulosa
 +
 
 +
 
 +
> Zona Fasciculata
 +
 
 +
 
 +
Zona Reticularis
 +
 
 +
 
 +
Fig. 525. —Section of the Suprarenal
 +
 
 +
Capsule.
 +
 
 +
 
 +
to the centre of the gl
 +
in the adult, is soft in c
 +
sistence, and has a redd
 +
brown colour, due to
 +
contained venous blood,
 +
supporting fibrous strom;
 +
the cortex pervades it, ;
 +
is arranged in a retici
 +
manner. The meshes of 1
 +
reticulum are occupied
 +
cells, larger and more irre
 +
lar than those of the corl
 +
further differing from tf
 +
in containing granules wf
 +
stain deeply with chromi
 +
salts.
 +
 
 +
Blood-supply—Arteries
 +
 
 +
These are (1) the supei
 +
suprarenal of the phre
 +
from the abdominal aoi
 +
(2) the middle suprare
 +
from the abdominal aoi
 +
and (3) the inferior sup
 +
renal from the renal.
 +
 
 +
The veins of each gh
 +
eventually unite to form <
 +
 
 +
 
 +
suprarenal vein. This vessel emerges through the hilum, and on
 +
right side it opens directly into the inferior vena cava, whilst on
 +
left side it terminates in the left renal vein.
 +
 
 +
The lymphatics terminate in the juxta-aortic glands . The lyi
 +
vessels accompany the vessels connected with the glands. T1
 +
issuing with the main vein drain the medullary region, and ]
 +
(Fig. 526) to aortic glands below the levels of the renal pedicles; on
 +
two pass behind these to glands behind the renal arteries. Yes
 +
accompanying the suprarenal arteries drain the cortex, and reach gla
 +
above the renal pedicles; on the right some pass behind the infe
 +
vena cava. Additional lymphatics, shown in the figure by interruj
 +
lines, run up on the diaphragm, which they pierce, to enter glands
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN 899
 +
 
 +
thoracic aorta at about the level of the ninth or tenth thoracic
 +
tebrae.
 +
 
 +
Nerves. —-The suprarenal glands are very richly supplied with nerves,
 +
ch are derived from (1) the phrenic plexus from the coeliac ganglion
 +
. coeliac plexus, (2) the suprarenal plexus from the coeliac ganglion
 +
. coeliac plexus, and (3) offshoots from the renal plexus. According
 +
Bergmann, the suprarenal glands also receive fibres from the phrenic
 +
. vagi nerves. The fibres, which are chiefly non-medullated, form
 +
l plexuses in the medulla, where they have numerous ganglion cells
 +
nected with them.
 +
 
 +
 
 +
 
 +
Fig. 526. —Lymphatics of Suprarenal Glands (after Rouviere).
 +
 
 +
Development. —The suprarenal gland makes its appearance medial to the
 +
•onephros. The cortex is of mesodermic origin, and the medulla is developed
 +
n the cells of the primitive abdominal sympathetic system.
 +
 
 +
The cortex is developed from cellular outgrowths of the mesothelium of the
 +
om, or body-cavity, on the mesial aspect of the mesonephros. These outwths soon become separated from the ccelomic mesothelium, and unite to
 +
n a solid mass, which constitutes the cortex.
 +
 
 +
The medulla is derived from the primitive abdominal sympathetic cells,
 +
'ups of cells grow out from the ganglia (these cells being consequently of
 +
Mermic origin), and they invade the cortex. They become differentiated
 +
^ two groups. The cells of one group are chromaffivi cells, and stain a dark
 +
ow colour with chromic acid salts. The cells of the other group are ganglion
 +
All the cells developed from the sympathetic ganglia gradually pass to the
 +
tre, where they constitute the medulla.
 +
 
 +
 
 +
 
 +
 
 +
900
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
The suprarenal gland thus develops in two parts—cortex, derived fron
 +
coelomic mesothelium (mesoderm), and medulla, derived from the abdor
 +
sympathetic ganglia, and therefore of ectodermic origin. The cortical
 +
begins to form in the fourth week, and the ganglion cells begin their inv:
 +
three weeks later; the process goes on till after birth, and ill-understood fc
 +
tive changes continue for some years.
 +
 
 +
Structure of the Kidneys.
 +
 
 +
The kidneys are compound tubular glands. Each organ is
 +
vested by a capsule, composed of fibrous tissue with a certain aim
 +
of elastic fibres. The deep surface of this capsule is attached tc
 +
peripheral portion of the renal substance by fine fibrous processes
 +
 
 +
small bloodvessels. Ur
 +
neath it there is a cei
 +
amount of plain muse
 +
fibre, arranged in a sc
 +
what plexiform manner,
 +
the hilum on the inner bo
 +
it is prolonged inwarck
 +
line a cavity to which
 +
hilum leads, called the t
 +
sinus, where it becomes
 +
tinuous with the fibrous c
 +
of the calyces.
 +
 
 +
When a kidney is
 +
into two halves by a lc
 +
tudinal incision carried f
 +
the outer to the inner bo
 +
it is seen to be comp<
 +
of two parts—cortex
 +
medulla.
 +
 
 +
The medulla, whicl
 +
internal in position, is
 +
ranged in conical bum
 +
termed renal pyramids (pyramids of Malpighi), which vary in nun
 +
from eight to eighteen, the average number being about twe
 +
The bases of these pyramids are directed towards the circumfere:
 +
whilst their apical parts, called renal papillae, project into the sinus, wl
 +
they are grasped by the calyces. Each renal pyramid is divided :
 +
three parts—namely, the basal part, the papillary zone, and the a ;
 +
The basal parts of the pyramids form collectively the boundary zon
 +
the kidney. They abut against the cortical substance, which se
 +
prolongations between them, called renal columns (columnar BerU
 +
These prolongations extend as far as the commencement of the ap
 +
parts of the papillary zones, where they cease, so that these ap
 +
parts project into the calyces free from cortical investments. E
 +
renal pyramid is composed of straight, slightly converging urinifei
 +
tubules (tubuli recti ) and straight bloodvessels, the number of tub
 +
 
 +
 
 +
Renal Pyramid
 +
 
 +
 
 +
 
 +
Calyx
 +
 
 +
 
 +
-Pelvis
 +
 
 +
 
 +
— Ureler
 +
 
 +
 
 +
Fig. 527.—Diagram of the Kidney in
 +
Longitudinal Section.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
901
 +
 
 +
 
 +
ig very much greater in the basal part than elsewhere. This
 +
ight arrangement of tubules and bloodvessels imparts to each
 +
amid a longitudinally striated appearance from apex to base. The
 +
al parts have a dark reddish-brown colour, which becomes brighter
 +
he papillary zones.
 +
 
 +
The cortex of the kidney is mainly situated within the fibrous
 +
sule. It has a reddish-brown colour, and, as already stated, sends
 +
longations between the renal pyramids. Like the medullary part,
 +
; composed of uriniferous tubules and bloodvessels, but the tubules
 +
principally convoluted (tubuli contorti), though there are also
 +
dies of straight tubules (tubuli recti) which have issued from the
 +
il pyramids, and form the medullary rays.
 +
 
 +
Cortex. —The cortical part is composed of the labyrinth and the
 +
lullary rays.
 +
 
 +
Labyrinth .—This portion of the cortex is so named from the very
 +
iplicated arrangement of its tubules. It is situated in the internes between the medullary rays, and is composed of convoluted
 +
dferous tubules, bloodvessels, and glomeruli, each of the latter being
 +
losed within a capsule of Bowman.
 +
 
 +
Uriniferous Tubules. —Each tubule commences in the labyrinth
 +
he cortex in a spherical dilatation, called the capsule of Bowman,
 +
tiin which there is a tuft of convoluted capillary bloodvessels, known
 +
i Malpighian glomerulus (Malpighian corpuscle). Bowman s capsule
 +
sents two poles. One of these is formed by two bloodvessels, afferent
 +
efferent, which pierce the capsule at separate points, but close to each
 +
er. At the other pole Bowman’s capsule becomes constricted, and
 +
ns the neck of a cylindrical tubule. After the tubule has passed the
 +
k it becomes convoluted, and forms the first convoluted tubule. The
 +
 
 +
 
 +
sment membrane and lining epithelium of Bowman’s capsule are conious with the basement membrane and lining epithelium of the first
 +
voluted tubule, and the space between Bowman’s capsule and the
 +
nerulus is continuous with the lumen of the tubule. The first
 +
voluted tubule soon becomes straight, though slightly wavy, and,
 +
Ting a medullary ray, it forms the spiral tubule. This tubule, on
 +
'hing the junction of the cortex and boundary zone, becomes
 +
denly very narrow, and traverses the basal part of a renal pyramid,
 +
s known as the descending limb of Henle’s loop. On leaving the
 +
ndary zone it enters the papillary zone, and after a short course
 +
escribes a very sharp bend, called the loop of Henle. It now re'es its steps from the papillary zone into the boundary zone of a
 +
al pyramid, in which latter situation it becomes suddenly enlarged,
 +
s part, which retraces its steps, is called the ascending limb of Henle’s
 +
»• It re-enters the cortex, where it becomes narrower, and passes
 +
> a medullary ray, in which it lies for a short distance. It subaently, however, leaves the ray, and, entering the labyrinth,
 +
ds between the convoluted tubules as the irregular or zigzag tubule,
 +
ch has become slightly enlarged. This irregular tubule then passes
 +
1 the second convoluted tubule. This tubule, becoming narrow,
 +
 
 +
 
 +
go2
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
passes into the junctional tubule, which is slightly wavy. The
 +
tional tubule leads into the straight or collecting tubule, which is slij
 +
enlarged, and is situated in a medullary ray. This straight colle
 +
tubule now passes to the basal part of a renal pyramid, taking i
 +
 
 +
 
 +
 
 +
Fig. 528. —Diagram of the Uriniferous Tubules of the Kidney (Ki
 +
 
 +
a and a', outer and inner zones of cortex, which are free from
 +
 
 +
Malpighian bodies.
 +
 
 +
1. 1. Capsule of Bowman 4. 4. Spiral Tubule
 +
 
 +
2. 2. Neck of Capsule 5. 5. Descending Limb of Henle’s Loop
 +
 
 +
3. 3. First Convoluted Tubule 6 6. Loop of Henle
 +
 
 +
7. 7., 8. 8., 9. 9., Ascending Limb of Henle’s Loop
 +
 
 +
10. 10. Irregular Tubule 13. 14. Collecting Tubule
 +
 
 +
11. 11. Second Convoluted Tubule 15. Duct of Bellini
 +
 
 +
12. 12. Junctional Tubule
 +
 
 +
 
 +
its course other junctional tubules from the labyrinth. In pa
 +
through the various parts of a renal pyramid the collecting tu
 +
unite at acute angles, and so become less numerous and at the same
 +
larger. They run in straight, slightly converging lines toward
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
903
 +
 
 +
 
 +
x of a papilla, where they are very much reduced in numbers, but of
 +
(e size. In this final part of their course each collecting tubule
 +
ns the duct of Bellini. These excretory tubes open on the apex of
 +
ipilla, where there is often a foveola or small depression, and through
 +
se openings the urine escapes into a calyx.
 +
 
 +
The diameter of the ducts of Bellini is about inch.
 +
 
 +
Summary of a Tubule from Beginning to End.
 +
 
 +
[. The capsule of Bowman, containing a glomerulus in the labyrinth .
 +
 
 +
>. The neck, in the labyrinth.
 +
 
 +
5. The first convoluted tubule, in the labyrinth.
 +
j.. The spiral tubule, in a medullary ray.
 +
 
 +
5. The descending limb of Henle’s loop (small), in a basal part, and in part
 +
papillary zone, of a renal pyramid.
 +
 
 +
). The loop of Henle, in a papillary zone.
 +
 
 +
7. The ascending limb of Henle’s loop (large), in part of a papillary zone, a
 +
l part, and the cortex, in which latter it is in a medullary ray.
 +
 
 +
The irregular or zigzag tubule, in the labyrinth.
 +
 
 +
). The second convoluted tubule, in the labyrinth.
 +
 
 +
:o. The junctional tubule, in the labyrinth on its way to a medullary ray.
 +
 
 +
[i. The collecting tubule, in a medullary ray of the cortex, and in a basal part
 +
renal pyramid.
 +
 
 +
[2. The duct of Bellini, in a papillary zone of a renal pyramid.
 +
 
 +
Structure of the Uriniferous Tubules. —The tubules are composed of a baset membrane lined with a single layer of epithelial cells. The basement
 +
ibrane itself consists of flattened epithelial cells. The tubules vary in
 +
but their average diameter may be stated as inch. The characters
 +
he lining epithelial cells present differences in the different tubules, which
 +
now be considered in order.
 +
 
 +
[. The capsule of Bowman is lined with a single layer of flattened epithelium,
 +
:h is reflected over the glomerulus, where it is more distinct in early life than
 +
ie adult.
 +
 
 +
-• The neck is lined with cubical epithelium.
 +
 
 +
5. The first convoluted tubule is also lined with cubical epithelium, but the cells,
 +
:h are thick, are peculiar. The inner part of each cell—that is, the part next
 +
lumen of the tubule—including the spherical nucleus, has granular protoplasm,
 +
st the outer part—that is, the part next the basement membrane—has its
 +
pplasm striated or fibrillated, owing to the presence of rod-shaped fibrils disposed
 +
ically to the basement membrane (Heidenhain). These fibrillated cells are
 +
dded laterally with processes by which they embrace one another. The
 +
en of the tubule is distinct.
 +
 
 +
p The spiral tubule is lined with epithelium similar ’to that of the first* conned tubule, and its lumen is distinct.
 +
 
 +
5- The descending limb of Henle’s loop is lined with clear, thin, flattened cells.
 +
tubule, though narrow, has a distinct lumen.
 +
 
 +
5 . The loop of Henle is lined with epithelium which resembles that of the
 +
lending limb.
 +
 
 +
7- The ascending limb of Henle’s loop is lined with fibrillated, cubical epithelial
 +
like those of the first convoluted and spiral tubules. Though it is of comffively large size, its lumen is small.
 +
 
 +
3 - The irregular or zigzag tubule is lined with cubical epithelial cells, which
 +
markedly fibrillated, and its lumen is minute.
 +
 
 +
3 - The second convoluted tubule is lined with epithelium which resembles
 +
t of the first convoluted tubule, with the following differences: (a) the cells
 +
longer; and (b) they are highly refractive. In size it corresponds with the
 +
' convoluted tubule.
 +
 
 +
 
 +
 
 +
9o 4 A MANUAL OF ANATOMY
 +
 
 +
10. The junctional tubule is lined with clear, flattened, cubical epithelial ,
 +
and its lumen is large.
 +
 
 +
11. The collecting tubule is lined with epithelial cells, which in its earlier
 +
are clear and cubical, but in its later part they are columnar, and the lum<
 +
very distinct.
 +
 
 +
12. The duct of Bellini is lined with epithelial cells which are clear
 +
 
 +
columnar.
 +
 
 +
Medullary Rays or Pyramids of Ferrein. —These take the torn
 +
pyramidal bundles of uriniferous tubules, which are separated f:
 +
each other by portions of the labyrinth. The tubules are straij
 +
and emerge from the basal parts of the pyramids. As these medul]
 +
rays are followed from the basal parts to the periphery, each gradu
 +
diminishes in breadth, and ultimately tapers to a point, which si
 +
a short distance from the fibrous capsule, being separated from it
 +
a portion of the labyrinth. The rays are thus conical, their bases b(
 +
at the basal parts of the renal pyramids, and their apices near the fibi
 +
capsule—hence the name ‘ pyramids.’ The explanation of this sh
 +
is that the tubules at the circumference of a medullary ray enter
 +
labyrinth sooner than those in the centre, which latter form the a
 +
of the ray.
 +
 
 +
Summary of a Medullary Ray. —Each contains the following tubules: (i) sj
 +
tubules; (2) ascending limbs of Henle’s loops; and (3) collecting tubules.
 +
 
 +
Medulla of the Kidney. —The medullary portion has been alre;
 +
generally described. It is composed of renal pyramids, consisl
 +
of uriniferous tubules and bloodvessels (true and false).
 +
 
 +
The tubules in the various parts of the renal pyramids are as folio
 +
 
 +
1. Basal Part. —This contains the following tubules:
 +
 
 +
Portions of the descending limbs of Henle’s loops.
 +
 
 +
Portions of the ascending limbs of Henle’s loops.
 +
 
 +
Collecting tubules.
 +
 
 +
2. Papillary Zone. —This contains the following tubules:
 +
 
 +
Portions of the descending limbs of Henle’s loops.
 +
 
 +
The loops of Henle.
 +
 
 +
Portions of the ascending limbs of Henle’s loops.
 +
 
 +
The ducts of Bellini.
 +
 
 +
3. Apex of the Papillary Zone. —This contains only the ducts
 +
Bellini.
 +
 
 +
Bloodvessels of the Kidneys — Arteries. —Each kidney receives
 +
large amount of blood from the renal artery, which is a branch of
 +
abdominal aorta. This vessel, as it approaches the hilum, divides i]
 +
four or five branches, which enter the sinus, where they are embedc
 +
in fat along with the calyces. They then subdivide into interlo'
 +
branches, which pass between the renal pyramids, where they contir
 +
to subdivide. On arriving at the junction of the cortex and bound;
 +
zone they form a series of arches, which are independent of one anotb
 +
and are called the cortico-medullary arches. Alongside of these th<
 +
are venous arches, which, unlike the arterial arches, anastomose fre<
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
905
 +
 
 +
 
 +
ith one another. The convexities of the incomplete arterial arches
 +
;e directed towards the cortex, and the concavities towards the renal
 +
yramids. The branches of the arches are interlobular and arteriae
 +
;ctae.
 +
 
 +
The interlobular arteries (cortical) arise from the convexities of the
 +
rches and enter the labyrinth of the cortex, in which they pass outards between the medullary rays,
 +
hey give off afferent and capsular
 +
ranches.
 +
 
 +
The afferent branches are so named
 +
ecause they carry blood to the
 +
'omeruli. They arise from the in^rlobular arteries at frequent interals, and each passes to a capsule
 +
f Bowman without giving off any
 +
ranch. Having pierced the capsule
 +
t one pole, the afferent vessel breaks
 +
p into a number of convoluted
 +
ipillary vessels, which form a small
 +
ascular ball, called a glomerulus
 +
Malpighian corpuscle). The blood is
 +
onveyed away from the glomerulus
 +
y an efferent vessel, which is variously
 +
sgarded as an artery and a vein,
 +
his efferent vessel is smaller than
 +
tie afferent artery. It pierces
 +
bowman’s capsule at the same pole
 +
s the afferent artery, but separate
 +
:om, though close to, it. Therefter it breaks up into a network of
 +
apillary vessels, which invest the
 +
orresponding first convoluted urinierous tubule, the meshes of the network being polygonal. The efferent
 +
r essels of those glomeruli which lie
 +
learest to the renal pyramids are
 +
iisposed in a different manner. They
 +
>reak up into bundles of straight
 +
vessels, called false vasa recta, which
 +
nter the basal parts of the pyramids,
 +
diere they supply to a large extent the uriniferous tubules, upon the
 +
mils of which they form capillary networks with elongated meshes,
 +
t is, however, to be noted that the renal pyramids also receive true
 +
irterise rectae from the cortico-medullary arterial arches.
 +
 
 +
The Glomerulus (Malpighian Corpuscle). —A glomerulus of the kidney
 +
s a small ball of convoluted capillary bloodvessels, having two vessels
 +
connected with it, one of which is an afferent artery and the other an
 +
'fferent vessel. The vessels of many of the glomeruli are collected into
 +
 
 +
 
 +
 
 +
VESSELS OF THE KlDNEY.
 +
 
 +
A, cortex; B, medulla.
 +
 
 +
1. Arterial Arch
 +
 
 +
2. Interlobular Artery
 +
 
 +
3. Afferent Artery of Glomerulus
 +
 
 +
4. Capsular Branches
 +
 
 +
5. Efferent Vessel of Glomerulus
 +
 
 +
6. Glomerulus
 +
 
 +
7. First Convoluted Tubule
 +
 
 +
8. True Arteria Recta
 +
 
 +
9. False Arteria Recta
 +
 
 +
10. Venous Arch
 +
 
 +
11. Interlobular Vein
 +
 
 +
12. Venae Stellatae
 +
 
 +
13. Venae Rectae
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
9o6 A MANUAL OF ANATOMY
 +
 
 +
bundles, an arrangement which renders these glomeruli tabulated,
 +
number of lobules varying from two to five. Each glomerulus
 +
within a capsule of Bowman, and the flattened epithelium of the caps
 +
is reflected over the glomerulus from the points of entrance and exil
 +
the afferent and efferent vessels. The epithelial cells covering the c
 +
puscle are thicker and less flattened than those lining the capsule
 +
Bowman, and are better marked in early life than in the adult,
 +
the case of the tabulated glomeruli the epithelial investment dips
 +
between the component lobules. The epithelium of Bowman’s caps
 +
and the epithelium of the glomerulus, which in each case forms a sin
 +
layer, are separated from one another by a slight interspace. 1
 +
 
 +
diameter of a glomerulus is about ¥ To * n
 +
The glomeruli are confined to the cortex of i
 +
kidney, where they lie in rows in the labyrii
 +
between the medullary rays. There is a narr
 +
zone immediately within the external capsi
 +
and another narrow zone close to the re:
 +
pyramids, from both of which glomeruli ;
 +
absent.
 +
 
 +
The capsular branches of the interlobu
 +
arteries supply the external fibrous capsule
 +
the kidney, in which they anastomose w:
 +
branches of the lumbar arteries from the c
 +
dominal aorta.
 +
 
 +
The arteriae rectae (medullary), or vasa rec
 +
(true), arise from the concavities of the corti(
 +
medullary arterial arches, and at once enter t
 +
basal parts of the renal pyramids. Here th
 +
break up into bundles of straight, sligh
 +
diverging arterioles, which run between t
 +
bundles of straight, slightly converging uri:
 +
ferous tubules, a mutual arrangement whi
 +
imparts to the renal pyramids a longitudina
 +
striated appearance. The capillary networ
 +
formed by these arterioles have necessar:
 +
elongated meshes. It is to be noted that t
 +
renal pyramids derive their blood-supply frc
 +
two sources—namely, (i) the arteriae rectae, or vasa recta (true), frc
 +
the cortico-medullary arterial arches; and (2) the false vasa recta frc
 +
the efferent vessels of those glomeruli which lie nearest the rer
 +
pyramids. It is also to be noted that a glomerulus of the kidney is
 +
ball of convoluted capillary bloodvessels, which is enclosed with
 +
a capsule of Bowman, whereas a Malpighian body of the spleen is
 +
collection of lymphoid or adenoid tissue which is a localized expansi<
 +
of the external or lymphoid coat of the small arteries in the interi
 +
of that organ.
 +
 
 +
Veins — Veins of the Cortex. —These are called the interlobular vein
 +
Some of them commence on the surface of the kidney beneath tl
 +
 
 +
 
 +
 
 +
showing a Glomerulus OF THE
 +
Kidney with its
 +
Afferent and Efferent Vessels,
 +
and a Proximal
 +
Convoluted Tubule with ITS
 +
Venous Plexus
 +
(Bowman).
 +
 
 +
1. Glomerulus
 +
 
 +
2. Bowman’s Capsule
 +
 
 +
3. Uriniferous Tubule
 +
 
 +
4. Interlobular Artery
 +
 
 +
5. Afferent Vessel
 +
 
 +
6. Efferent Vessel
 +
 
 +
7. Venous Plexus around
 +
 
 +
Tubule
 +
 
 +
8. Interlobular Vein
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
907
 +
 
 +
 
 +
psule, from which they return blood, and these are called vence stellatce,
 +
cause the venous radicles which give rise to them converge to a
 +
int, and so present a star-like appearance. Others originate in the
 +
sxuses around the uriniferous tubules. The interlobular veins
 +
rminate by joining the convexities of the venous arches, which are
 +
uated between the cortex and the renal pyramids.
 +
 
 +
Veins of the Medulla. —The veins of the renal pyramids commence
 +
plexuses which surround the ducts of Bellini in the apical parts of the
 +
pillary zones, and they are called vencB rectcB. As these traverse the
 +
aamids they are collected into bundles of straight vessels, which
 +
ien into the concavities of the cortico-medullary venous arches.
 +
 
 +
Cortico-medullary Venous Arches. —These arches, which are comste, are situated between the cortex and the renal pyramids, where
 +
ey lie alongside of the incomplete arterial arches. They derive their
 +
Dod from the interlobular veins of the cortex and the venae rectae
 +
the renal pyramids. The veins which proceed from these arches
 +
„ss between the pyramids to the sinus of the kidney, where they
 +
Lite to form the renal vein, which terminates in the inferior vena cava.
 +
Lymphatics. —These consist of two groups, superficial and deep,
 +
le superficial lymphatics, which are few in number, form a plexus in
 +
e fibrous capsule, and communicate with lymph spaces between the
 +
iniferous tubules in the outer part of the cortex. They terminate
 +
r joining the deep lymphatics at the hilum. The deep lymphatics
 +
company the bloodvessels, and communicate with lymph spaces
 +
itween the uriniferous tubules of the cortex and boundary zone,
 +
n emerging at the hilum they receive the superficial lymphatics,
 +
id then pass to the juxta-aortic group of lumbar glands.
 +
 
 +
Nerves. —The kidney receives numerous nerves from the renal
 +
exus, which derives its fibres from (1) the aortico-renal ganglion,
 +
which the lesser splanchnic nerve terminates; (2) the coeliac plexus;
 +
id (3) the aortic plexus. If there is a lowest splanchnic nerve present
 +
reinforces the renal plexus. The nerve-fibres are partly sympathetic,
 +
irtly spinal through the lesser and lowest splanchnic nerves, and in
 +
irt derived from the right vagus through the coeliac plexus. I hey
 +
^company the arterial branches, and ramify upon the walls of the
 +
sssels and uriniferous tubules.
 +
 
 +
Excretory Apparatus of the Kidney. —This consists of the calyces,
 +
 
 +
elvis, and ureter.
 +
 
 +
Ureter. —This is the excretory duct of the kidney, and it has the
 +
>rm of a cylindrical tube, like a goose-quill, its colour being a dull
 +
hite. Its length varies from 12 to 16 inches, and its diameter is
 +
bout 1 inch. At its lower extremity it opens into the bladder, and
 +
t the hilum of the kidney it joins the pelvis of the kidney, which is
 +
mnel-shaped, being wide above and narrow below. Ihe pelvis is
 +
attened from before backwards, and lies partly in the sinus and
 +
artly outside the hilum, its direction being downwards and inwards,
 +
t is formed by the union of two or three primary divisions or greater
 +
alyces (infundibula) within the sinus, and these again are formed by
 +
 
 +
 
 +
9o8
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
the union of about nine secondary divisions, called lesser calyces. 1
 +
number of lesser calyces thus usually falls short of the number of re
 +
pyramids (8 to 18), the explanation being that one lesser calyx n
 +
grasp two papillae or even three. The lesser calyces embrace i
 +
papillae of the renal pyramids, which thus project into them, and tl
 +
receive the urine as it oozes through the pores on the apices of 1
 +
papillae, these pores being the openings of the ducts of Bellini. 1
 +
interspaces between the lesser calyces in the renal sinus are occup;
 +
by the branches of the renal bloodvessels and by fat.
 +
 
 +
Structure of the Ureter. —The ureter is a thick-walled muscu
 +
tube, lined with mucous membrane, and consists of three coats
 +
external or fibrous, middle or muscular, and internal or muco’
 +
 
 +
 
 +
Middle Circular Muscular Fibres
 +
 
 +
 
 +
Outer Longitudinal Muscular Fibres
 +
 
 +
 
 +
 
 +
53 1 • Transverse Section of the Lower Part of the Ureter,
 +
showing its Minute Structure.
 +
 
 +
 
 +
The fibrous coat is composed of fibrous tissue, very compactly arrange^
 +
and contains the bloodvessels and nerves, which here subdivide. Tl
 +
muscular coat is composed of plain muscular tissue, which is dispose
 +
in three layers —outer longitudinal, middle circular, and internal long
 +
tudinal. The outer longitudinal layer is best marked in the lower ha
 +
of the ureter, where it forms a continuous investment. In the uppf
 +
half of the tube its bundles are somewhat scattered. The mucoi
 +
coat superiorly is continued over the papillae of the renal pyramids, an
 +
interiorly becomes continuous with the mucous membrane of tb
 +
bladder. It is covered by stratified transitional epithelium, the celbeing arranged in four layers. In the most superficial layer (nearer
 +
the lumen of the tube) the cells are cubical, and present depressions o
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
909
 +
 
 +
 
 +
eir deep surfaces, which receive the round ends of the pyriform cells
 +
the layer beneath. In the second layer the cells are pyriform, the
 +
und superficial ends being capped by the cubical cells of the first
 +
^er, and the narrow deep ends projecting between the deeper cells,
 +
the third and fourth layers the cells are round or oval. The mucous
 +
smbrane is thrown into longitudinal folds, and the lumen of the
 +
be, which is of small size, presents under the microscope a branched
 +
•pearance on cross-section.
 +
 
 +
Around the lower end of the ureter for a distance of 3 or 4 mm.
 +
a fibrous-tissue covering known as Waldeyer’s sheath. Between
 +
is sheath and the ureteral wall proper is some loose bursal tissue,
 +
lich serves to facilitate the slight but important movement which
 +
kes place between the lower end of the ureter and the vesical wall
 +
contraction and relaxation of the bladder, and which has for its
 +
irpose the prevention of regurgitation of urine.
 +
 
 +
Blood-supply—Arteries. —The ureter receives branches from the
 +
nal, testicular (ovarian in the female), common iliac, and superior
 +
:sical arteries.
 +
 
 +
The veins terminate in the vessels corresponding to these arteries.
 +
Lymphatics. —These pass to the juxta-aortic group of lumbar glands ,
 +
Ld to the internal iliac glands.
 +
 
 +
Nerves. —These accompany the arteries, and are derived from
 +
e renal, testicular (ovarian in the female), and pelvic plexuses. The
 +
)res form plexuses in the fibrous and muscular coats, which contain
 +
lall ganglia.
 +
 
 +
Structure of the Pelvis and Calyces. —The structure of these parts
 +
the excretory apparatus resembles that of the ureter, with the
 +
:ception that they have only two layers of plain muscular tissue,
 +
stead of three as in the ureter. The layer which is wanting is the
 +
tier longitudinal layer. The lesser calyces are attached to the bases
 +
the papillae, and in these situations their fibrous coats become coniuous with that part of the fibrous capsule of the kidney which is
 +
'olonged inwards through the hilum to line the sinus. The internal
 +
ngitudinal muscular fibres disappear towards the papilla, but the
 +
rcular muscular fibres accompany a lesser calyx to its termination,
 +
here they are arranged in the form of a circular band, which surrounds
 +
base of a papilla at the line of attachment of a calyx. The stratified
 +
ansitional epithelium of the mucous coat of a lesser calyx is pronged over the apex of each papilla.
 +
 
 +
Stroma of the Kidneys. —Between the uriniferous tubules and
 +
oodvessels there is a certain amount of connective tissue, which
 +
present in greatest abundance in the region of the papillary zones,
 +
his constitutes what is known as the fibrous or intestinal stroma,
 +
which there is a very small amount.
 +
 
 +
Early Condition of the Kidneys. —The kidneys of a child at the period of birth
 +
e lobulated, each lobule representing a renal pyramid surrounded by cortical
 +
bstance. In this respect they resemble the permanently lobulated kidneys of
 +
rtain animals— e.g., the ox. The lobules first become apparent towards the
 +
 
 +
 
 +
 
 +
 
 +
9io
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
end of the third month of intra-uterine life, and all traces of them have usi
 +
 
 +
 
 +
disappeared by the eighth or tenth year.
 +
 
 +
 
 +
 
 +
Fig. 532. —-Kidney of a Child shortly
 +
before Birth.
 +
 
 +
 
 +
They may, however, remain persh
 +
to a greater or less extent throug
 +
life, though this condition is of
 +
rare occurrence. It is, however,
 +
uncommon to find the surface o
 +
adult kidney marked by faint gro
 +
indicative of its original lobul
 +
condition. The disappearance of
 +
lobulated condition is brought a’
 +
by the adjacent lobules coalescing,
 +
being accompanied by an incre
 +
development of cortical substanc
 +
the surface. The portions of cor
 +
substance which remain in the sp
 +
between the renal pyramids (ex
 +
their apical parts) form the r
 +
columns.
 +
 
 +
 
 +
Development of the Kidney and Ureter.
 +
 
 +
The metanephros, or permanent kidney, is the last of the serie:
 +
excretory organs formed in the human embryo. For the acco
 +
of these organs, see p. 94 et seq.
 +
 
 +
The ureteric bud, the earliest formation in association with
 +
metanephros, begins to grow from the mesonephric duct when
 +
embryo is about 5 mm. long. It is a club-shaped, hollow outgrow
 +
which (Fig. 533) is surmounted from an early stage by a blastemal c
 +
formed by metanephric mesoderm. The markedly condensed d
 +
or inner layer of this cap is a very noticeable feature. The hoi
 +
outgrowth elongates fairly rapidly, growing in a cranial directi
 +
dorsal to the mesonephros, and carrying its blastemal cap on
 +
extremity as it grows. The bulbous end soon divides into two, c
 +
from these secondary outgrowths take place, each process carrying
 +
own blastemal cap upon it. In this way the cavities of the gret
 +
and lesser calyces are marked out. The process continues of elongat
 +
of outgrowth, subdivision, and consequent new outgrowths, and so
 +
and thus the collecting tubes of the kidney are made, each advanc
 +
end being covered by its metanephric cap of blastemal tissue.
 +
 
 +
At a later stage the earliest formed generations of these collecting-t
 +
systems are taken up into the calyces, so that the final number of collecting tu
 +
is not the same as the whole number formed, and more tubes come to open i
 +
the calyces directly than originally grew from them.
 +
 
 +
the formation of outgrowths goes on during the second, thi
 +
and fourth months, and probably for a considerable time after tl
 +
About the beginning of the third month, however, some of the tul
 +
subdivisions have reached their terminal stages, and the blasten
 +
caps of these terminal outgrowths begin to show activities whi
 +
ultimately lead to the formation of the secretory parts of the tubi
 +
system. 1 he inner zone of the cap forms a solid mass of cells, whi
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
911
 +
 
 +
>n becomes hollow, and is termed the renal vesicle. A curved short
 +
mle grows from this towards the bent end of the terminal collecting
 +
>e, with which it becomes connected. The renal vesicle is in the
 +
antime invaginated, and thus constitutes a glomerulus. The short
 +
■ved tubule, somewhat in the shape of an S, elongates slowly. The
 +
 
 +
 
 +
 
 +
Fig. 533. —Schematic Drawings to illustrate the Formation of
 +
the Tubular System of the Kidneys.
 +
 
 +
A the ureteric outgrowth is shown arising from the mesonephric duct close to
 +
where this enters the cloaca. The enlarged end of the bud is covered by its
 +
blastemal cap. The enlarged end becomes bilobed. B, each lobe covered by
 +
its cap. Further subdivisions are seen in C. Terminal subdivisions are
 +
shown in D, where the cap is forming, on the left, a rounded ‘ renal vesicle/
 +
R.V. On the right a tubule is growing from the vesicle toward the end of the
 +
collecting terminal. In E and F the tubule has fused with the terminal,
 +
and by elongating is making convoluted tubules and a loop of Henle. A
 +
vascular loop V grows against the renal vesicle and the adjoining part of
 +
its tubule, and invaginates them, producing a glomerulus.
 +
 
 +
'ond convoluted tubule is formed from the upper limb of the curve,
 +
s first convoluted tubule from its lower limb, and the intervening
 +
rtion is lengthened into Henle’s loop. Henle’s loops can be disL °tly recognized during the fourth month. The other descriptive
 +
rts of the system of tubules are gradually formed as elongation pn>
 +
isses.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
912
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
It is seen, then, that the tubule system, from the glomerulus to i
 +
arched collecting duct, is derived from the metanephric mesodei
 +
while the whole system of collecting ducts is formed by outgrov
 +
from the original ureteric growth. The junction between the t
 +
parts of the whole tubule system is effected shortly after the blaster
 +
tubule begins its growth; it is the failure of this junction which ir
 +
lead to one of the varieties of congenital cystic kidney.
 +
 
 +
The secondary junction between outgrowths from the mesonephric duct on
 +
one hand, and tubules formed separately in the mesoderm on the other ha
 +
is not in itself an extraordinary or out-of-the-way occurrence. It is well knc
 +
to occur in several species of animals, and it is apparently represented in
 +
development of the secondary tubules of the human mesonephros, which, wl
 +
 
 +
 
 +
Suprarenal Glands
 +
 
 +
 
 +
 
 +
Fig. 534. —The Mesonephro, Mesonephric, and Para-mesonephric Due
 +
 
 +
and Contiguous Parts (Allen Thomson).
 +
 
 +
they are formed, extend toward the mesonephric duct, and meet secondary p
 +
jections from this duct in their direction. In the case of the metanephros t
 +
may, in the light of what has just been said, be looked on as corresponding w
 +
these secondary tubules of the mesonephros coming into relation with enormou
 +
elongated outgrowths from the mesonephric duct.
 +
 
 +
The vascular constituents, the interstitial connective-tissue stroma,
 +
renal columns, and the renal capsule are developed from the metanephric blaster
 +
 
 +
The ureter of either side, which originally opens into the uro-genital sii
 +
in common with the mesonephric duct, becomes detached from that duct a
 +
opens by an independent orifice into the uro-genital sinus on its dorsal aspe
 +
It may here be stated that the urinary bladder is developed from the u
 +
genital sinus.
 +
 
 +
Summary. —The pronephros is functional in lower vertebrates— e.g., cert;
 +
Fishes, and Amphibia during the larval stage. In Man it is rudimentary, d
 +
pronephric duct persists as the mesonephric duct.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
913
 +
 
 +
 
 +
Pronephros'
 +
 
 +
 
 +
Diaphragmatic - Ligament of
 +
Pri/nit/t/e /t/cfney
 +
 
 +
 
 +
Mesoneph .
 +
' M( sorter hr
 +
Duct
 +
 
 +
 
 +
 
 +
Duct of Epoophoron
 +
 
 +
 
 +
Prostatic
 +
 
 +
Utricle
 +
 
 +
 
 +
6/rooep/fai
 +
S/pus fi/est/pp/e)
 +
 
 +
 
 +
535 -—Development of the Uro-genital System (after Heisle).
 +
 
 +
 
 +
58
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
914
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
The mesonephros or Wolffian body succeeds to the pronephros, and pe
 +
as the functional kidney in Fishes and Amphibia. In Man it atrophies
 +
large extent, and is replaced by the metanephros.
 +
 
 +
The metanephros is the permanent human kidney.
 +
 
 +
THE PELVIS.
 +
 
 +
The pelvis is the lower division of the abdomen which lies b
 +
the level of the pectineal lines and sacral promontory. Unlike
 +
abdomen proper, the walls of the pelvis are chiefly osseous,
 +
posterior wall is constructed by the sacrum and coccyx, with the ori
 +
of the pyrif ormes muscles. Each lateral wall is formed by the body
 +
spine of the ischium, and is covered by the obturator internus mu
 +
 
 +
 
 +
Pelvic Colon Gt. Omentum
 +
 
 +
 
 +
 
 +
Fig. 536. —Transverse Section at Level of Lumbo-sacral Junction
 +
 
 +
(after Symington).
 +
 
 +
 
 +
The anterior wall is formed by the bodies of the pubic bones, whicJ
 +
the median line construct the symphysis pubis. Between the poste:
 +
wall and each lateral wall is a large space, which is partly closed by
 +
powerful sacro-tuberous and sacro-spinous ligaments. This spact
 +
divided into two parts by the sacro-spinous ligament and the spin(
 +
the ischium. The upper part forms the greater sciatic foramen, wb
 +
transmits the pyrif ormis muscle; the superior gluteal vessels, lymphat
 +
and nerves; the inferior gluteal vessels, lymphatics, sciatic nerve, <
 +
posterior cutaneous nerve of thigh; the internal pudendal vessels c
 +
lymphatics and pudendal nerve; the nerve to the obturator inter]
 +
and gemellus superior; and the nerve to the quadratus femoris c
 +
gemellus inferior. The lower part forms the lesser sciatic foram
 +
which transmits the obturator internus muscle and its nerve, 1
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
915
 +
 
 +
rnal pudendal vessels, and the pudendal nerve. At each lateral
 +
t of the anterior wall is the obturator foramen, which is closed,
 +
-pt superiorly, by the obturator membrane, covered by the obturator
 +
rnus muscle. Below the symphysis pubis is the pubic arch, which
 +
•ccupied by the perineal membrane. The pelvic wall, thus conicted, is clothed by the pelvic fascia. Superiorly the pelvic cavity
 +
uite open and in free communication with the abdomen proper,
 +
jrioily it is for the most part closed, a complex septum separating
 +
rom the perineum underneath. This septum is partly muscular
 +
partly fascial. The muscles entering into it are the levatores ani
 +
the coccygei, which construct the pelvic diaphragm. The fascial
 +
rent is formed on either side by the visceral pelvic fascia, which
 +
hes the superior or pelvic surface of the muscular diaphragm, and
 +
the anal fascia, which covers its inferior or perineal surface. The
 +
 
 +
 
 +
 
 +
Fig. 537. —Male Pelvic Region seen from Above.
 +
 
 +
 
 +
r of the pelvis is consequently movable, being capable of ascending
 +
descending. It affords passage to the rectum and urethra, and, in
 +
ition, in the female to the vagina.
 +
 
 +
Contents of the Pelvis. —The contents of the male pelvis are as
 +
 
 +
)ws: the pelvic colon and rectum; the bladder, with the lower
 +
tions of the ureters and the prostate gland, the latter containing
 +
prostatic part of the urethra; the seminal vesicles and the lower
 +
tions of the vasa deferentia; the internal iliac vessels and their
 +
fiches; portions of the superior rectal and median sacral vessels;
 +
rectal, vesical, and prostatic venous plexuses, the latter receiving
 +
dorsal vein of the penis in two divisions; the sacral and coccygeal
 +
uises and their branches; the pelvic portions of the gangliated
 +
ip a thetic trunks; and the obturator nerves in part of their course.
 +
The differences in the contents of the female pelvis, as compared
 +
h those of the male, are as follows:
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
916
 +
 
 +
For the prostate gland and prostatic portion of the urethra sul
 +
tute the female urethra, uterus, and vagina. For the seminal vesi
 +
and portions of the vasa deferentia substitute the broad ligament
 +
the uterus and their contents—namely, the uterine tubes, the ova
 +
with their ligaments, and the ligamenta teres of the uterus. Ad<
 +
portions of the superior rectal and median sacral vessels portions of
 +
ovarian vessels. For the prostatic venous plexus substitute the pu<
 +
dal plexus, and add the uterine and ovarian venous plexuses.
 +
 
 +
 
 +
THE MALE PELVIS.
 +
 
 +
 
 +
General Position of the Viscera. —The pelvic colon and reel
 +
are situated upon the posterior wall, the pelvic colon reaching as lo\
 +
the third sacral vertebra, and the rectum extending thence downwa
 +
 
 +
 
 +
 
 +
Comm. Iliac a. 1 ** 11 **** 1
 +
 
 +
Ureter- •
 +
 
 +
Lumbo-sacral Trunk
 +
Ext. Iliac A.
 +
 
 +
 
 +
Obtur. N
 +
 
 +
Sup. Ves. A
 +
 
 +
Obtur. A
 +
 
 +
Vas Def
 +
Lat. Umbil. Lig.
 +
 
 +
 
 +
 
 +
 
 +
Fig. 538. —Structures on Side Wall of Male Pelvis.
 +
 
 +
 
 +
and forwards to the interval between the levatores ani muscles, wh<
 +
it is succeeded by the anal canal. The bladder is anterior in positi<
 +
being situated behind the bodies of the pubic bones, and resting by
 +
base upon the rectum. The seminal vesicles and the lower portions
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
917
 +
 
 +
 
 +
vasa deferentia lie in contact with the base of the bladder, between
 +
nd the rectum. The prostate gland surrounds the prostatic part
 +
he urethra.
 +
 
 +
Peritoneum. —The disposition of the peritoneum will be simplified
 +
iefining the limits of the pelvic colon and rectum, and the different
 +
ts of the bladder. The pelvic colon extends from the inner border
 +
he left psoas major, just anterior to the left sacro-iliac articulation,
 +
he level of the third sacral vertebra. The rectum extends from the
 +
d sacral vertebra to a point t\ inches in front of and below the tip
 +
he coccyx, where it pierces the pelvic diaphragm to terminate in
 +
anal canal, which is the part of the large gut surrounded by the
 +
incter muscles. The bladder, when empty, presents the following
 +
ts: (1) an apex, which is directed forwards, and lies behind the upper
 +
 
 +
 
 +
 
 +
Pelvic Colon
 +
 
 +
i
 +
 
 +
/
 +
 
 +
Line of Peritoneal Reflection
 +
Ureter
 +
 
 +
t- Vas Deferens
 +
 
 +
Seminal Vesicle
 +
Bladder
 +
 
 +
/ Urachus
 +
 
 +
 
 +
Symphysis Pubis
 +
 
 +
 
 +
Levator Ani (cut) /
 +
 
 +
 
 +
Anus
 +
 
 +
 
 +
Corpus Cavernosum
 +
, Corpus Spongiosum
 +
Bulb and Bulbo-spongiosus
 +
' Deep Layer of Sup. Perineal Fascia
 +
» Perineal Pouch
 +
Membranous Urethra
 +
Bulbo-urethral Gland
 +
Prostate Gland and Capsule
 +
 
 +
 
 +
Perineal Membrane
 +
 
 +
 
 +
Fig. 539.— The Viscera of the Male Pelvis (Lateral View).
 +
 
 +
 
 +
: of the symphysis pubis, where it has connected with it the median
 +
rilical ligament lepresenting the urachus; (2) a fundus (base) or
 +
terior surface, directed backwards and downwards towards the
 +
■um, from which it is separated by the seminal vesicles and vasa
 +
irentia; and (3) a body which has a superior and two infero-lateral
 +
aces. Four borders are described, two being lateral, and serving
 +
separate the superior and infero-lateral surfaces; one posterior,
 +
mating the fundus from the superior surface, and stretching between
 +
two ureters as they pierce the bladder wall; and one faintly marked
 +
mior border, which separates the two infero-lateral surfaces. The
 +
:er enters the bladder at the junction of the fundus with the superior
 +
infero-lateral surfaces at what is known as the lateral angle.
 +
 
 +
The peritoneum, having descended from the posterior wall of the
 +
omen over the common iliac vessels, enters the back part of the
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
918
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
pelvic cavity, where it invests the pelvic colon, forming behind il
 +
expanded, wavy mesentery, called the pelvic meso-colon, which attac
 +
it to the front of the sacrum as low as the third sacral vertebra. '
 +
peritoneum is then prolonged upon the rectum, the upper third of wl
 +
it covers anteriorly and laterally , but not posteriorly, the middle t!
 +
being covered by it only anteriorly , whilst the lower third is destil
 +
of peritoneal covering. The point at which the peritoneum leaves
 +
rectum is fully 3 inches above the anus. The membrane is now can
 +
forwards to the upper ends of the seminal vesicles and the adjac
 +
portions of the vasa deferentia, which it covers. It then pa:
 +
forwards over the superior surface of the bladder, which it comple
 +
 
 +
 
 +
Pelvic Colon Bladder
 +
 
 +
 
 +
 
 +
Fig. 540. —Transverse Section through the Second Sacral Vertebr
 +
 
 +
(after Symington).
 +
 
 +
 
 +
covers as far as the apex. Here it meets the median umbilical ligame
 +
and by this is conducted from the bladder to the posterior surface
 +
the anterior abdominal wall. Along each lateral border of the blad<
 +
the peritoneum is reflected over the corresponding lateral wall of 1
 +
pelvis. In passing from the rectum to the upper part of the base
 +
the bladder the peritoneum forms the recto-vesical pouch. The both
 +
of this pouch is, as a rule, fully 1 inch distant from the base of 1
 +
prostate gland, thus leaving the part of the base of the bladder, cat
 +
the external trigone, quite free from peritoneum. The peritoneum,
 +
it passes to and from the bladder, forms certain folds, which constiti
 +
the false ligaments of the viscus. These are five in number as follow
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
919
 +
 
 +
 
 +
posterior , which represent the laterally-disposed lips of the mouth
 +
;he recto-vesical pouch; two lateral, right and left, which represent
 +
reflection of peritoneum from each lateral border of the bladder
 +
the corresponding lateral wall of the pelvis; and superior, which
 +
he reflection of the peritoneum from the apex of the bladder to
 +
posterior surface of the anterior abdominal wall along the median
 +
bilical ligament. The parts of the bladder which are left uncovered
 +
peritoneum are (1) the inferior surface, and (2) the external trigone.
 +
 
 +
The pelvic peritoneum on either side of the bladder and rectum presents
 +
recesses when these viscera are moderately distended, which are named,
 +
a before backwards, paravesical and pararectal.
 +
 
 +
Retro-pubic Cellular Tissue. —This is a collection of areolar and
 +
pose tissues which lies between the posterior aspect of the bodies
 +
:he pubic bones, the bladder, and medial pubo-prostatic ligaments.
 +
Pelvic Fascia. —This fascia clothes the inner wall of the pelvis, and
 +
lishes inward expansions, which have an intricate connection with,
 +
 
 +
 
 +
Parietal Pelvic Fascia
 +
 
 +
Visceral Pelvic Fascia
 +
Levator Ani
 +
Anal Fascia
 +
Obturator Internus
 +
Parietal Pelvic Fascia
 +
 
 +
 
 +
i | v —*
 +
 
 +
Prostate Gland, with Urethra Pudendal Canal..
 +
 
 +
Fig. 541.—The Pelvic Fascia (Anterior View).
 +
 
 +
1 serve to support, the contained viscera. It is divisible into two
 +
'tions—parietal and visceral.
 +
 
 +
Parietal Portion .—Over the posterior wall of the pelvic cavity
 +
: parietal portion of the pelvic fascia, which is here very thin, covers
 +
1 intrapelvic portion of each pyriformis muscle and the corresponding
 +
ral plexus, this portion being known as the fascia of the pyriformis.
 +
er the lateral wall the fascia attains considerable strength, and is
 +
ached superiorly to the back part of the iliac portion of the pectineal
 +
3 for a short distance, where it becomes continuous with the iliac
 +
cia. In front of this the fascia falls short of the pectineal line, and
 +
ixed to the lateral wall of the pelvis a little below the line, its attachnt being oblique, and accurately following the upper border of the
 +
turator internus muscle. When it arrives at the upper part of the
 +
turator foramen there is a break in the osseous attachment of the
 +
cia, which here joins the upper border of the obturator membrane
 +
sr the upper border of the obturator internus, and so converts the
 +
turator groove into a canal for the passage of the obturator vessels
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
920
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
and nerve. At the upper and inner part of the obturator foramen
 +
fascia resumes its osseous attachment, but falls more and more st
 +
of the pelvic margin, its connection with the back of the body of
 +
os pubis being in a direction downwards and inwards till it reac
 +
a point just below the lower part of the symphysis pubis. The fas
 +
descends from the foregoing line of attachment, closely covering
 +
obturator internus, to be attached as follows from before backwar
 +
(i) to the pelvic aspect of the ischio-pubic ramus near the pubic ar
 +
medial to the obturator internus; (2) to the inner margin of the falcifc
 +
process of the sacro-tuberous ligament at the lower part of the iscl
 +
ramus, and also to the sacro-tuberous ligament itself, where thai
 +
attached to the inner margin of the ischial tuberosity; and (3) t<
 +
portion of the sacro-tuberous ligament near its ischial attachment, e
 +
to the anterior margin of the greater sciatic notch The lateral port
 +
of the parietal pelvic fascia, from its relation to the obturator inten
 +
 
 +
 
 +
Parietal Pelvic Fascia
 +
 
 +
 
 +
Levator Ani..
 +
 
 +
Anal Fascia
 +
 
 +
Obturator Internus..-N$!/
 +
Parietal Pelvic Fascia-''
 +
 
 +
Pudendal Canal
 +
 
 +
 
 +
Visceral Pelvic Fascia
 +
 
 +
 
 +
 
 +
--- Seminal Vesicle
 +
 
 +
 
 +
Vas Deferens
 +
 
 +
 
 +
h J G. 542. —Diagram of the Pelvic Fascia from Behind.
 +
 
 +
 
 +
muscle, is sometimes called the obturator fascia. From its lower attac
 +
ment the fascia is continued backwards and inwards over the great
 +
sciatic foramen, pyriformis, and sacral plexus to the sacrum, as t.
 +
fascia of the pyriformis. As it covers the foramen it is perforated 1
 +
the superior and inferior gluteal, and internal pudendal vessels, and
 +
m consequence indistinct.
 +
 
 +
At the anterior part of the pelvic cavity the fascia, after takii
 +
attachment to the pelvic surface of the ischio-pubic ramus near t]
 +
pubic arch, is continued inwards over that arch, where it lies behii
 +
the sphincter urethrae muscle, and forms one half of the superior lay
 +
ot the perineal membrane, the other half being formed by the corr
 +
spondmg portion of the fascia of the opposite side. When it arrives ;
 +
the urethra it changes its course, and passes backwards over the anterii
 +
border of the levator ani to blend with that portion of the visceral pelv
 +
fascia which ensheathes the prostate gland.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
921
 +
 
 +
 
 +
In the direction of a line passing from the inner aspect of the ischial
 +
ine to the back of the body of the os pubis, near its lower end and close
 +
the symphysis, the lateral pelvic fascia is strengthened by fibres
 +
dch impart to it a white colour. This part is called the arcus tenleus [white line), and it serves to divide the fascia into two portions—
 +
per or pelvic proper, and lower or perineal. The pelvic portion
 +
)ks into the pelvic cavity, and covers the upper part of the obturator
 +
:ernus, whilst it is itself covered by the peritoneum. The perineal
 +
rtion covers the lower part of the obturator internus, and lies on the
 +
ter wall of the ischio-rectal fossa, where it constructs the pudendal
 +
rial. The under aspect of the arcus tendineus affords extensive
 +
[gin to the levator ani muscle.
 +
 
 +
Visceral Portion of the Pelvic Fascia. —The visceral portion is
 +
stined to support the lower part of the bladder, seminal vesicles,
 +
rminal portions of the vasa deferentia, prostate gland, and rectum,
 +
is a laminar offshoot of the parietal portion, from which it springs
 +
mg the arcus tendineus. Though, however, this is its principal
 +
urce, it has an independent origin anteriorly on either side of the
 +
ddle line from the posterior aspect of the body of the os pubis near
 +
e lower part of the symphysis. In this latter situation it lies a little
 +
ove the attachment of the parietal portion, the anterior fibres of the
 +
rator ani taking origin from the portion of bone between the two
 +
seise. Though the visceral portion forms one continuous sheet along
 +
pelvic attachment, its ultimate disposition is so intricate that it is
 +
nvenient to consider its arrangement under three divisions.
 +
 
 +
1. Opposite the bladder, seminal vesicle, and rectum. In this region
 +
e visceral portion of the fascia passes inwards as far as the outer
 +
rder of the seminal vesicle. In doing so it covers the upper surfaces of
 +
e levator ani and coccgyeus, and is in turn covered by the peritoneum.
 +
 
 +
the outer border of the seminal vesicle it divides into three laminae—'per, middle, and lower. The upper or vesical lamina ascends upon
 +
e lateral aspect of the bladder for a short distance, and ultimately
 +
>es itself in the muscular tissue of the vesical wall. This portion at
 +
ch side forms the lateral pubo-prostatic ligament of the bladder. The
 +
ddle or recto-vesical lamina passes inwards between the base of the
 +
idder and the rectum, and is continuous with the corresponding
 +
nina of the opposite side. As it passes inwards it furnishes a sheath
 +
the seminal vesicle and adjacent portion of the vas deferens, closely
 +
'apping these structures to the base of the bladder. The lower or
 +
3tal lamina descends upon the side of the rectum, and passes to its
 +
sterior surface, where it is continuous with the rectal lamina of the
 +
posite side.
 +
 
 +
2. Opposite the lateral aspect of the prostate gland. I11 this situa>n the visceral portion of the fascia also divides into three laminae
 +
upper, middle, and lower. The upper or prostatic lamina passes
 +
vards over the anterior surface of the prostate gland, and is congous with the prostatic lamina of the opposite side. The middle
 +
recto-prostatic lamina passes inwards between the posterior surface
 +
 
 +
 
 +
922
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
of the prostate gland and the rectum, and is continuous with
 +
corresponding lamina of the opposite side. The lower or rectal lam
 +
is unaltered in its disposition. The upper or prostatic and middle
 +
recto-prostatic laminse furnish a stout sheath to the prostate gland.
 +
 
 +
3. Between the pubic bodies and the anterior aspect of the pros
 +
gland. The portion of the visceral fascia in this region represe
 +
the upper lamina in the other regions, and may be called the pu
 +
prostatic lamina. It is arranged in the form of two stout cords, wb
 +
are known as the medial pubo-prostatic ligaments or the anterior i
 +
ligaments of the bladder. Each is attached anteriorly to the poste]
 +
aspect of the body of the os pubis, near the lower part of the symphy
 +
and a little above the attachment of the parietal portion of the pe]
 +
fascia in this region, the anterior fibres of the levator ani taking ori
 +
from the portion of bone between the two fasciae. As the cord -1
 +
fascial bands pass backwards they are connected by a portion of
 +
visceral fascia which covers the dorsal vein of the penis and lies deef
 +
thus giving rise to a small pouch, which is capable of admitting ■
 +
point of a finger. This pouch is filled with fat, which is continuous w
 +
the retro-pubic pad of fat. The anterior portion of the visceral fas
 +
lies upon the anterior surface of the prostate gland, and on reach
 +
the bladder it passes forwards on its inferior surface, where it sc
 +
disappears in the muscular tissue of the vesical wall. The mec
 +
pubo-prostatic ligaments are largely composed of plain muscular tiss
 +
which is derived from the longitudinal fibres on the inferior surface
 +
the bladder as they pass to take attachment to the back of the bod
 +
of the pubic bones on either side of the middle line. These fib
 +
constitute the so-called pubo-vesical muscles.
 +
 
 +
Anal Fascia. —This very thin sheet of fascia is an offshoot fr<
 +
the parietal pelvic fascia just below the white line and the origin
 +
the levator ani. It closely covers the ischio-rectal surface of tl
 +
muscle and of the coccygeus, upon which it descends to the region
 +
the anus, where it blends with the aponeurotic investment of t
 +
sphincter ani externus.
 +
 
 +
Sympathetic Plexuses in the Pelvis. —These are derived from t
 +
hypogastric plexus, which is formed by the fusion of the two latei
 +
strands of the aortic plexus after they have crossed the common ili
 +
arteries. It is reinforced by branches from the ganglia of the lumb
 +
sympathetic trunks, and is situated in front of the body of the fif
 +
lumbar vertebra between the common iliac vessels. It is a lar£
 +
flattened plexus, measuring about ij inches in breadth, and breaks 1
 +
into two divisions, which form the right and left pelvic plexuses. Ea<
 +
of these enters the pelvis on the inner side of the internal iliac arte
 +
and takes up a position on the side of the rectum. The pelvic plexi
 +
of each side is reinforced by branches from the upper one or two gangl
 +
of the pelvic sympathetic trunk, and by spinal fibres from the anter!
 +
primary divisions of the third and fourth sacral nerves (sometimes at
 +
the second), there being very small ganglia at the places of junctio
 +
From each plexus the following secondary plexuses are given off, whic
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
923
 +
 
 +
 
 +
xompany the corresponding branches of the internal iliac artery:
 +
aemorrhoidal, vesical, and prostatic, the latter being replaced in the
 +
male by the vaginal and uterine plexuses.
 +
 
 +
Internal Iliac Artery. —This vessel arises from the common iliac
 +
Dposite the sacro-iliac joint at the level of the lumbo-sacral joint,
 +
id terminates opposite the upper border of the greater sciatic notch
 +
y.dividing into an anterior and a posterior division. The length of
 +
le vessel is about ij inches, and its direction is downwards and
 +
ickwards.
 +
 
 +
Relations — Anterior. —The artery is covered by the peritoneum,
 +
id the ureter descends over it. In front of the ureter are the ovary
 +
id the fimbriated extremity of the uterine tube. The terminal part
 +
i the ileum forms an anterior relation of the right vessel, whilst the
 +
dvic colon is similarly related to the left. Posterior. —The vessel
 +
‘sts chiefly upon its own vein, but near its origin it is placed over the
 +
)mmencement of the common iliac vein. Behind the veins there are
 +
le lumbo-sacral trunk and sacro-iliac joint. Lateral. —The psoas
 +
tajor, with the intervention of the external iliac vein, and subsequently
 +
le lateral wall of the pelvis, with the intervention of the obturator
 +
srve. Medial. —The peritoneum.
 +
 
 +
Varieties. —The chief variety affects the length of the vessel. It may be
 +
lorter or longer than usual, according as the common iliac is longer or shorter
 +
lan normal, or according to the height at which the internal iliac ends in its
 +
vo divisions.
 +
 
 +
Foetal Condition. —During foetal life the internal iliac is represented by the
 +
mbilical artery, the size of which greatly exceeds that of the external iliac. The
 +
mction of this artery is to carry the impure blood from the foetus to the placenta
 +
: the mother. The umbilical artery passes forwards to the posterior surface of
 +
le anterior wall of the abdomen, being crossed by the vas deferens. It then
 +
scends to the lower part of the umbilicus, where it leaves the abdomen with its
 +
llow. The two umbilical arteries, together with the umbilical vein, form the
 +
mbilical cord, in which the arteries describe spiral coils around the vein. The
 +
•teries convey the impure blood to the placenta, where it is purified, after which
 +
is returned to the abdomen of the foetus by the umbilical vein. After birth,
 +
lere being no further use for the placental circulation, the umbilical cord is tied,
 +
id the child separated from the mother. The umbilical arteries become imperious, and each is converted into a fibrous cord. The obliteration, however, does
 +
it involve the first i-J inches of the vessel, which persists as the internal iliac
 +
rtery of the adult. Moreover, the proximal end of the fibrous cord representing
 +
ie obliterated umbilical remains pervious also, and being connected with the
 +
iterior division of the internal iliac, it furnishes the superior vesical artery or
 +
"teries. This pervious portion lies along the side of the pelvis beneath the
 +
eritoneum, where it is crossed by the vas deferens in the male and the ligatentum teres of the uterus in the female. The foetal umbilical artery gives off
 +
ie inferior gluteal, which is the primitive main artery of the lower limb, until
 +
ie external iliac, which becomes the femoral, is developed.
 +
 
 +
Branches.—These are subject to much variation. In normal
 +
ases they arise from the two terminal divisions, anterior and posterior,
 +
xne of them being parietal in their distribution, which will be indicated
 +
y the letter P, whilst others are visceral, which will be indicated by
 +
he letter V. The branches are as follows:
 +
 
 +
 
 +
 
 +
924
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Anterior Division.
 +
 
 +
 
 +
Visceral.
 +
 
 +
Umbilical (which gives
 +
off superior vesical).
 +
Inferior vesical.
 +
 
 +
Middle rectal.
 +
 
 +
 
 +
Parietal.
 +
 
 +
Obturator.
 +
 
 +
Internal pudendal.
 +
Inferior gluteal.
 +
 
 +
 
 +
Posterior Division
 +
 
 +
Parietal.
 +
 
 +
Uio-lumbar.
 +
Lateral sacral.
 +
Superior gluteal.
 +
 
 +
 
 +
In the female the inferior vesical artery may be replaced by t
 +
vaginal, or the vaginal may be an independent branch; the uteri
 +
artery is always a special branch.
 +
 
 +
 
 +
Lateral J
 +
Sacral \
 +
 
 +
 
 +
 
 +
„■ Left Common Iliac
 +
 
 +
 
 +
Anterior Superioi
 +
Iliac Spine
 +
 
 +
Internal Iliac
 +
 
 +
_- Ilio-lumbar
 +
 
 +
_Posterior Division
 +
 
 +
_External Iliac
 +
 
 +
Anterior Division
 +
 
 +
 
 +
c • rrp
 +
 
 +
Superior
 +
Gluteal
 +
 
 +
Inferior Gluteal
 +
 
 +
 
 +
Sacro-spinous ^
 +
 
 +
Ligament A
 +
 
 +
Sacro-tuberous'
 +
 
 +
Ligament
 +
 
 +
Internal Pudendal'
 +
 
 +
Inferior Rectal
 +
 
 +
 
 +
Umbilical
 +
- - - ' Inferior Vesical
 +
Deep Circumflex Iliac
 +
Inferior Epigastric
 +
 
 +
....Obturator Nerve
 +
 
 +
-Obturator Artery
 +
 
 +
Obturator Vein
 +
 
 +
.Obturator
 +
Membrane
 +
 
 +
....Symphysis Pubis
 +
 
 +
 
 +
Superficial Perineal ‘
 +
 
 +
Transverse Perineal
 +
 
 +
 
 +
Dorsal Artery of Penis
 +
Deep Artery of Penis
 +
 
 +
Artery of the Bulb
 +
 
 +
 
 +
^ IG - 543 -—The Left Internal Iliac Artery and its Branches.
 +
 
 +
 
 +
Anterior Division. — 1 he superior vesical artery (V) arises from th
 +
pervious portion of the fibrous cord which represents the fcetal umbilica
 +
artery, and at once breaks up into several twigs which frequently hav
 +
independent origins. They are distributed to the upper portion of th
 +
bladder, and anastomose with the vesical of the obturator, and th
 +
mfeiior vesical of the same side, and with the superior vesical of th
 +
opposite side. The superior vesical furnishes the following branches
 +
urachal to the medial umbilical ligament; ureteric to the lower end c
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
925
 +
 
 +
 
 +
L e ureter; and deferential (as a rule) to the vas deferens, though this
 +
•anch may arise from the inferior vesical. The artery to the vas deferens,
 +
tiich is usually of small size, divides into a descending and an ascendg branch. The descending branch passes downwards to supply the
 +
npulla of the vas deferens and the seminal vesicle. The ascending
 +
■anch accompanies the vas deferens through the deep inguinal ring
 +
id inguinal canal into the scrotum, supplying the vas deferens, and
 +
ving a few twigs to the tail of the epididymis, in which latter situation
 +
anastomoses with the epididymal branch of the testicular artery,
 +
i the spermatic cord it also anastomoses with the cremasteric branch
 +
the inferior epigastric. The artery to the vas is sometimes of large
 +
ze, and then takes the place of the testicular artery if that vessel
 +
Lould be absent. One of the branches of the superior vesical artery is
 +
unetimes spoken of as the middle vesical.
 +
 
 +
The inferior vesical artery (V) takes an inward course to the lower
 +
)rtion of the bladder, which it supplies, giving branches to the seminal
 +
isicle, ampulla of the vas deferens, and prostate gland, and in the
 +
male to the vagina. It sometimes gives off the artery to the vas
 +
derens, and it may give origin to an accessory pudendal. It anastooses with the superior vesical and middle rectal of its own side, and
 +
ith its fellow of the opposite side.
 +
 
 +
The middle rectal artery (middle hsemorrhoidal artery) (V) often
 +
'ises in common with the inferior vesical. It is distributed to the
 +
ctum, and gives branches to the seminal vesicle, ampulla of the vas
 +
derens, and prostate gland. The anastomoses which it establishes
 +
'e with the superior rectal of the inferior mesenteric, the inferior
 +
:ctal of the internal pudendal, the inferior vesical of its own side, and
 +
s fellow of the opposite side.
 +
 
 +
The obturator artery (P) passes along the outer wall of the pelvic
 +
ivity on its way to the obturator canal, lying between the parietal
 +
dvic fascia and the peritoneum. It has the obturator nerve above
 +
, and its own vein below it. In entering the obturator canal, by which
 +
emerges from the pelvis, the artery does not pierce the parietal pelvic
 +
; scia, but passes over its upper border, where that joins the upper part
 +
• the obturator membrane. As the artery passes along the pelvic wall
 +
furnishes the following branches: muscular to the obturator internus ;
 +
iac to the iliac fossa, which supplies the bone, psoas major, and iliacus,
 +
id anastomoses with the iliac branch of the ilio-lumbar; vesical, which
 +
caches the side of the bladder within the lateral false ligament; and
 +
ubic to the back of the body of the os pubis, where it anastomoses with
 +
ie pubic branch of the inferior epigastric from the external iliac, and
 +
s fellow of the opposite side.
 +
 
 +
For the distribution of the obturator artery outside the pelvis,
 +
P- 589
 +
The obturator artery sometimes arises from the inferior epigastric
 +
iee P. 566).
 +
 
 +
The internal pudendal artery (internal pudic artery) (P) is one of
 +
 
 +
ie terminal branches of the anterior division. It descends with the
 +
 
 +
 
 +
 
 +
926
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
inferior gluteal artery upon the pyriforrnis and sacral nerves, a
 +
emerges from the pelvis through the lower compartment of the grea
 +
sciatic foramen, having previously pierced the parietal pelvic fas(
 +
The intrapelvic branches of the vessel are unimportant, and are c
 +
tributed to the pyriforrnis, coccygeus, obturator internus, and pel
 +
fascia. For the further course and distribution of the artery, see 1
 +
gluteal region and the perineum, pp. 539 and 686.
 +
 
 +
The inferior gluteal artery (sciatic artery) (P) is the other and lap
 +
terminal branch of the anterior division. It descends, usually behi
 +
the internal pudendal, upon the pyriforrnis and sacral nerves, a
 +
emerges from the pelvis through the lower compartment of the grea
 +
sciatic foramen, having previously pierced the parietal pelvic fasc
 +
Within the pelvis the artery gives off branches to the pyriforrnis, levai
 +
ani, coccygeus, rectum, bladder, seminal vesicle, and prostate glar
 +
Although very variable in their origin and course, the inferior gluti
 +
artery as it runs backwards frequently passes between the anter:
 +
primary divisions of the first and second sacral nerves and the interi
 +
pudendal between those of the second and third sacral nerves.
 +
 
 +
For the extrapelvic course and distribution of the vessel, see p. 5'
 +
 
 +
Posterior Division. —The ilio-lumbar artery (P) passes upwards a:
 +
outwards in front of the sacro-iliac articulation, between the lurnt
 +
sacral trunk and obturator nerve. In its course it passes behind t
 +
external iliac, or, it may be, the common iliac, vessels, and also behi]
 +
the psoas major and iliacus. On reaching the back part of the ili
 +
fossa it divides into two branches, iliac and lumbar. The iliac brant
 +
passing transversely, ramifies in the iliacus and ilium, and anastomos
 +
with the iliac branch of the obturator and branches of the deep circui
 +
flex iliac from the external iliac. The lumbar branch ascends benea
 +
the psoas major on to the quadratus lumborum, where it anastomos
 +
with the terminal part of the deep circumflex iliac, and the last lumb
 +
of the abdominal aorta. In its course it furnishes a spinal branch, whi<
 +
enters the vertebral canal through the intervertebral foramen betwe^
 +
the fifth lumbar and first sacral vertebrae, to be distributed in a mann
 +
similar to the other spinal arteries.
 +
 
 +
The lateral sacral arteries (P) are usually two in number, superi
 +
and inferior. They course downwards and inwards to the front
 +
the lateral mass of the sacrum, passing in front of the pyriforrnis ar
 +
sacral nerves. Upon the sacrum both arteries lie lateral to the anterf
 +
sacral foramina, the superior being confined to the region of the fir
 +
two foramina, whilst the inferior descends as low as the coccyx, whe:
 +
it anastomoses with the median sacral artery. They are distributf
 +
to the pyriforrnis and sacral nerves, and furnish spinal branches, whic
 +
enter the anterior sacral foramina, and so reach the sacral canal, whe]
 +
they supply its contents. Each spinal branch, before entering tl
 +
sacral canal, gives off a posterior branch, which emerges through tl
 +
posterior sacral foramen, and anastomoses with branches of the superk
 +
and inferior gluteal and internal pudendal. The lateral sacral arterk
 +
anastomose with each other and with the median sacral.
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
927
 +
 
 +
 
 +
The superior gluteal artery (P) is a large vessel, which is the connation of the posterior division. It is destined for the supply of the
 +
iteal region, and lies within the pelvis for a very short distance. Its
 +
■ection is backwards through the parietal pelvic fascia, and between
 +
3 lumbo-sacral trunk and the anterior primary division of the first
 +
:ral nerve, its escape from the pelvis being through the upper comrtment of the greater sciatic fordfaten. The branches of the artery
 +
thin the pelvis are unimportant.
 +
 
 +
For the extrapelvic course and distribution of the vessel, see p. 536.
 +
The branches of the internal iliac, with one exception, have to
 +
irce the pelvic fascia. The exception is the obturator artery, which,
 +
stated, passes over the upper border of the parietal pelvic fascia at
 +
e obturator canal.
 +
 
 +
Internal Iliac Vein. —This vessel results from the union of tributaries
 +
lich correspond, for the most part, with branches of the internal
 +
ic artery. The ilio-lumbar vein, however, is an exception, inasmuch
 +
it is a tributary of the common iliac vein. Moreover, during foetal
 +
3 the umbilical vein, which corresponds to the umbilical artery, passes
 +
the liver after entering the abdomen of the foetus. The internal iliac
 +
in extends from the upper part of the greater sciatic notch to the
 +
:ro-iliac articulation on a level with the pelvic brim, where it joins
 +
e external iliac, and so the common iliac vein is formed. In its course
 +
lies behind the corresponding artery. There are no valves in the vein
 +
elf, but its branches are freely provided with them.
 +
 
 +
The internal iliac vein is developed from the lower part of the cardinal
 +
in.
 +
 
 +
Internal Iliac Lymphatic Glands. —These glands are about ten in
 +
mber, and are associated with the origins of the branches of the
 +
ternal iliac artery. They are arranged in a curve, which usually
 +
gins in front in a gland situated between the obliterated umbilical
 +
d obturator arteries, and then is formed in succession by uterine
 +
prostatic, inferior gluteal and internal pudendal, middle rectal,
 +
perior gluteal and sacral glands. They are situated immediately
 +
ider the peritoneum, between it and the parietal layer of pelvic fascia,
 +
though occasionally some of them may be formed lateral to this
 +
scia.
 +
 
 +
The afferent vessels of the internal iliac glands return lymph from
 +
e parts supplied by the branches of the internal iliac artery. Thus,
 +
ey receive afferent vessels from the following parts:
 +
 
 +
1. The anal canal, but not the anal margin.
 +
 
 +
2. Lower part of the rectum.
 +
 
 +
3- Bladder.
 +
 
 +
4- Seminal vesicle and vas deferens.
 +
 
 +
5 - Prostate gland.
 +
 
 +
6. Prostatic, membranous, and bulbar portions of the urethra,
 +
part.
 +
 
 +
7 - Uterus (cervix).
 +
 
 +
8. Vagina.
 +
 
 +
 
 +
928
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
9. Deep structures of gluteal region, supplied by superior glu
 +
artery.
 +
 
 +
10. Deep structures of upper part of back of thigh, supplied
 +
inferior gluteal artery.
 +
 
 +
11. Obturator region.
 +
 
 +
12. Deep structures of perineum.
 +
 
 +
The efferent vessels of the internal iliac glands pass to the mic
 +
group of common iliac glands.
 +
 
 +
Anterior Primary Divisions of the Sacral and Coccygeal Ner
 +
 
 +
—There are five sacral nerves and one coccygeal nerve on either s
 +
The anterior primary divisions of the first four sacral nerves enter
 +
 
 +
pelvis through the anterior sa<
 +
foramina, and that of the fifth sa<
 +
passes between the inferior lab
 +
angle of the sacrum and the trt
 +
verse process of the first coc
 +
geal vertebra, through the coccyg
 +
muscle. The anterior primary d
 +
sion of the coccygeal nerve enl
 +
the pelvis below the transverse j:
 +
cess of the first coccygeal verte
 +
through the coccygeus muscle. '
 +
first and second sacral nerves
 +
of large size, and their course
 +
obliquely downwards and outwai
 +
Beyond the second they dimin
 +
rapidly in size, and pass more h<
 +
zontally. They receive grey rz
 +
communicantes from the adjao
 +
ganglia of the pelvic sympathy
 +
trunk, and the third and fou]
 +
nerves (sometimes also the secoi
 +
furnish white rami communican
 +
to the corresponding pelvic plex
 +
The anterior primary divisions of 1
 +
first and second sacral nerves divi
 +
each into an anterior or ventral and a posterior or dorsal bran<
 +
dhe anterior primary division of the third sacral nerve divides ir
 +
an upper and a lower branch and is known as the nervus bigemin\
 +
The anterior primary division of the fourth sacral nerve also divic
 +
into an upper and a lower branch, and it is known as a nervus furcal
 +
The lumbo-sacral trunk in two divisions, ventral and dorsal, the anted
 +
primary divisions c>f the first two sacral nerves, the upper and low
 +
branches of the third sacral, and the small upper branch of the four
 +
sacral form the sacral plexus, whilst the large lower branch of the four
 +
sacral, the fifth sacral, and the coccygeal form the coccygeal plexus.
 +
 
 +
Sacral Plexus. —This plexus, formed as stated, is a large flatten
 +
mass, lying upon the pyriformis muscle, and behind the parietal pel\
 +
 
 +
 
 +
 
 +
 
 +
 
 +
Fig. 544.— Plan of Position of
 +
Structures lying on the Front
 +
of the Sacrum.
 +
 
 +
LSA, lateral sacral arteries; MSA,
 +
middle sacral arteries; C, coccygeal ganglion ; SS lig., sacrospinous ligament.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
929
 +
 
 +
 
 +
cia, which separates it from the inferior gluteal and pudendal vessels.
 +
3 mass ultimately forms two bands, upper and lower. The upper
 +
sciatic band, which is the larger of the two, receives the lumbo-sacral
 +
nk, first sacral, larger portion of the second sacral, and upper branch
 +
the third sacral nerves. It is flat and somewhat triangular, and is
 +
itinued into the sciatic nerve, whjch leaves the pelvis through the
 +
r er part of the greater sciatic foramen below the pyriformis without
 +
rcing the parietal pelvic fascia. The upper band and its contributory
 +
ves are sometimes spoken of as the sciatic plexus . The lower or
 +
 
 +
A
 +
 
 +
 
 +
 
 +
^ IG - 545-— A, The Sacral Plexus; B, The Sacro-Coccygeal Plexus.
 +
 
 +
A B
 +
 
 +
c > 1 , 1 . Nerve to Quadratus Femoris 4 .S. Fourth Sacral, giving a Branch to Sacral Plexus
 +
 
 +
l > 2 > 2 - Nerve to Obturator Internus V. Visceral Branches
 +
 
 +
b 3> 3- Posterior Cutaneous Nerve of Thigh M. Muscular Branches
 +
 
 +
T.C. Terminal Cutaneous Branches
 +
 
 +
 
 +
endal band, the smaller of the two, receives fibres from the second
 +
er branch of the third, and upper branch of the fourth sacral nerves,
 +
^ is continued into the pudendal nerve, which leaves the pelvis, like the
 +
tic, through the lower compartment of the greater sciatic foramen
 +
hout piercing the parietal pelvic fascia. The lower band and its
 +
tributory nerves are sometimes spoken of as the pudendal plexus.
 +
' sciatic and pudendal nerves are thus the terminal branches of the
 +
r al plexus. The reason of the name nervus bigeminus, as applied to
 +
third sacral nerve, is because it enters into the sciatic band by its
 +
)er branch, and into the pudendal band by its lower branch.
 +
 
 +
59
 +
 
 +
 
 +
 
 +
930
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Branches. —The branches of the sacral plexus are arranged in
 +
groups—collateral and terminal.
 +
 
 +
Collateral Group. —The branches of this group form three sel
 +
visceral, muscular, and cutaneous.
 +
 
 +
Visceral Branches. —These are derived from the third sacral
 +
that part of the fourth which enters into the sacral plexus (someti:
 +
also from the second). They are white rami communicantes, wl
 +
reinforce the pelvic plexus of the sympathetic, a few of them b(
 +
traceable independently to the pelvic viscera. They are known as
 +
pelvic splanchnics.
 +
 
 +
Muscular Branches .—The superior gluteal nerve arises by< tl
 +
roots from the dorsal divisions of the descending branch of the for
 +
lumbar, fifth lumbar, and first sacral nerves. It passes outwards
 +
backwards, and leaves the pelvis with the superior gluteal artery thro
 +
the upper compartment of the greater sciatic foramen, to be distribr
 +
to the gluteus medius, gluteus minimus, and tensor fasciae latae muse
 +
The inferior gluteal nerve arises by three roots from the do
 +
divisions of the fifth lumbar and first and second sacral nerves,
 +
leaves the pelvis through the lower compartment of the greater sci
 +
foramen, below the pyriformis and dorsal to the sciatic nerve, to
 +
distributed to the gluteus maximus. It is usually intimately associa
 +
with the posterior cutaneous nerve of thigh.
 +
 
 +
The nerves to the pyriformis, which are usually two in numl
 +
spring from the dorsal divisions of the first and second sacral nerve
 +
The nerve to the obturator internus and gemellus superior ar
 +
by three roots from the ventral divisions of the fifth lumbar and t
 +
and second sacral nerves. It leaves the pelvis through the lo
 +
compartment of the greater sciatic foramen, crosses the back of
 +
ischial spine, where it lies lateral to the internal pudendal vessels, ;
 +
then passes through the lesser sciatic foramen to the outer wall of
 +
ischio-rectal fossa, where it enters the inner or pelvic surface of
 +
obturator internus. In the gluteal region it gives a branch to
 +
gemellus superior when that muscle is present.
 +
 
 +
The nerve to the quadratus femoris and gemellus inferior arises
 +
three roots from the ventral divisions of the descending brand]
 +
the fourth lumbar, fifth lumbar, and first sacral nerves. It leaves
 +
pelvis through the lower compartment of the greater sciatic foran
 +
and then lies between the ischium and the sciatic nerve. It s
 +
sequently descends over the back of the capsular ligament of the 1
 +
joint, to which it usually gives a branch, and beneath the gemelli;
 +
obturator internus to the deep surface of the quadratus femoriSj
 +
which it ends, having previously given a branch of the gemellus infer
 +
Cutaneous Branches .—The posterior cutaneous nerve of thigh (sr
 +
sciatic nerve) arises by three roots from the posterior aspects of
 +
first, second, and third sacral nerves. It leaves the pelvis through
 +
lower compartment of the greater sciatic foramen, and is distribu
 +
to (i) the lower and outer part of the gluteal region by its glui
 +
cutaneous branches, (2) the skin of the scrotum by the long perir
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
93 i
 +
 
 +
 
 +
rve, (3) the skin of the back of the thigh, and (4) the skin of the back
 +
the leg as low as about the centre of the calf.
 +
 
 +
The perforating cutaneous nerve arises by two roots from the
 +
sterior aspects of the second and third sacral nerves. It passes
 +
ckwards through the sacro-tuberous ligament, after which it turns
 +
and the lower border of the glutefis maximus near the coccyx to be
 +
stributed to the skin over the lower and inner part of that muscle.
 +
Terminal Group. —This group is comprised of two nerves—namely,
 +
e sciatic and the pudendal.
 +
 
 +
The sciatic nerve is the continuation of the upper or sciatic band of
 +
e sacral plexus. In reality it is made up of the two divisions in which
 +
ultimately ends—namely, the lateral and medial popliteal—which lie
 +
>se together within the same sheath. Sometimes, however, these two
 +
visions arise separately from the sacral plexus, in which cases the
 +
:eral popliteal nerve may pass through the pyriformis. Again,
 +
ough the sciatic nerve may be apparently single, a careful dissection
 +
it, after the removal of its sheath, will reveal the lateral and medial
 +
pliteal nerves, which can be shown to have independent origins. The
 +
;eral popliteal nerve derives its fibres from the dorsal divisions of the
 +
scending branch of the fourth lumbar, fifth lumbar, and first and
 +
:ond sacral nerves; and the medial popliteal nerve derives its fibres
 +
>m the ventral divisions of the foregoing nerves, and in addition from
 +
e upper branch of the third sacral.
 +
 
 +
The sciatic nerve leaves the pelvis through the lower compartment
 +
the greater sciatic foramen below the pyriformis.
 +
 
 +
The pudendal nerve (pudic nerve) is the continuation of the lower
 +
pudendal band of the sacral plexus. It arises by three roots from
 +
e ventral division of the second, the lower branch of the third, and
 +
e upper branch of the fourth sacral, the root from the third being
 +
e largest. The nerve leaves the pelvis through the lower compartsnt of the greater sciatic foramen, crosses the back of the ischial
 +
ine, where it lies medial to the internal pudendal vessels, passes
 +
rough the lesser sciatic foramen, and then traverses the outer wall of
 +
e ischio-rectal fossa. Having given off the inferior haemorrhoidal
 +
rve, it divides into the perineal and dorsal nerve of penis, which
 +
th the internal pudic vessels are contained in the pudendal canal.
 +
 
 +
The sacral plexus and its branches being situated behind the parietal
 +
fvic fascia, the branches do not pierce the fascia as they leave the
 +
Ivis. The branches of the internal iliac artery, on the other hand,
 +
ing placed in front of the parietal pelvic fascia, have to pierce it,
 +
th the single exception of the obturator artery.
 +
 
 +
Coccygeal Plexus. —The nerves which form the plexus are the
 +
wer branch of the anterior primary division of the fourth sacral, the
 +
terior primary division of the fifth sacral, and the anterior primary
 +
vision of the coccygeal nerve. The upper branch of the fourth sacral
 +
ters the pudendal band of the sacral plexus, and the fourth sacral
 +
therefore a nervus fur calls, inasmuch as it gives a branch to the sacral
 +
exus and one to the coccygeal plexus. Before entering the coccygeal
 +
 
 +
 
 +
 
 +
932
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
plexus the lower branch of the fourth sacral nerves gives off visce:
 +
and muscular branches. The visceral branches for the most part re:
 +
force the pelvic plexus of the sympathetic as white rami commu:
 +
cantes, but a few of them pass independently to the pelvic visce:
 +
The muscular branches supply the levator ani, coccygeus, and sphincl
 +
ani externus. The branch to the latter muscle reaches the perinei
 +
either by piercing the coccygeus, or by passing between it and t
 +
levator ani, and besides supplying the external sphincter, it gi\
 +
branches to the skin between the coccyx and the anus. The nerve
 +
known as the perineal branch of the fourth sacral. The lower bran
 +
of the fourth sacral nerve, having parted with the foregoing offse
 +
descends upon the coccygeus, where it joins the fifth sacral, which h
 +
just entered the pelvis through that muscle. The conjoined nerve n<
 +
descends, and is soon reinforced by the coccygeal nerve, which a]
 +
enters the pelvis by piercing the coccygeus. In this manner t
 +
coccygeal plexus is formed. It lies at the lower part of the posted
 +
wall of the pelvis upon the coccygeus, and the nervous loop takes
 +
downward course. Subsequently it divides into several twigs, whi
 +
leave the pelvis by piercing the coccygeus, the sacro-spinous ligamei
 +
and the adjacent portion of the gluteus maximus to be distributed
 +
the skin over the coccyx.
 +
 
 +
Ureters. —The ureter of each side, having crossed the terminati
 +
of the common iliac, or the commencement of the external iliac artei
 +
enters the pelvis. It then passes downwards, describing a curve wi
 +
its convexity backwards and outwards, lying in front of the interr
 +
iliac artery. It next runs along the outer wall of the pelvis, lyi:
 +
beneath the peritoneum, and crossing medially the obturator vess<
 +
and nerve, and the obliterated umbilical artery. It subsequent
 +
passes inwards to the bladder, being crossed medially by the vas deferer
 +
Haying arrived at the lateral or ureteric angle of the bladder, it pass
 +
obliquely through the vesical wall anterior to the upper free end of t
 +
seminal vesicle, being here about 2 inches distant from its fellow, ai
 +
about 1 \ inches from the base of the prostate gland.
 +
 
 +
Bladder. —The bladder, when empty, or only moderately d:
 +
tended, lies entirely within the cavity of the pelvis. When, howeve
 +
it is fully distended, the apical part of the viscus rises above the le\
 +
of the symphysis pubis into the hypogastric region of the abdonn
 +
for at least 2 inches, and in cases of marked over-distension it may rea<
 +
to the umbilicus, or even higher. The bladder, therefore, has to 1
 +
considered under two aspects—namely, when empty or only moderate
 +
distended, and when fully distended.
 +
 
 +
The bladder, when empty or moderately distended , is triangular, ai
 +
presents the following component parts: an apex, a base, and a bod
 +
the latter presenting a superior surface, two inferior lateral surface
 +
two lateral borders, a posterior border, an antero-median border, ai
 +
two lateral angles.
 +
 
 +
The apex is directed forwards, and lies behind the upper part of t]
 +
symphysis pubis. It has connected with it the median umbilic
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
933
 +
 
 +
 
 +
lament representing the urachus , which ascends on the posterior
 +
rface of the anterior abdominal wall to the lower part of the umlicus. The base or fundus is directed backwards and downwards
 +
wards the rectum, from which it is separated by the seminal vesicles
 +
id terminal portions of the vasa deferentia, and the recto-vesical
 +
mina of the visceral portion of the pelvic fascia. The base is separated
 +
Dm the superior surface by the posterior border, and from each
 +
unded inferior lateral surface by a slight elevation, which extends
 +
Dm the lateral or ureteric angle of either side to the urethral opening,
 +
le superior surface is three-sided and slightly convex. It is usually
 +
lated to a few coils of the small intestine, and a loop or two of the
 +
lvic colon. The inferior lateral surfaces , which are convex, rest
 +
 
 +
 
 +
 
 +
d. 546.—Showing the Internal Trigone of the Bladder and the Relations of the Vas Deferens (DD), Ureter, etc., in its Neighbourhood.
 +
 
 +
'On (1) the symphysis pubis and the adjacent portions of the posterior
 +
rfaces of the bodies of the pubic bones, (2) the retro-pubic pad of
 +
“» ( 3 ) the medial pubo-prostatic ligaments, (4) the fasciae covering
 +
e u pper part of the obturator internus muscle and the upper surface
 +
the levator ani, and (5) the prostate gland. The lateral borders start
 +
)m the apex, whence they pass backwards in a diverging manner, and
 +
ch marks the separation between the superior surface and the correonding inferior lateral surface. Posteriorly each lateral border meets
 +
e posterior border. The posterior border extends transversely beeen the superior surface and the base. At either end it is joined by
 +
s lateral border. The lateral or ureteric angles are situated on either
 +
e at the junction of the lateral with the posterior border. At these
 +
gles the ureters pass through the vesical wall (Fig. 546). At its
 +
 
 +
 
 +
 
 +
934
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
most dependent point the bladder is continuous with the uretl
 +
There is, however, no contraction of the bladder at or near this poi
 +
in other words, no neck.
 +
 
 +
The external trigone is the name given to a limited triangular sp
 +
upon the exterior of the base, which is bounded as follows: above,
 +
the bottom of the recto-vesical pouch of peritoneum; laterally, by
 +
ampulla of the vas deferens, lateral to which is the seminal vesic
 +
and below, by the approximation of the ejaculatory ducts at the b
 +
of the prostate gland. The length of the space from the apex be]
 +
to the base above is, as a rule, fully i inch, but its breadth is limi
 +
by the encroachment upon it of the ampullae of the vasa deferen
 +
There is no peritoneum over this region.
 +
 
 +
The Bladder during Distension and when fully distended. —As
 +
bladder becomes distended very little alteration takes place in a doi,
 +
 
 +
ward direction. The
 +
 
 +
 
 +
Left Ureter
 +
 
 +
 
 +
Line of
 +
 
 +
Reflection of-'
 +
Peritoneum
 +
 
 +
 
 +
External Trigone''
 +
 
 +
 
 +
 
 +
Ejaculatory Duct
 +
of Right Side
 +
 
 +
 
 +
THE
 +
 
 +
 
 +
marcations between i
 +
component parts of i
 +
viscus gradually disappe
 +
and it becomes ovoid. 1
 +
apex appears above 1
 +
symphysis pubis, and
 +
the organ increases in s
 +
the apex and the super
 +
portion of the body asce
 +
into the hypogastrium
 +
such a manner as to st:
 +
off the parietal peritonei
 +
from the back of the lin
 +
alba. In this way a p<
 +
tion of the original inferi
 +
lateral surface, devoid
 +
 
 +
 
 +
Fig. 547. —Dissection of the Base of . . , , .
 +
 
 +
Bladder, showing the Seminal Vesicles, peritoneum, is brought in
 +
Vasa Deferentia, and External Trigone, direct contact with t
 +
 
 +
back of the linea all
 +
which is now also free from peritoneal covering. A distended bladd
 +
may therefore be punctured or opened through the linea alba abo
 +
the symphysis pubis without doing any injury to the peritoneui
 +
The bladder is now becoming spheroidal, and its long axis is direct
 +
downwards and backwards. The part which rises highest is not t
 +
original urachal apex, but that part of the superior surface which
 +
immediately adjacent to, and behind, the apex.
 +
 
 +
Peritoneal Relations. —The only part of the bladder which is coven
 +
by peritoneum is the superior surface. The peritoneum is reflect!
 +
from the apex along the urachus, and at either side it leaves the org;
 +
along the lateral border. When the bladder is distended the latei
 +
reflection of peritoneum appears to take place along the course of t;
 +
obliterated umbilical artery, but this is due to the lateral distensh
 +
and elevation of the viscus, the obliterated umbilical itself lying aloi
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
935
 +
 
 +
 
 +
outer wall of the pelvis. For the structure and development of
 +
bladder, see pp. 949 and 955.
 +
 
 +
Vas Deferens in the Pelvis. —The vas deferens enters the abdomen
 +
)ugh the deep inguinal ring, where it lies on the inner side of the
 +
er constituents of the spermatic cord.- It then hooks round the
 +
er side of the inferior epigastric artery, and having crossed the
 +
ernal iliac vessels from without inwards, it dips down on the inner
 +
; of the external iliac vein. In this way it enters the pelvis under
 +
er of the peritoneum. It now passes backwards and downwards
 +
>n the lateral wall, crossing median to the obliterated umbilical
 +
ery, the ureter, and the obturator vessels and nerve. It is then
 +
 
 +
Symph. Pub.
 +
 
 +
 
 +
 
 +
Fig. 548. —Transverse Section through Last Piece of Sacrum
 +
 
 +
(after Symington).
 +
 
 +
 
 +
ected inwards to the inner aspect of the upper end of the seminal
 +
side, whence it passes downwards, inwards, and forwards along the
 +
se of the bladder, where it lies close to the inner side of the seminal
 +
side. This part of the vas deferens, which comes very near its fellow,
 +
lilated and sacculated, like the adjacent seminal vesicle, and is known
 +
the ampulla. Close to the base of the prostate gland the sacculans disappear, and the duct, having become very narrow, is joined
 +
the outer side at an acute angle by the duct of the seminal vesicle, and
 +
the ejaculatory duct is formed, which will be presently described.
 +
t the structure and development of the vas deferens, see pp. 737
 +
d 753
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
936
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
Seminal Vesicles. —These are two in number, right and left, and
 +
between the base of the bladder and the rectum. They are sacculat
 +
reservoirs for the seminal fluid, and each is conical, being about 2 incl
 +
long, and about J inch broad at the widest part. The broad end
 +
free, and looks upwards, outwards, and backwards. It is covei
 +
posteriorly in its upper part by the peritoneum, which forms the rec
 +
vesical pouch, while anterior to it is the ureter as that is about to p;
 +
through the bladder. The upper ends of the two seminal vesicles ;
 +
wide apart, and the bottom of the recto-vesical pouch descends betwf
 +
 
 +
 
 +
 
 +
AnalCanal
 +
 
 +
Bulb of Corp.
 +
 
 +
Spong.
 +
 
 +
 
 +
Ureter
 +
 
 +
 
 +
V. Def.
 +
Bladder
 +
 
 +
 
 +
Prostate
 +
 
 +
 
 +
Fig. 549.—Median Sagittal Section through Male Pelvis.
 +
 
 +
 
 +
them for a short distance. The lower end of each, which is nari
 +
and free from sacculations, approaches its fellow, the vasa deferer
 +
intervening. This lower end represents the duct, which, as stat
 +
joins the vas deferens at an acute angle close to the base of the prost
 +
gland, and so gives rise to the ejaculatory duct. For the struct
 +
and development of the seminal vesicles, see p. 958.
 +
 
 +
Ejaculatory Ducts. —These are two in number, right and left. E«
 +
is formed by the union of the duct of the seminal vesicle with the
 +
deferens close to the base of the prostate gland; it is about 1 inch
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
937
 +
 
 +
 
 +
ngth. The two ducts pass downwards, forwards, and inwards through
 +
e prostate gland between the middle and lateral lobes, and each enters
 +
e lateral wall of the prostatic utricle to terminate in a minute aperture
 +
i the lateral margin of the opening of the prostatic utricle. For the
 +
ructure and development of the ejaculatory ducts, see p. 955.
 +
Prostate Gland. —This gland surrounds the first ij inches of the
 +
ethra. It is firm in consistence, and in shape and colour resembles
 +
chestnut—that is to say, it is conical and of a reddish-brown colour,
 +
is subject to much variety in size, but its average measurements
 +
ay be stated as follows: the transverse diameter at the base is about
 +
inches; the vertical diameter from base to apex is about ij inches;
 +
 
 +
 
 +
Sperm. Cord Corp. Cavern.
 +
 
 +
 
 +
 
 +
t \
 +
 
 +
/ \ >
 +
 
 +
Coccyx Rectum
 +
 
 +
 
 +
Fig. 550 -—Transverse Section at Level of Coccyx (after Symington).
 +
 
 +
id the antero-posterior diameter is about f inch. The average weight
 +
: the organ is about \\ drachms.
 +
 
 +
The gland is situated fully ij inches from the anus, and its anterior
 +
irface is about f inch below and behind the lower part of the symphysis
 +
ubis. It presents a base, an apex, a posterior or rectal surface, an
 +
iterior or pubic surface, and two lateral surfaces. The base, which
 +
directed upwards, surrounds the urethra, and is intimately connected
 +
ith the vesical wall. Notwithstanding this, however, there is a supernal line of demarcation between the two, which takes the form of an
 +
mular groove, occupied by a portion of the prostatic venous plexus,
 +
be ejaculatory ducts enter the base close to the upper part of the
 +
asterior or rectal surface, where there is a small transverse cleft
 +
died the prostatic fissure. The apex is directed downwards, and is
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
938
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
the most dependent part of the organ. It is in contact with the super
 +
layer of the perineal membrane. The posterior or rectal surface is f
 +
and triangular. It is directed backwards and slightly downwar
 +
and is set upon the anterior wall of the rectum, from which it is separal
 +
by the recto-prostatic lamina of the visceral portion of the pelvic fast
 +
This surface is accessible to manipulation on introducing the finger ir
 +
the anal canal, and carrying it up for fully ij inches. The anterior
 +
pubic surface, which is convex, is so much projected as to be really
 +
anterior round border which separates the two lateral surfaces. Itl
 +
about § inch behind the lower part of the symphysis pubis, from wh:
 +
it is separated by a portion of the prostatic venous plexus, the ret
 +
pubic pad of fat, and the medial pubo-prostatic ligaments. 1
 +
anterior surface projects between the anterior borders of the levato
 +
ani muscles. The lateral surfaces are convex, and stand out in 1
 +
relief. Each is embraced by the anterior fibres of the correspond]
 +
levator ani, which constitute the so-called levator prostatae muse
 +
When an accessory pudendal artery is present it passes over the late
 +
surface, and might be endangered in lateral lithotomy.
 +
 
 +
The gland is usually regarded as composed of three lobes, t 1
 +
lateral and a middle, but, though the middle lobe can usually
 +
demarcated without much difficulty, there is no external indicati
 +
of any separation between the lateral lobes. The lateral lobes foi
 +
the chief bulk of the gland, and they meet and become continuous
 +
front of and behind the prostatic portion of the urethra, forming t
 +
anterior and posterior commissures. The middle lobe represents tl
 +
part of the basal portion of the gland which is wedged in between t
 +
ejaculatory ducts and prostatic utricle behind and the urethra in fra
 +
and which lies just below the apex of the trigonum vesicse. It is i:
 +
portant to note that the middle lobe lies behind the commencement
 +
the urethra. It is liable to become hypertrophied in old age, and m
 +
then produce undue elevation of the uvula vesicae in the interior of t
 +
bladder, which is a natural product of it. In this manner, by blocki
 +
the internal orifice of urethra, it may not only give rise to difficulty
 +
micturition, but may also obstruct catheterization.
 +
 
 +
The prostate gland is traversed by the first i J inches of the ureth:
 +
The ejaculatory ducts are also contained within the gland, in which th
 +
pass downwards and inwards between the middle and lateral lob'
 +
For the structure and development of the prostate gland, see pp. 9
 +
and 960.
 +
 
 +
Urethra. —The male urethra commences at the internal orifice
 +
urethra of the bladder, and terminates at the extremity of the gla
 +
penis in a vertical fissure, called the external orifice of urethra. It
 +
about 8 inches in length, and is divided into three portions, whit
 +
from the bladder outwards, are called prostatic, membranous, a
 +
spongy. The prostatic and membranous portions constitute t
 +
non-penile part of the canal, and the spongy portion, being contain
 +
within the corpus spongiosum of the penis, represents the per
 +
part.
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
939
 +
 
 +
 
 +
rhe prostatic portion of the urethra is the part of the canal which
 +
ontained within the prostate gland. It is inches in length,
 +
its course is almost vertical, there being a slight curve with the
 +
:avity directed forwards. It is spindle-shaped, being wider at the
 +
;re than at either end, and at its upper or vesical end it is rather
 +
sr than at the lower end. Its diameter at the centre, which is the
 +
est part of the entire canal, is rather more than ^ inch; at the upper
 +
r esical end it is rather less than this, and at the lower end it is still
 +
. This portion of the urethra, though surrounded by the -prostate
 +
id, is the most dilatable part of the whole canal. Close to the
 +
Ider, however, it usually offers some resistance to the passage of an
 +
rument. Its walls are anterior and posterior, the latter being often
 +
ken of as the floor. These walls are in contact with each other,
 +
spt during the passage of fluid, and the mucous membrane is thrown
 +
) longitudinal folds. The posterior wall presents along the middle
 +
 
 +
 
 +
Median Umbilical Ligament
 +
 
 +
 
 +
 
 +
ig. 551.—Section of the Bladder and Penis to show the Urethra.
 +
 
 +
i a prominent narrow elevation of the mucous membrane, called the
 +
thral crest (verumontanum). It is about f inch long, and comnces either a little below the urethral orifice of the bladder or at the
 +
r er end of the uvula vesicas. As it descends it gradually becomes
 +
re prominent, assuming a height of about J inch, and then rapidly
 +
>sides. It is due to a thickening of the submucous tissue, which
 +
lses an elevation of the mucous membrane. On account of this protion a transverse section of this portion of the urethra is curved or
 +
scentic, with the convexity directed forwards. On either side of the
 +
st there is a longitudinal groove, called the prostatic sinus, into which
 +
^ majority of the prostatic ducts open. A few of these ducts, howT from the middle lobe open in the median line above the crest, or,
 +
he crest commences at the lower end of the uvula vesicae, upon its
 +
per part. Immediately below the most prominent part of the crest
 +
*e is the opening of a small blind recess, called the prostatic utricle
 +
 
 +
 
 +
 
 +
 
 +
 
 +
94°
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
(sinus pocularis). Its direction is upwards and backwards behind t'
 +
middle lobe of the prostate, and it is from £ to J inch in length. It
 +
somewhat flask-shaped, being narrow at its urethral orifice, but e
 +
panded at its deep csecal end. It may extend beyond the prostate ai
 +
is sometimes bifid. Upon the lateral margins of its orifice are the minu
 +
openings of the ejaculatory ducts. The utricle represents the uter
 +
and vagina in the female, being developed from the fusion of the posted
 +
or caudal ends of the para-mesonephric ducts.
 +
 
 +
When the middle lobe of the prostate becomes hypertrophied
 +
blocks the urethral orifice of the bladder, as has been stated, by press!
 +
the uvula vesicae over it from behind, and so gives rise to difficulty
 +
micturition, and obstructs catheterization. When both lateral lob
 +
become uniformly hypertrophied, the prostatic portion of the ureth
 +
undergoes increase in length. When only one lateral lobe is involv
 +
in the hypertrophy it presses against the urethra, and, producing d
 +
tortion of the canal, gives rise to difficulty in micturition, and oft
 +
considerable obstruction in catheterization.
 +
 
 +
Structure. —The mucous membrane of the prostatic urethra
 +
surrounded externally by the inner circular muscular fibres of t
 +
prostate, and is covered internally by transitional epithelium.
 +
 
 +
The membranous portion of the urethra si;cceeds to the prostai
 +
portion, and extends from the apex of the prostate gland to the coi
 +
mencement of the spongy portion. It is contained, for the most pa:
 +
between the two layers of the perineal membrane, but it also exten
 +
for a short distance (J inch) beyond the inferior layer of that structm
 +
It is the shortest and narrowest part of the canal, with the except!
 +
of the external orifice of urethra. Its length is £ inch along the anteri
 +
wall, and J inch along the posterior, the difference being due to t
 +
fact that the membranous urethra passes into the spongy part in
 +
slanting manner at a point £ inch in front of the posterior extremi
 +
of the bulb. The back part of the bulb projects backwards for £ in
 +
over the posterior wall of the membranous urethra, and is here lyi
 +
in front of the inferior layer of the perineal membrane. It is in tl
 +
situation where a false passage is liable to be made in catheterizatic
 +
partly because the walls are here very thin, and partly by reason
 +
the backward extension of the posterior extremity of the bulb. T.
 +
diameter of the membranous urethra is £ inch. It lies about i m
 +
behind and below the inferior ligament of symphysis pubis, and ]
 +
direction is downwards and slightly forwards. It describes a geni
 +
curve, the concavity of which looks forwards and upwards towards t
 +
lower part of the symphysis pubis. As the membranous urethra pass
 +
through the superior layer of the perineal membrane, which is form
 +
by the parietal pelvic fascia, the fascia is prolonged upwards to foi
 +
part of the capsule of the prostate gland. Moreover, as it pierces t
 +
inferior layer of the perineal membrane about i inch below the syi
 +
physis pubis, it carries with it a prolongation from the margins of t
 +
urethral opening, which forms a fascial investment for the bulb, h
 +
tween the two layers of the perineal membrane the membranous ureth
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
94 1
 +
 
 +
 
 +
irrounded by the fibres of the sphincter urethrae muscle, and the
 +
o-urethral glands lie behind it, one on either side of the middle
 +
 
 +
 
 +
Structure. —External to the mucous membrane there is a layer of
 +
tile tissue, and outside this there is a layer of circularly-disposed
 +
1 muscular fibres,
 +
 
 +
:h are continuous I "* e ™ laic: vesic*
 +
 
 +
/e with the circular Bell’s Muscle I ; Left Ureteric Opening
 +
 
 +
cular fibres of the
 +
itate around the proic urethra. External
 +
his, again, there are
 +
sphincter fibres of
 +
sphincter urethrae,
 +
mucous membrane is
 +
ned by columnar epium. The membranportion of the urethra
 +
ransverse section pre:s the appearance of
 +
ircular opening, the
 +
len of which is
 +
iched, this being due
 +
the longitudinal folds
 +
• which the mucous
 +
nbrane is thrown.
 +
 
 +
The spongy portion of
 +
urethra succeeds to
 +
membranous portion,
 +
is contained within
 +
corpus spongiosum of
 +
penis, and extends
 +
n a point \ inch in
 +
it of the posterior exility of the bulb and
 +
the inferior layer of
 +
perineal membrane
 +
the external orifice of
 +
thra on the extremity
 +
the glans penis. It is
 +
 
 +
nit 6 inches in length, External Orifice of Urethra
 +
 
 +
1 its calibre is unequal Fig
 +
oughout. It presents
 +
i dilatations, one situated in the bulb, the intrabulbar fossa (which
 +
•resents about the first ij inches of the corpus spongiosum), and
 +
; other in the glans penis, the latter being called the terminal
 +
sa (fossa navicularis). The intrabulbar fossa is about ij inches in
 +
gth, whilst the terminal fossa is about J inch long. The diameter
 +
 
 +
 
 +
 
 +
-Crest
 +
 
 +
-Opening of Utricle
 +
 
 +
Prostate Gland in Section (showing Prostatic Portion of Urethra)
 +
 
 +
 
 +
-Membranous Portion of Urethra
 +
 
 +
Bulbo-urethral Gland of Left Side
 +
 
 +
 
 +
Left Half of Bulb of Urethra
 +
 
 +
Left Crus Penis
 +
 
 +
Openings of Ducts of Bulbourethral Glands
 +
 
 +
 
 +
-Spongy Portion of Urethra
 +
 
 +
 
 +
- [-Left Corpus Cavernosum
 +
 
 +
-Urethral Glands and Lacunas
 +
 
 +
Urethrales
 +
 
 +
 
 +
-Terminal Fossa
 +
 
 +
-Left Half of Glans Penis
 +
 
 +
 
 +
-The Interior of the Male Urethra.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
94 2
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
of that part of the spongy urethra which intervenes between the in
 +
bulbar fossa and the terminal fossa is about J inch. At the extei
 +
orifice of urethra the calibre of the canal is diminished, this being
 +
narrowest part of the entire canal. The spongy portion at its o
 +
mencement is directed forwards for a short distance, and then be
 +
downwards. It thus describes a curve, which is situated about 2 inc
 +
from its commencement, the concavity being directed downwa:
 +
This curve is fixed, and corresponds with the angle of the penis, the sit
 +
tion of which is immediately in front of the penile attachment of
 +
suspensory ligament, where drooping of the organ takes place,
 +
walls of the spongy part of the urethra are in contact, except dui
 +
the passage of fluid. A transverse section of it, except in the gk
 +
presents a transverse slit with anterior and posterior lips. In the gk
 +
however, the slit is vertical with its lips laterally disposed. At
 +
upper end of the terminal fossa—that is, the end most remote from
 +
external orifice of urethra-—the vertical slit is modified by the addil
 +
of a short transverse slit, and so presents the shape of an inverted
 +
as follows, J_.
 +
 
 +
Structure. —The mucous membrane of the spongy portion is j
 +
vided with elastic tissue, and is very vascular. It is covered
 +
columnar epithelium , except in the glans, where it is of the strati
 +
squamous variety. Outside the mucous membrane is the subrnuc
 +
coat, which contains two layers of plain muscular tissue—inner loi
 +
tudinal and outer circular. External to the submucous coat ther
 +
a plexus of veins, which forms part of the corpus spongiosum. '
 +
mucous membrane contains both simple and compound mucous glar
 +
called the urethral glands (glands of Littre), the openings of the dr
 +
of which are studded over the surface. In addition to these there
 +
other openings, which lead into small blind recesses, called the lacr
 +
urethrales, these openings being directed forwards. One lacuna,
 +
large size, called the lacuna magna, is situated on the roof of the fc
 +
navicularis about 1 inch from the meatus urinarius. The muc
 +
membrane which surrounds this lacuna is known as the valvule
 +
Guerin. Besides the foregoing openings, the ducts of the bul
 +
urethral glands open upon the floor of the bulbous portion of the uret.
 +
about 1 inch in front of the inferior layer of the perineal membrane.
 +
 
 +
There is sometimes a congenital deficiency in the floor of the spoi
 +
urethra, constituting the condition known as hypospadias. In ot
 +
cases the deficiency may be on the roof, and it is then known
 +
epispadias.
 +
 
 +
Lymphatics of the Male Urethra—Spongy Portion. —The lymphs
 +
vessels of the spongy portion communicate with those of the glans £
 +
with the deep lymphatics of the penis, and in part through this conn
 +
tion drain to the deep inguinal and external iliac glands. Much of'
 +
lymph, however, from this region drains into vessels which, accc
 +
panying first the vessels of the bulb and later the internal pudic vess<
 +
finally pass to the gland or glands of the internal iliac chain , which
 +
situated near the origin of the internal pudendal artery.
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
943
 +
 
 +
 
 +
ulbar and Membranous Portions. —The lymphatics of these portions
 +
to (i) the internal iliac glands, and (2) the inner chain of the external
 +
glands.
 +
 
 +
rostatic Portion. —The lymphatics of this portion join those of the
 +
;ance of the prostate gland, and pass to (1) the middle chain of
 +
xternal iliac glands, (2) the internal iliac glands, (3) the lateral
 +
l glands, and (4) the inner group of the common iliac glands.
 +
elvic Colon. —The pelvic colon succeeds to the iliac colon. It
 +
nences at the inner border of the left psoas major just anterior to
 +
jft sacro-iliac articulation, and terminates in front of the third sacral
 +
ibra, where it becomes continuous with the rectum. It is very
 +
ible in length, but measures on an average about 15 inches, and
 +
lly lies in the pelvic cavity, resting upon the bladder and rectum,
 +
ascending on either side of these viscera. It is surrounded by peri11m, which forms behind it an expanded wavy mesentery, called the
 +
0 meso-colon, which contains between its two layers the branches
 +
ie lower left colic arteries and the superior rectal artery, with the
 +
jsponding veins. The root of this mesentery is composed of two
 +
3, which become continuous at an acute angle. One limb takes an
 +
ird course along the inner border of the psoas major, and the other
 +
ss downwards over the sacral promontory to be attached to the
 +
rior surfaces of the first three sacral vertebrae. At its extremities,
 +
h are near each other, the mesentery is short, and the extremities of
 +
pelvic colon are necessarily fixed. The intervening portion, how, is long, and so allows of considerable mobility on the part of the
 +
ter portion of the attached gut. A very common course for the
 +
ic colon to take is to pass from the left wall to the right wall of the
 +
is, resting upon the bladder or uterus, then to pass backwards
 +
wing the posterior wall of the pelvic cavity until it arrives at the
 +
lie line, when it turns vertically downwards. A portion of it is
 +
itimes met with in the abdominal cavity.
 +
 
 +
tructure. —The chief difference in the structure of the pelvic colon,
 +
impared with the other divisions of the colon, affects the arranget of the longitudinal muscular fibres. Though arranged at first
 +
iree taeniae, these gradually become disposed as two broad taeniae,
 +
rior and posterior. When this has taken place, the longitudinal
 +
s almost surround the gut, except along the sides, in which situa3 the usual sacculations are formed. Appendices epiploicae are met
 +
over the pelvic colon.
 +
 
 +
Wood-supply. —The pelvic colon receives its arteries from the lower
 +
colic arteries, which are branches of the inferior mesenteric. The
 +
s pass to the inferior mesenteric vein, and ultimately into the
 +
al vein.
 +
 
 +
die lymphatics pass to the left lower pre-aortic glands.
 +
 
 +
die nerves are derived from the inferior mesenteric sympathetic
 +
 
 +
us.
 +
 
 +
tectum. —The rectum succeeds to the pelvic colon, and extends
 +
1 the front of the third sacral vertebra to a point 1J inches in front of
 +
 
 +
 
 +
944
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
and below the tip of the coccyx, where it pierces the pelvic diaphra^
 +
and terminates in the anal canal. Its direction is at first downwa
 +
and slightly backwards, then vertically downwards, and finally doi
 +
wards and forwards. It is fully 5 inches in length, and its diameter
 +
the most part is about ij inches in the empty state, but it becor
 +
enlarged above the anal canal, this dilated part being called the ampi
 +
recti. When empty, its anterior and posterior walls are in contact, c
 +
in transverse section it appears as a transverse slit. The rectun
 +
destitute of a mesentery. The peritoneum covers the upper th
 +
laterally and anteriorly , but not posteriorly, the middle third be
 +
covered by peritoneum only anteriorly , whilst the lower third is f
 +
from serous covering. The level at which the peritoneum leaves 1
 +
anterior surface of the rectum is usually about 3 inches above the an
 +
opposite the body of the fifth sacral vertebra.
 +
 
 +
The rectum, so far from being straight in man, presents both ante
 +
posterior and lateral curvatures. The antero-posterior flexures ;
 +
two in number, upper and lower. The upper curve extends from 1
 +
third sacral vertebra to the posterior or rectal surface of the prost;
 +
gland, and its concavity is directed forwards. The lower curve, wh]
 +
is abrupt, corresponds with the rectal surface of the prostate, its c(
 +
cavity looking backwards, and containing the ano-coccygeal body. T
 +
lateral flexures are of importance, because they tend to obstruct t
 +
passage of instruments by giving rise to the rectal valves (Housto
 +
These flexures are usually three in number—upper, middle, and low
 +
The upper and lower flexures have their convexities directed towai
 +
the right, whilst the middle flexure has its convexity directed towai
 +
the left. In the concavities of these flexures the rectal wall becoir
 +
inflected, and so gives rise to more or less prominent shelves of mucc
 +
membrane, which are known as the rectal valves. The lateral infk
 +
tions and resultant valves are associated with the erect posture of rm
 +
which posture throws considerable pressure upon the anal aperture ai
 +
its sphincter muscles. They are best marked in the distended recta
 +
and the lateral flexures are brought about in the following manner: T
 +
longitudinal muscular fibres of the rectum are rather shorter than t
 +
gut to which they are applied. Moreover, they are principally dispos'
 +
in two stout broad sheets, one on the anterior and the other on t.
 +
posterior wall, there being very few longitudinal fibres along the latei
 +
walls. The shortness of these longitudinal fibres therefore throws tl
 +
rectum into lateral flexures on account of the sparseness of the lon£
 +
tudinal fibres at the sides. These lateral flexures may be taken
 +
representing the sacculations of the other parts of the colon.
 +
 
 +
Relations— Anterior. —The recto-vesical pouch of peritoneum f (
 +
a short distance, usually containing coils of small intestine or of pelv
 +
colon; the base of the bladder, seminal vesicles, and vasa deferentia, wf
 +
the intervention of the recto-vesical lamina of the visceral pelvic fasci;
 +
and the posterior or rectal surface of the prostate gland, with the inte
 +
vention of the recto-prostatic lamina of the visceral pelvic fascia. J
 +
the female the anterior relations are (1) the recto-uterine pouch
 +
 
 +
 
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
945
 +
 
 +
 
 +
ritoneum (pouch of Douglas), with a few coils of small intestine or
 +
dvic colon, in front of which are the posterior surface of the body of
 +
e uterus and the upper part of the posterior wall of the vagina; and
 +
) the greater portion of the posterior wall of the vagina. Posterior .—
 +
le lower three sacral vertebrae, coccyx, levatores ani, and ano-coccygeal
 +
idy; the median and lateral sacral vessels, sacral lymphatic glands,
 +
cral nerves, and sacral sympathetic trunk. Behind the rectum there
 +
a large amount of areolar tissue. Lateral .—The pelvic sympathetic
 +
sxuses, levatores ani, and coccygei muscles, the lateral divisions of
 +
e superior rectal artery, and the corresponding veins.
 +
 
 +
Anal Canal. —This is the terminal portion of the large intestine,
 +
extends from the lower end of the rectum, where that has pierced
 +
e pelvic diaphragm at a point correonding to the apex of the prostate
 +
md, to the anus, and it is the part
 +
rich is surrounded by the sphincter
 +
uscles. It is about i-| inches in
 +
igth, and its lateral walls are in
 +
ntact, so that in transverse section
 +
appears as an antero-posterior slit,
 +
which respect it differs from the
 +
ctum proper. Its direction is downirds and backwards, and its antero(sterior diameter is from \ to f inch.
 +
 
 +
Relations. — Anterior. —The bulb of
 +
e penis, the base of the perineal
 +
smbrane, and the membranous part
 +
the urethra. In the female the
 +
rineal body is anterior to it, and
 +
parates it from the lower end of
 +
e vagina. Posterior .—The ano-coccyal body. Lateral .—The fat of the
 +
ririo-rectal fossae. The anal canal is
 +
)sely guarded by muscles in the folding manner and to the following
 +
tent: most internally is the sphincter
 +
 
 +
i internus continuous with the circular muscular fibres of the rest
 +
the gut; outside this are the longitudinal muscular fibres markedly
 +
enforced by the fibres of the levator ani, which here run longidinally; and most externally is the sphincter ani externus. For
 +
e structure and development of the rectum and anal canal, see
 +
960.
 +
 
 +
 
 +
 
 +
Fig. 553.—Diagram of Structure of Rectum and Anal
 +
Canal.
 +
 
 +
L, C, longitudinal and circular
 +
fibres of wall; the circular
 +
fibres thicken below to form
 +
the internal sphincter (IS) ;
 +
ES, external sphincter; LA,
 +
levator ani.
 +
 
 +
 
 +
Parts felt per Rectum in Catheterization. —A catheter having been passed
 +
k) the bladder, the following parts, in order from before backwards, may be
 +
t through the anterior wall of the bowel on the introduction of the index
 +
S er: (1) the membranous portion of the urethra; (2) the posterior or rectal
 +
rface of the prostate gland; and (3) the apical part of the external trigone of
 +
3 bladder, destitute of peritoneum, with a vas deferens on either side, and very
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
 
 +
946
 +
 
 +
 
 +
A MANUAL OF ANATOMY
 +
 
 +
 
 +
near each other—indeed, almost touching. During this examination the fin
 +
may come in contact with the lower left, and perhaps the right horizontal folc
 +
rectum.
 +
 
 +
Median Sacral Artery. —This vessel arises from the posterior asp
 +
of the abdominal aorta just above the bifurcation. Its course
 +
downwards in the middle line, behind the left common iliac vein a
 +
the hypogastric sympathetic plexus, and it rests in succession uj
 +
the following parts: the lower half of the body of the fourth luml
 +
vertebra and the disc between it and the fifth, the body of the fr
 +
lumbar and the disc between it and the first sacral vertebra, and 1
 +
pelvic surfaces of the sacrum and coccyx. In the pelvis it lies wit]
 +
the root of the pelvic meso-colon, being covered by a portion of i
 +
pelvic colon, as low as the third sacral vertebra, and beyond that il
 +
placed behind the rectum. On reaching the tip of the coccyx
 +
terminates in the coccygeal body. The branches of the artery are
 +
follows: anterior or rectal to the posterior wall of the rectum, where tl
 +
anastomose with the superior and middle rectal arteries; lateral to i
 +
front of the sacrum and coccyx, which anastomose with the late
 +
sacral arteries; and terminal to the coccygeal gland. The vessel usua
 +
furnishes a fifth pair of lumbar arteries, which wind round the sides
 +
the body of the fifth lumbar vertebra.
 +
 
 +
The median sacral artery represents the caudal aorta of anima
 +
and its lateral branches are serially homologous with the lumt
 +
branches of the abdominal aorta.
 +
 
 +
The median sacral vein is at first arranged as two venae comiti
 +
but these subsequently unite to form a single vessel, which usuaj
 +
terminates in the left common iliac vein.
 +
 
 +
Glomus Coccygeum. —This so-called gland is situated in front of t
 +
tip of the coccyx. It is about the size of a small pea, and is compos
 +
of a few nodules which are held together and invested by connecti
 +
tissue. It receives the terminal twigs of the median sacral artery,
 +
structure it consists of groups of polyhedral cells united by connecti
 +
tissue, and permeated by blood-capillaries and sympathetic ner\
 +
filaments. It is in some respects similar to the carotid body , whi
 +
is situated behind the common carotid artery of each side close
 +
 
 +
its bifurcation, but differs from it in not containing chromap]
 +
cells.
 +
 
 +
Sacral Glands. —This group comprises a few lymphatic glands whi<
 +
he in front of the sacrum to the inner side of the second and third saci
 +
foramina. They receive their afferent vessels from the various peh
 +
viscera, as well as from the posterior wall of the pelvis; their effere
 +
vessels pass to the middle chain of common iliac glands.
 +
 
 +
Sacral Sympathetic Trunk. —This is situated close to the inner si(
 +
of the anterior sacral foramina. The two trunks, right and left, co
 +
verge as they descend, and in front of the coccyx they are connect*
 +
by a loop which sometimes presents a single ihedian ganglion, called tl
 +
ganglion impar or coccygeal ganglion. The number of ganglia on ea(
 +
trunk is usually four.
 +
 
 +
 
 +
THE ABDOMEN
 +
 
 +
 
 +
947
 +
 
 +
 
 +
b
 +
 
 +
 
 +
 
 +
 
 +
Branches.— (i) Grey rami communicantes, which spring from the  
 
rlia. and pass to the anterior primary divisions of the sacral and  
 
rlia. and pass to the anterior primary divisions of the sacral and  
 
ygeal nerves. These rami are very short. (2) Visceral branches  
 
ygeal nerves. These rami are very short. (2) Visceral branches  

Revision as of 22:52, 29 June 2020

two lacteals, they originate in the fom a loop. The wall of the lacteal vess( formed by a single layer of endothelial pk which are connected by processes with branched cells of the retiform tissue of adenoid tissue. The vessel is ensheathec longitudinal plain muscular fibres der; from the muscularis mucosae, their fi cells being connected with the basen membrane of the villus. The villus is vaded by adenoid tissue—that is to retiform tissue with its meshes filled a amoeboid lymph corpuscles. The branc cells of this retiform tissue are connectec processes, on the one hand, with the er thelial plates which compose the wall of lacteal vessel, and on the other hand ^ the cells of the basement membrane near surface, and these latter in turn send processes between the columnar epith cells of the free surface.

The villi play a most important par absorption, partly through their cop capillary networks, and partly through t lacteals. The lacteals serve specially for absorption of fats, which is probably effected in the following man the columnar epithelial cells at the free surface take up the sapon) and emulsified fats, which they transfer to the amoeboid lymph )


Duodenal Glands


Fig. 500.—Section of the Duodenum, showing Duodenal Glands (highly magnified).




































THE ABDOMEN


867

iscles between them. These corpuscles then carry the fats inwards rough the adenoid tissue into the lacteal vessel.

Duodenal glands (Brunner’s glands) are confined to the duodenum, id are serially continuous with the pyloric glands of the stomach, ley are very numerous in the commencement of the duodenum, iere they form a continuous layer of gland tissue extending as low the entrance of the bile-duct and pancreatic duct. Beyond this ant they gradually diminish in number, and ultimately disappear ar the duodeno-jejunal flexure. They belong to the class of race3 se or acmo-tubular glands,, and they differ from the pyloric glands the stomach in having their tubules more branched and in having


Villus ____


Intestinal Gland


Solitary Nodule Muscularis Mucosas


Submucosa


Circular Muscular Fibres


>ngitudinal Muscular Fibres

Peritoneal Coat __=§§§=


’Mucosa


Fig. 501. —Vertical Transverse Section of the Small Intestine

(highly magnified).


iger ducts. Otherwise the structure of the two kinds of glands is nlar. The duodenal glands lie embedded in the submucous coat, i their long ducts pass through the whole thickness of the mucous d, upon the surface of which they open between the intestinal glands, tte of them, however, open into these glands. The glands can easily displayed by removing the peritoneal and muscular coats of the ^denum and a little of the submucous areolar tissue, when they ^ear as small, round, grey-coloured masses like millet seeds, varying diameter from T V to inch.

the intestinal glands (crypts of Lieberkiihn) are found in large fibers over the whole of the mucous membrane of the small intestine, well as that of the large bowel. They belong to the class of simple



































868


A MANUAL OF ANATOMY


tubular glands, and are to be regarded as small diverticula of tl mucous membrane. Each gland takes the form of a simple tub which is closed and slightly enlarged at its deep extremity, and opei by its other end on the surface between the villi. The glands a] present on the circular folds as well as in the intervening parts. The are placed vertically and close together, and are confined entirely to tf mucous coat, in which they extend from the free surface to the musci laris mucosae. In length they vary from ^ to yTq inch. Each glan is composed of a basement membrane lined with columnar epitheliun and the lumen is of large size.

The solitary nodules are present over the whole extent of the mucoi membrane of the small intestine. They assume the form of small, whit round, or oval nodules, which project by their deep ends into the sul mucous coat, whilst their superficial ends give rise to slight elevatior of the free surface, where they have the openings of the intestin; glands placed around them. They are found upon, as well as betweei the circular folds. In structure each solitary nodule is composed ( adenoid tissue containing large numbers of lymph corpuscles, and pe: meated by capillary networks. Each nodule is surrounded at its dee part by a copious plexus of lymphatic vessels, or by lymphatic sinuse The solitary nodules are simply lymphoid tissue.

The aggregated nodules (Peyer’s patches) are peculiar to the sma intestine, and average about thirty in number in the adult, bein

more numerous in early life. They are situate along the free or anti-mesenteric border of th bowel, which must therefore be opened alon its attached or mesenteric border in order t preserve them. They are largest, best market and most plentiful in the lower half of the ileun In the upper part of the ileum and lower pai of the jejunum they become smaller and mor scarce, and they disappear as a rule above th centre of the jejunum. They vary in lengt from inch to 4 inches, their breadth rangin from J inch to 1 inch. They are for the mos part oblong, their long axis coinciding with tha of the bowel. In the upper part of the ileui and lower part of the jejunum, however, the are somewhat circular. Each aggregated nodul is composed of a group of solitary lymphoi nodules, surrounded by lymphatic plexuses c lymphatic sinuses. The area of each aggregate nodule is slightly elevated, and there are no vil over the lymphoid nodules, whilst the opening of the intestinal glands are arranged in


Fig. 502.—An Aggregated Lymphoid Nodule.


circular manner round each nodule. There are no circular folds ove the aggregated nodules. The aggregated nodules are best marke in young persons. Towards middle life they fade away, and in ol









THE ABDOMEN 869

persons they are usually only distinguishable as discoloured portions of the mucous membrane.

Blood-supply—Arteries.—The duodenum receives its arteries from the superior pancreatico-duodenal of the gastro-duodenal from the hepatic, and the inferior pancreatico-duodenal of the superior mesenteric. The jejunum receives its arteries from the jejunal branches of the superior mesenteric. The ileum receives its arteries from the ileal arteries, and its terminal part in addition receives its arterial supply from the ileal branch of the ileo-colic from the superior mesenteric.

Veins.—The destination of the venous blood of the small intestine is the superior mesenteric vein, and thereafter the portal vein. The veins are provided with valves which are competent in early life, but in the adult they are incompetent, and therefore allow regurgitation of blood to take place towards the small intestine, as happens in cases of portal obstruction.

Lymphatics.—These form a copious plexus of valved vessels, which is situated in the submucous coat. This plexus receives the lymphatics of the mucous membrane and the lacteals of the villi, and it surrounds the deep ends of the solitary nodules. Its efferent vessels pierce the muscular coat, and in doing so they take up the lymph from an intramuscular plexus of lymphatics, which lies between the longitudinal and circular layers. They then leave the bowel at the mesenteric border, where they pass between the two layers of the mesentery, and on their way to the cisterna chyli they traverse the superior mesenteric glands.

Nerves.—These are derived from the superior mesenteric sympathetic plexus, and they form two gangliated plexuses of nonmedullated nerve-fibres. One of these is situated in the muscular coat between the longitudinal and circular layers, and is known as the myenteric plexus (Auerbach’s plexus) (plexus of the muscular coat of the intestine). The other is situated in the submucous coat, and is called the plexus of the submucosa (Meissner’s plexus). The branches of this latter plexus are distributed to the muscularis mucosae and the mucous membrane with its villi.

Characters of Different Parts of the Small Intestine—Duodenum — Peritoneum. —There is no mesentery and only a partial investment of peritoneum. Muscular coat. —This is very thick. Submucous Coat.- —-This contains the tubular portions of the duodenal glands. Mucous Coat .—The characters of this coat are as follows: (1) circular folds, except in the first 1 or 2 inches, (2) villi, (3) intestinal glands, (4) solitary nodules, (5) ducts of the duodenal glands, (6) common orifice of the bile-duct and pancreatic duct, and (7) orifice of the accessory pancreatic duct.

The diameter of the duodenum is from 1^ to 2 inches.

Jejunum — Peritoneum. —There is a mesentery, and the bowel is surrounded by peritoneum except along its mesenteric border. Muscular Coat .—This is comparatively thin. Mucous Coat .—This has the following characters: (1) circular folds, (2) villi in abundance, (3) intestinal glands, (4) solitary nodules, and (5) aggregated lymphoid nodules in its lower half.

The diameter of the jejunum is about i-| inches.

Ileum — Peritoneum. —In this respect the ileum resembles the jejunum.


870


A MANUAL OF ANATOMY


Muscular Coat. —This is very thin. Mucous Coat. —The characters of this co, are as follows: (1) circular folds in upper half, but small and sparse, there beii none in the lower half; (2) villi, but in fewer numbers; (3) intestinal gland (4) solitary nodules; and (5) aggregated lymphoid nodules.

The diameter of the ileum is about 1^ inches.

Development of Small Intestine. —The epithelial lining is at first like th

of the stomach, and the muscular coat develops also in a similar way. Vacuol appear in the epithelium, leading in the duodenum to subdivision of the lume but not in the rest of the gut, where, however, they may produce pouches. Vi appear in the upper part first, about the seventh week, and are found throughoi the gut in the fourth month. They may form by the breaking up of longitudin ridges, or may form separately. Glands develop as simple pits between villi the fourth month, first in the upper gut. They tend to branch later. T, duodenal glands seem to be formed from the simple forms by lateral branchii and growth in length during the fourth month. They are not fully formed ; birth, however.

Large Intestine.—The wall of the large intestine, which is sacculate* is composed of four coats—serous, muscular, submucous, and mucou

The serous coat forms a complete investment to the vermifori appendix, caecum, transverse colon, and pelvic colon. As regarc the ascending colon and descending colon, it is incomplete, being absei behind.

The muscular coat (muscularis externa) is composed of plain muscuk tissue disposed in two layers—external or longitudinal, and internal ( circular.

The longitudinal muscular fibres are for the most part collected ini three flat bands, called taeniae coli, except upon the rectum. In tl intervals between these bands there are some longitudinal fibres, but the are very few and scattered. The taeniae, which are about J inch i breadth, commence upon the caecum at the base of the vermiform a] pendix, and they extend along the several parts of the large intestir as far as the rectum, where they spread out and form a continuot covering, which completely surrounds that part of the bowel. Upc the caecum, ascending colon, descending colon, and iliac colon the teni from their disposition are called anterior, postero-internal, and poster* external. Upon the transverse colon they are so placed as to be calle anterior or omental (greater omentum), postero-inferior or free, an superior or meso-colic (transverse meso-colon). They are shorter tha the bowel to which they are applied, with the result that the tube drawn together or puckered, and thus thrown into sacculi. Thei being three taeniae, there are three rows of sacculi between them, an inasmuch as the taeniae are placed at nearly equal distances from eac other, the sacculi are pretty much of equal dimensions. Between th successive sacculi there are constrictions, usually containing fat. Th sacculi give rise internally to large pouches, and the constrictior between the sacculi produce internally sharp crescentic rugae, whic separate the pouches from each other. When the taeniae are divide*: the sacculi and constrictions entirely disappear, and the large bow* becomes elongated into a smooth cylindrical tube. Along the cours of the taeniae there are a number of small processes of peritoneum cor


THE ABDOMEN


871


ining fat, called appendices epiploicae. They are best marked on the ansverse colon and on the upper part of the pelvic colon, and are least arked, as a rule, on the caecum. Except in the case of the transverse )lon, these are chiefly found along the postero-internal taenia, but in le case of the transverse colon they are principally met with along the Dstero-inferior taenia.

The circular fibres are thin and scattered over the sacculi, but in le constrictions between them they become aggregated. Upon the ctum and anal canal they form a thick layer, which in the latter tuation is known as the sphincter ani internus.

The submucous coat is in all respects similar to that of the small Ltestine.

The mucous coat is pale and greyish in colour, except in the rectum, here it is red. Its epithelium is similar to that of the small intestine.

is destitute of circular folds and villi, and consequently presents a

nooth surface. It contains large numbers of intestinal glands, which iound in mucus-secreting goblet cells. It also contains solitary anphoid nodules, which are especially prevalent in the vermiform ppendix and caecum. The deepest part of the mucous coat is formed y the musculans mucosce ( muscularis interna).

Blood-supply—Arteries.—These are as follows: (1) appendicular, >r the vermiform appendix; (2) anterior and posterior caecal, for the mim; (3) colic of ileo-colic and right colic, for the ascending colon; |.) middle colic, for the transverse colon (all branches of the superior lesenteric); (5) left colic, for the descending colon; and (6) sigmoid rteries, for the iliac colon and pelvic colon (the latter two being branches f the inferior mesenteric).

Veins.—The destination of the venous blood of the vermiform ppendix, caecum, ascending colon, and transverse colon is the superior lesenteric vein, whilst the blood of the descending colon, iliac colon, nd pelvic colon is carried into the inferior mesenteric vein. In both ases the further destination of the blood is the vena portae. As in the mall intestine, the veins have valves which are competent in early life, ut not so in the adult.

The lymphatics will be found described on pp. 799 and 802.

Nerves.—These are derived from the superior mesenteric sympathetic plexus and the inferior mesenteric plexus, which latter is an ffshoot from the aortic plexus. The disposition of the nerves correponds with that in the small intestine.

The large intestine diminishes gradually in size from its commencement to its termination. Its diameter varies in different parts, the xtremes being 2\ inches and 1 inch.

Characters of the Large Intestine — Peritoneal Coat. —This presents at frequent ntervals small projections called appendices epiploicae. Muscular Coat. —The ongitudinal fibres are for the most part arranged in three taeniae. Mucous "oat. —This is destitute of ( a ) circular folds, (b) villi, (c) duodenal glands, and d ) aggregated nodules, but it is provided with (1) intestinal glands, and (2) solitary lodules. Outline of Tube. —The bowel presents three rows of sacculi, except in -he vermiform appendix and rectum.


872


A MANUAL OF ANATOMY


Development. —There is nothing remarkable about the epithelial grow which resembles that of the small gut. The lumen is at first very small and walls thick. The bowel begins to enlarge about the time of its entrance ii the belly, but even then is much smaller than the small intestine. Villi deve' in it during the fourth month, but become smaller and less distinct during succeeding months. Glands form between the villi, but the details of their forr tion are not known with certainty. Villi are found in the vermiform appea in the fourth month, with gland formation.


Structure of the Vermiform Appendix.—The vermiform appenc is entirely covered by peritoneum, which forms a more or less compk


Solitary Nodules


Fig. 503.—Transverse Section of the Vermiform Appendix

(magnified).

meso-appendix or appendicular mesentery. It has a muscular coa composed of an external longitudinal and internal circular layer, both < which completely surround it. The submucous coat contains in gre; abundance solitary nodules of large size, and the mucous coat contaii a few solitary nodules, as well as a few intestinal glands. The base < the appendix is situated at a point on an average rather more tha 1 inch below the ileo-colic valve, according to Treves. The openir by which the appendix communicates with the caecum is occasional guarded by a fold of mucous membrane, which is known as the ileo-coll valve (valve of Gerlach).






THE ABDOMEN


873

The vermiform appendix is usually regarded as the remains of the herbivorous aecum. It is also looked upon as an appendage of the lymphoid system, and as ich it would belong to the class of structures represented by aggregated nodules -namely, lymphoid organs.

Ileo-colic Valve (Valve of Tulpius).—This valve is situated at the oint where the terminal part of the ileum opens into the junction etween the caecum and ascending colon. The orifice, as seen from the iterior of the large intestine, has the form of a slightly oblique cleft bout J inch long, and running in an antero-posterior direction. It is ounded above and below by the two segments which form the valve, nd which project into the large intestine. The upper or ileo-colic egment is prominent, and occupies an almost horizontal plane. The


Dwer or ileo-ccecal segment, longer than the upper, is concave superiorly, nd occupies an oblique plane. The anterior part of the cleft is rounded h, whilst the posterior part tapers to a point. The segments meet in ront of and behind the cleft, and form two prominent folds, which are >rolonged round the wall of the bowel for some distance. These folds re known as the frenula. Each segment is composed of two layers »f mucous membrane, one of which belongs to the ileum, and the other 0 the caecum or colon, as the case may be. These two layers are coninuous with each other at the free margin of the segment, and they ontain between them submucous areolar tissue and circular muscular Tres, both of which are derived partly from the ileum and partly from he large intestine. The longitudinal muscular fibres and the serous or >eritoneal coat take no part in the formation of the segments, being








874


A MANUAL OF ANATOMY


continued uninterruptedly from the ileum to the large intestine. ' mucous membrane which covers the opposed surfaces of the segrm belongs to the ileum, and is therefore provided with villi. The muc membrane of the other surfaces—that is to say, the surfaces which I away from each other (downwards and upwards respectively)—be! to the caecum and colon, and are destitute of villi. The villi thus < appear at the margins of the segments. The valve may be descril as being formed by an inversion of the terminal part of the ileum i the large intestine. That part of the ileum, having passed upwa and to the right with a slight inclination backwards, enters the la intestine. As it does so it leaves behind its serous and longitudi muscular coats, and takes with it its circular muscular, submucc and mucous coats, the corresponding coats of the large intest accompanying it in the inversion. The ileo-colic valve prevents regurgitation of the contents of the caecum into the ileum. It generally believed that the mode of action of the valve is as folio 1 when the caecum becomes distended the frenula of the valve are stretcl and exercise traction upon its segments, which are thereby brou| together. The valve is usually represented in figures as it appears wl the caecum has been inflated and dried. In the fresh condition segments of the valve are thick and tumid, and the appearance is ] unlike that of the pyloric valve as seen from the duodenum or of cervix uteri as seen from the vagina; the frenula, again, are much 1 apparent in such a caecum.

For the structure of the rectum, see p. 960.

Development of Positions of the Stomach and Intestinal Canal.

This subject is dealt with shortly on pp. 61-65 and 79-81. These pa should be studied before reading what follows.

Dorsally, the roof of the mid-gut is at first close to the notochord, but, growth goes on, it comes away from this close relationship, drawing out mesoderm between them as it does so, to form the dorsal mesentery, the man in which this change is effected is not quite clear.

At an early stage, therefore, the alimentary tube in the abdomen can described as being short, median in position, extending from the septum tra versum to the cloaca, and, between these limits, making a short curve, com ventrally, and suspended by a median dorsal mesentery. The vitelline duct attached to it at the lowest part of its curve, and as development proceeds 1 intestinal loop lengthens, so that this lowest part of it passes out of the abdon into the ‘ umbilical sac.’ The elongation of the loop implies a correspond! lengthening of the dorsal mesentery opposite it (see Fig. 44).

Stomach. —This is a dilatation of that part of the tube which is resting the septum transversum. Its attachment here lengthens and thins as the li 1 grows in the septum, and at the same time its dorsal mesentery (meso-gastriu is pouched out to the left, carrying the stomach with it, and turning it so tl its left surface becomes somewhat ventral. The pouch of dorsal meso-gastrii is known as the omental bursa.

Intestinal Canal. —This canal is at first very short and almost straight, aij gs has been stated, it communicates freely with the yolk-sac. At this sh there is no indication of a division into small and large intestine. When wide opening leading to the yolk-sac becomes constricted and converted i: the vitelline duct, the intestinal canal undergoes lengthening, and a conspicu'


THE ABDOMEN


8 75


) is formed, which projects into the cavity of the proximal part of the umbilical i, this cavity being a direct prolongation of the coelom or body-cavity. This ) is spoken of as the U-loop. The convexity of the bend of the loop is directed ! ralwards, and the vitelline duct is connected with the convexity. The loop two limbs, which lie at first parallel to each other. One limb is cephalic, >er, or proximal, and leads from the duodenal loop of the gut; the other limb audal, lower, or distal, and leads to the caudal end of the gut. Upon the al limb a bud makes its appearance. This assumes the form of a blind diverlum, or cul-de-sac, which is the rudiment of the ceecum. The appearance of caecal evagination is the first indication of the division of the intestinal canal > small and large intestine. The primitive small intestine is the part on the



Fig. 5 ° 5 - —The U-Loop, 8 mm., just projecting into the Umbilical Sac. Left and right views. Vitelline duct cut Short.


)ximal side of the rudimentary cascum, and the primitive large intestine is the ft extending from the rudimentary caecum to the caudal end of the gut.

The portion of mesentery which is drawn out as the proper mesentery of the loop contains the superior mesenteric artery between its layers. The artery originally continued on beyond the loop as the vitelline artery, but this soon appears and leaves its trunk as the superior mesenteric.

As the stomach lies in the front wall of the rudimentary lesser sac (bursa lentalis), its pyloric end is directed towards the right, and the very short piece the tube which comes next, the future duodenum, lies rather to the right of the ddle line, and is attached to the median common dorsal mesentery by a thick so-duodenum, which projects on that side of it, just below the opening of the ser sac.







8y6


A MANUAL OF ANATOMY


The intestinal tract is thus seen to consist of intra- and extra-abdorr portions, part of the colon being in the abdomen, and the anterior limb of loop being connected with the duodenum by an intra-abdominal duod umbilical loop of gut.

These different parts of the intestinal tract can be seen in Fig. 505, in w the conditions in a 8 mm. embryo simplified are shown from both sides; the lobe of the liver has been cut away to expose the mesentery and gut, for it cc down at this stage on the left side of the bursa omentalis and mesentery a: as the right lobe on the other side. The neck of the umbilical loop of gut p< out between the two lobes of the liver in a deep notch in the ventral edge oJ


Fig. 506.—Left-sided Views of Umbilical Loop at 9 mm. (Above) and 10 1

(Lower Figure).

organ. An angled bend is seen where the hind-gut is continuous with the hin limb of the loop; this is produced by the attachment here to the gut of a retent band in the mesentery, extending from the peri-aortic region in the neighbourhc of the cceliac artery. The angle must not be mistaken for the left colic flexu with which it has nothing to do; it is gradually effaced as development procee and its ultimate position, if it persisted, would be some little distance to 1 left of the mid-point of the transverse colon.

With the exception of the short length of the duodeno-umbilical piece, wh becomes the first coil of the jejunum, the small intestine is formed in the umbili sac, as are those parts of the large gut which become the ascending and right k of the transverse colon. Formed in this sac, the gut enters the abdomen a




THE ABDOMEN


877


ain stage, and within this cavity is finally disposed in its proper situations.

processes that lead to the ‘ rotation ’ of the intestine can thus be divided

descriptive purposes into three stages—the development outside the belly, entrance into the abdomen and the immediate mechanical results of this nge, and the subsequent assumption of the definitive positions.


Fig. 507.—Two Diagrams to show Earlier Stages of Gut and Mesentery within the Belly and in the Umbilical Sac.


First Stage. —The general disposition in the earlier part of this stage can be a in Fig. 507, A and B. It is marked by the fairly rapid growth in length of anterior or proximal limb of the umbilical loop, forming coils. The ruditttary lesser sac enlarges, passing down on the left side of the median abdominal sentery, between it and the liver. Two or three points in connection with the


1. 508.—Schemes of the Umbilical Loop showing the Sort of Growthchanges THAT OCCUR WITHIN IT (SEE TEXT).

ngating proximal limb must be noted, as they are concerned with the subseent entry and disposal of the gut within the belly cavity: in the first place, ' proximal limb lies, from an early stage on the right side * of the loop, as can


  • The immediate cause of this is not certain. It may be due to the position

the stomach, making the duodenum pass towards the right, or it may be iociated with the development of the vitello-umbilical anastomosis, which 3 in the concavity of this part of the limb of the loop, but any definite state"nt on the subject would be unwarranted.







A MANUAL OF ANATOMY


878

be seen in the figures; secondly, the growth of the proximal limb is associated w marked increase in the depth of the corresponding mesentery of the loop, that the distance between the coils of this limb and the superior mesente artery is much increased; the hinder limb of the loop does not grow like 1 proximal limb, and its distance from the artery remains unchanged, whence comes about that the artery gets relatively nearer and nearer to the hinder lii of the loop. At the back of the loop, where it is passing through the open: in the abdominal wall, the artery is still approximately midway between the t limbs, and it is only distal to this that the unequal growth of the constituent pa of the mesentery of the loop leads to the one-sided position of the vessel.

Fig. 509 illustrates the appearance at the end of the first stage. The cseci is now a large dilatation with a conical extremity, placed on the left side of • mass of coils of small intestine. The mesentery of the small gut is long, and 1 superior mesenteric artery is close to the colon and caecum. The bursa omenh really extends caudally along the whole extent of the left side of the int abdominal colon and meso-colon, separating these from the left lobe of the liv in the figure, however, it is shown as somewhat pushed up, to allow the med: colon and meso-colon to be seen. At the end of this stage, then, the intesti: coils are on the right of the caecum and colon in the umbilical sac, the super mesenteric artery is close to the colon and far from the coils, and the bu omentalis is on the left of a ‘ median abdominal septum ’ made of abdominal coi and meso-colon.

Second Stage. —The recession of the umbilical gut within the belly is brou^ about by a fall in ‘ intra-abdominal tension ' resulting from lessened growth-r of the liver. This organ fills all the available space in the abdomen during 1 second month, growing pari passu with the surrounding parts, but in the ea part of the third month its rate of growth falls behind that of these parts. T does not at first affect the mass in the umbilical sac, and is met by increase in 1 amount of blood in the liver vessels, which are consequently dilated. In 1 tenth week, however, approaching the 40 mm. stage, this dilatation of lr vessels may be considered to have reached its maximum, and any further incre; in the capacity of the abdomen calls for the appearance of some additional si stance to fill the space which otherwise must come into being. The umbili coils are alone able to fulfil this role, and the extra-abdominal or amniotic pressi not being lessened by the fall in the growth-rate of the liver, the contents of 1 umbilical sac are pushed by it into the abdomen to compensate for the inter: fall. It is to be noted now that as the coils enter the abdomen the liver can retr; before them by the discharge of blood from its over-dilated vessels. Thus 1 distension of the liver not only leads to the beginning of the intestinal mo ment, but, by its disappearance and the tendency of the organ to return to undistended condition, leads to the completion of the recession and the provis: of space for the entering coils when and where it is needed, without any pressi on these coils.

The movement having started, all the evidence points to it being rapi( completed. Owing to the size of the caecum, possibly also owing to the gr< size of the dilated venous spaces found round it at this stage, and to the srr size and thick wall of the colon, the ccecum is retained in the sac to the last, a the proximal limb passes first into the abdomen. It does this, not en masse, 1 in continuity, slipping into the belly with its mesentery, the elongation of wh allows it to enter the abdomen, although the superior mesenteric vessels a the colic part of the distal limb are still in the sac. But the proximal limb already been seen to be on the right-hand side of the distal limb, so that it ent the abdomen below the right lobe of the liver, which retreats before it—that the coils of intestine enter the belly on the right-hand side of the median colic ‘ septu (Fig. 509) already mentioned. This ‘ septum ' of abdominal colon and mecolon is thus pushed over to the left by the coils, as seen in Fig. 510, and 1 back against the left dorsal wall of the abdomen, the coils lying on its vent (originally right) surface. Crossing in this way to the left, the coils necessak pass below the colic part of the distal limb of the loop and the mesenteric artery, wb*




THE ABDOMEN


879


509


■The Condition within the Gut enters the Abdomen:


Umbilical Sac shortly before the Left and Right Views.







88 o


A MANUAL OF ANATOMY


is, as already seen, associated with this limb. Moreover, in going to the le and in pushing the median septum to this side, the coils have passed on tl dorsal side of the lower part of the omental bursa, which now hangs down ov them; this is the first form of the greater omentum of the definitive state, althou^ there is as yet no adhesion between the overhanging layers and the colon, ( between it and the dorsal wall.

The ccecum is the last structure to enter the abdomen, and, on entering, it li (Fig. 512) on the mass of coils of small intestine. It forms an angle, howeve with the rest of the colon when it lies in this situation, and as the colon is thic' walled, there is a tendency for the bent piece to straighten itself and come in line with the rest; this, and doubtless also the rapid increase in size of the coils the small gut, which now begins, cause the caecum to assume a right dors


Fig. 510.—Diagram of Section through Root of the Loop, showing ho its Cranial Limb, being below and on the Right of the Other, mu:

PASS BELOW THE CAUDAL LlMB AND THE MAIN VESSELS AND PUSH TP

Intra-abdominal Meso-colon to the Left.

Overhanging omental bursa is represented as rolled up.

position with reference to the mass of coils, on the right side of the neck of tl mass, and thus to come into its proper plane. This is found to occur a few da; after the entrance of the gut into the belly, and with its occurrence the secor stage comes to an end.

Third Stage. —It can be understood from a consideration of the figures that tl caecum and end of the colon, when they move to the right, must pass over ti line of the superior mesenteric artery, for the mesentery of the small intestn is attached along the line of the artery on its lower aspect. Thus the cole will come to lie across the duodenum, and the caecum below and to the rig! of this, and the artery will cross the duodenum lower down. This complet the twist of the mesentery of the loop, which finishes the second stage, ar leaves the peritoneal layers now in a position which can be understood from tl scheme in Fig. 463.



THE ABDOMEN


881


The intestines are now essentially in their proper ‘planes/ and the third t e comprises only the developments and extensions in these positions that l to the conditions found m the adult. The descending meso-colon, laid


. 511.— Scheme to show Result >f Entry of Proximal Limb to rHE Right of Median Septum,

VHICH IT PUSHES TO THE LEFT >lND Dorsally against the Dorsal Wall: Cecum remains n the Sac.


Fig. 512.—Conditions immediately

AFTER THE ENTRANCE IS ACCOMPLISHED.

The caecum and mesenteric vessels lie on the mass of coils, the vessels to the right.


k against the left dorsal wall, as seen in Fig. 463, is, at the beginning of this

  • e, relatively short, so that the left colon only reaches the inner edge of the

it aspect of the left kidney; as growth proceeds, this meso-colon lengthens,


5 r 3 -—Actual Conditions in Embryo just after Cecum has entered the Belly at the End of Second Stage.


1 the colon thus comes to lie farther out, finally reaching its definitive position, 1 the meso-colon becomes adherent to the dorsal wall. This dorsal adhesion presses from within outwards, and when the colon has reached its final posi 56



882


A MANUAL OF ANATOMY


tion, extends to the line of the gut, and thus fixes the bowel in situ. Or right side the colon, about the end of the third month, becomes attached v it crosses the duodenum, and at its caecal end. Between these two fixed the colon and meso-colon are free at first, but attachment of the meson just to the right of the superior mesenteric vessels is soon found. The l between the fixed parts slowly lengthens as the liver gets relatively sm and as it lengthens it becomes curved out with a convexity upwards and t right, ultimately forming in this way the hepatic flexure with the ascei and right portion of the tranvserse colon. The formation of these parts slow process, not really completed at birth. It is accompanied by an extei of the area of meso-colic adhesion, this, however, falling short of the lii advancing colon, so that this is free to lengthen farther. Thus the mesopart of the original loop mesentery becomes attached to the dorsal wall, the


Fig. 514.— Schemes to show Position of Meso-colon and Colon at Var

Stages, indicated by the Measurements.

a, b, left and right mesocolons; t, position at birth.

remaining free as the mesentery of descriptive anatomy; the line of attack of the mesentery is therefore in reality the limit of adhesion of the right meso-cc Between the upper end of the fixed meso-colon on the left and the att ment to the duodenum on the right the free colon and meso-colon are apj to the dorsal aspct of the lower part of the rudimentary lesser sac, invagina this somewhat. The colon stands away from the dorsal wall here, and it is dorsal surface of the meso-colon, the surface continuous with the adhe surfaces of the right and left meso-colons, that is applied (see Fig. 463) to wall of lesser sac. The adhesion of these applied parts to each other, extendir far as the position of the pancreas in the wall of lesser sac, brings into existence transverse meso-colon and the incidental attachment of the greater omentum tc transverse colon', by extension of the adherent area the bursal wall above pancreatic line becomes fixed to the dorsal wall, and constitutes the posU wall of the small sac.

Caecum and Vermiform Appendix. —The caecum appears about the week of embryonic life as a bud in connection with the distal limb of the U








THE ABDOMEN


883


intestine. It assumes the form of a blind diverticulum, which is at first of liform dimensions. It soon, however, becomes conical. The proximal part idergoes enlargement, and represents the permanent caecum. The distal part mains long and narrow, and represents the vermiform appendix, which ultimately jcomes connected with the left and posterior part of the caecum. The various )sitions occupied by the caecum and its migration to the right iliac fossa have st been referred to. Suffice it to say that it lies at first on the left side of the edian line, then it crosses to the right side, being at this stage below the liver, id finally is left in position as the liver retracts.


Peritoneal Structures.

1. Meso-gastrium. —It has been pointed out that the part of the dorsal minion mesentery which carries the stomach becomes pouched out to the left ; ie resulting sac is frequently termed the meso-gastrium, but more appropriately le rudimentary lesser sac (bursa omentalis). Its opening, to the right, is just x>ve the thick part of the mesentery known as the meso-duodenum, and is datively small. The sac is the result of rapid increase of a right-sided depression

the mesentery, the pneumato-enteric recess ; a left-sided recess shows itself

sry early, but disappears almost at once. The opening corresponds in the iult with the line of the pancreatico-gastric folds. The portion of the lesser sac etween these and the opening into lesser sac is added later as an additional

cess to the right of the mesenteric line, associated with the growth of the

iferior vena cava.

The rudimentary lesser sac is at first ‘ free ’ towards the left. After the return E the bowel, which (see Fig. 511) has caused the colon to invaginate its lower rail, the dorsal wall of the sac becomes attached to the abdominal wall, while the olon becomes fixed to its lower aspect. Thus the left half of the transverse leso-colon comes into existence, attached dorsally, while the pancreas, which ad extended in the back layers of the sac, now becomes fixed dorsally, the tyers behind it disappearing. The spleen forms in the outer part of the sac all, which, as the result of the fixation just described, has now a dorsal attachlent towards the left.

The outer part of the sac wall, thus left still ' free,’ is therefore the structure

rmed the ‘ meso-gastrium’ in the adult; the spleen, placed in this, is held by

to the dorsal wall on the one hand (lieno-renal fold) and, on the other, to the

omach (gastro-splenic ligament).

The greater omentum is evidently made by the bulging of the front and lower art of the rudimentary sac over the colon, to which it acquires a secondary ttachment. The lesser omentum (ventral mesentery) is drawn out from the upturn transversum.

2. The meso-duodenum is a thickening of the median mesentery just below the pening into the lesser sac. The duodenum is attached on its right front, and 1 at first a very short segment of the tube. The two pancreatic outgrowths ccur into the meso-duodenum, the upper one being immediately below the pening into lesser sac and opposite the attachment of its lower and back wall, ito which it extends. The lower growth, forming the head of the gland, enlarges 1 the meso-duodenum, with corresponding lengthening of the duodenum, which Iso begins to assume a curved form round the growing head. The whole curve f the duodenum is ultimately formed in this way as a result of the growth of the ead of the pancreas. It is clear, then, that this curve has nothing to do with tie rotation of the gut returning to the abdomen, but it is possible that the xtreme end of the duodenum may belong to the commencement of the proximal nib of the loop, secondarily fixed in position.

3 - Caecum. —The caecum, being originally a bud or outgrowth of the gut, has o mesentery, and is originally entirely surrounded by peritoneum.

4 - Vermiform Appendix. —The vermiform appendix, being originally the find narrowed end of the caecum, or, in other words, a diverticulum of the ‘Scum, is also destitute of a mesentery, properly so called, and is invested by


884


A MANUAL OF ANATOMY


an extension of the peritoneal envelope of the caecum. There is, however, most cases a fold of peritoneum pertaining to the vermiform appendix, whi extends along it for about one-half or two-thirds of its length. This fold called the meso-appendix or appendicular mesentery, and it is derived from t left or inferior layer of the mesentery proper, close to the ileo-colic junctic Its presence is due to the drawing out of vessels as the appendix is formed.


Structure of the Liver.


The liver has two coats, external and internal. The external serous coat is formed by the peritoneum, and is incomplete (see p. 77* Within the serous coat is the fibrous or areolar coat, which is kno\ as the fibrous capsule of the organ. It is for the most part thin, exce where the peritoneal coat is deficient. It is continuous all over t surface with the scanty amount of areolar tissue which pervades t interior of the organ and connects the hepatic lobules. At the por hepatis it surrounds the common hepatic duct, hepatic artery, ai vena portae, under the name of the capsule ofiGlisson. The subdivisio of this capsule accompany the various branches of the duct, arter and vein as these ramify throughout the liver in the portal cana'

The liver substance is composed of a gre number of small polyhedral masses, call hepatic lobules, which are closely pack< together, and at the centre of each of whi< is an intralobular or central vein. In m< there is very little areolar tissue between t] lobules, which are therefore for the most pa confluent. In some animals, however, notab the pig and camel, there is a very distin amount of areolar tissue between the lobule which therefore stand clearly apart from ea( other.

The average diameter of a hepatic lobule aV inch. One of its surfaces is called the has It is by this surface that the lobule is set upc the wall of a sublobular vein, and the intr lobular or central vein, having emerged fro: the lobule through the centre of its bas


Fig. 515.—Section of the Liver, showing a Large Hepatic Vein and its Tributaries (after Kiernan).


opens at once into the sublobular vein. The lobules, therefore, rel tively to the sublobular veins, on which they are ranged, are sessil When a sublobular vein is opened and viewed from within, an appearara something like mosaic work presents itself, the closely-set bases of tt lobules being visible through the thin wall of the vein, and the minut opening of the intralobular or central veins appearing in the centre ( each base. Each lobule is composed of hepatic cells, permeated b capillary networks of bloodvessels and bile-capillaries.

Bloodvessels. —The liver derives its blood from two sources—namely the portal vein and the hepatic artery. These two vessels, togethe with the hepatic duct, are invested by the capsule of Glisson at th























THE ABDOMEN


885

>rtal iissure. Iheir several branches, ensheathed by prolongations of lisson's capsule, ramify from this point throughout the liver, being intained in the system of canals known as portal canals. Each of these nals contains (1) a branch of the portal vein, (2) a branch of the jpatic artery accompanied by a plexus of nerves, (3) lymphatic vessels, id (4) a minute duct, all these being loosely surrounded by a prolonuaDn of Glisson’s capsule.

The portal vein ramifies within the liver like an artery. In the irtal canals its branches receive as tributaries small capsular and ginal veins , and they go on ramifying until they arrive at the interbular areas. Here they anastomose freely with one another around e lobules, and so form the interlobular plexuses . The branches which ise from these plexuses enter the lobules on all sides except their tses, and form in the interior of each lobule an intralobular plexus. -om this plexus a few radicles converge towards the centre of the bule, where they form by their lion the intralobular or central vein. le portal blood, though dark in lour, is very rich, being derived Dm, amongst other sources, the Dmach and small intestine.

The hepatic artery is a branch of n e coeliac artery. As its branches iverse the portal canals they give f capsular branches to the fibrous psule of the liver, and vaginal inches, which supply the walls of e vessels in the portal canals, as ill as their Glissonian sheaths. The anches of the artery finally end minute interlobular arteries , which pply the walls of the interlobular

ins and bile-ducts. According to Fig. 516.—Two Hepatic Lobules me authorities they send minute (highly magnified).

pillary branches into the interior lobule showing the intralobular each lobule to join the mtra- plexus; B, lobule showing the

Dular plexus of the portal vein, but hepatic cells,

is view is not held by others.

The function of the hepatic artery and its branches is to nourish e tissues of the liver, whilst the portal blood supplies the materials fich are elaborated by the hepatic cells.

( The hepatic veins commence in the centre of each lobule as an ralobular or central vein. The intralobular veins open into the blobular veins, which are closely adherent to the bases of the lobules.

sublobular veins join to form larger sublobular veins, and these turn terminate in the hepatic veins, which are not in direct contact th the lobules. The hepatic veins pass to the fossa for vena cava on 2 posterior surface of the liver, towards which they converge, taking









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A MANUAL OF ANATOMY


up sublobular veins in their course. The passages which contain t veins are known as the hepatic canals. On arriving at the upper p; of the fossa for vena cava they are reduced to two or three in numb which pour their contents directly into the inferior vena cava. It is be noted that the hepatic veins converge to the fossa on the poster surface, whilst the branches of the portal vein radiate in all directic from the portal fissure. The hepatic veins are accompanied only lymphatic vessels, and are surrounded by a very scanty amount areolar tissue, which explains why they present open mouths when c across.

Distinguishing Characters of the Hepatic and Portal Veins—Hepatic Veins

(i) These present open mouths when cut across. (2) They are accompan only by lymphatic vessels. (3) Their walls are very thin, and are practica in direct contact with the substance of the liver. (4) They converge towa: the caval fossa on the posterior surface.

Portal Veins. —(1) The mouths of these veins are practically closed or c lapsed when cut across. (2) The veins are accompanied by branches of hepatic artery, and by ducts. (3) Their walls are fairly thick, and are separa from the substance of the liver by the sheaths derived from Glisson’s capsi (4) They radiate in all directions from the porta hepatis in portal canals.

Hepatic Cells.— These are situated within the lobules. 1 hey c polyhedral, granular cells, having a diameter of T 7 T u_ inch, and ea contains a round nucleus. They have no cell-wall, properly so call* and they are connected by a delicate supporting tissue. Ihe ce. which are capable of amoeboid movement, lie between and around t capillary vessels, where they are arranged in radiating rows convergi towards the centre of the lobule.

Bile-ducts. —These commence within the lobules as bile-capillar or bile-canaliculi , which are in reality intercellular passages. Th have a very delicate wall, and are bounded on all sides by the hepa cells—hence the name intercellular passages. According to Pflih and Kupffer, the cells contain vacuoles, which communicate by int: cellular passages with the bile-capillaries. The hepatic cells intern between the bile-capillaries and the capillary bloodvessels. At t circumference of the lobule the bile-capillaries pass into the sm interlobular bile-ducts. These join to form larger ducts, and these turn go on joining until, on arriving at the porta hepatis, only t ducts result, which emerge one from each lobe. These now join to fo: the common hepatic duct, and this joins the cystic duct to form the bi duct. The walls of the interlobular ducts are very thin, being co posed of a basement membrane lined with polygonal epithelium. Tlarger ducts in the portal canals have thicker walls, which, from withe inwards, are composed of a fibro-elastic coat, containing plain muscu tissue, arranged longitudinally and circularly, and a mucous coat lir with columnar epithelium. The mucous membrane of the larger du< presents numerous openings, which lead into blind mucus-secreti recesses. The structure of the hepatic and bile-ducts is similar to t preceding, though on an increased scale.


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887

Lymphatics.—The lymphatic vessels of the liver are arranged in 0 groups—superficial and deep.

Superficial Lymphatics.—These form plexuses beneath the perileal coat, and have different destinations.

Supero-anterior Surface. —(1) The lymphatics from the vicinity of 3 falciform ligament enter that ligament, and, passing through the iphragm into the thorax, they terminate in the anterior group of the pradiaphragmatic glands. (2) The lymphatics from the right part the superior surface and those from the right lateral surface enter 3 right triangular ligament, and, ssing through the diaphragm, they -minate in the middle group of the perior diaphragmatic glands of the r ht side. (3) The lymphatics from 3 left part of the superior surface d those from the left extremity ter the left triangular ligament, and ss to the peri-cesophageal glands in ation to the lower end of the >ophagus, the efferent vessels of lich terminate in the cceliac glands.

1 The lymphatics from the anterior rt of the supero-anterior surface, cept those from the vicinity of the ciform ligament, turn round the terior border of the liver, and end the hepatic glands within the lesser lentum. (5) The lymphatics from ^ 517 ' Lymph Glands in the

e posterior surface of the right lobe Rouviere). ss between the two layers of the HEP, hepatic group,round the artery ronary ligament, and, having pierced and concerned with deep hepatic e diaphragm, they terminate in the na caval group of diaphragmatic mds within the thorax.

Inferior Surface. — (1) The lymtatics from the greater part of the ferior surface of the right lobe, intding those of the quadrate lobe, ss to the hepatic glands. (2) The lymphatics from the posterior ad of the inferior surface of the right lobe pierce the diaphragm, td end in the caval glands. (3) The lymphatics from the greater ad of the caudate lobe pierce the diaphragm, and end in the caval mds ; whilst those from the lower part of this lobe pass to the hepatic mds. (4) The lymphatics from the inferior surface of the left lobe ss to the hepatic glands.

Deep Lymphatics.—These vessels form two distinct sets. Some them accompany the branches of the portal vein, and having emerged rough the porta hepatis, they terminate in the hepatic glands. Others


drainage; B, a cystic gland above, and (below) a gland connected with this and with the retroduodenal gland ; D, above the head of pancreas. These glands are njore particularly concerned with the drainage of the system of biliary ducts.







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A MANUAL OF ANATOMY


pass with the hepatic veins to the caval fossa of the liver, and thereal they enter the thorax along with the inferior vena cava, their destinat being the caval glands.

Nerves.—The nerves of the liver are derived from the hepatic plex which is an offshoot of the coeliac plexus. The coeliac plexus, thoi principally composed of sympathetic fibres, is reinforced by a 1 twigs from the right vagus nerve. The hepatic plexus accompanies hepatic artery to the porta hepatis, where it receives branches from left vagus nerve, which have ascended from the antero-superior surf of the stomach between the two layers of the lesser omentum. In liver the nerves, which are chiefly non-medullated, are distributed the walls of the bloodvessels and ducts, penetrating as far as the inf spaces between the hepatic cells.

Development of the Liver.

Liver. —The hepatic cells and the epithelium of the bile-ducts are of er dermic origin, whilst the connective tissue of the gland and its vascular c stituents are developed from the mesoderm.

The rudiment of the liver appears as a longitudinal groove on the inner asp of the ventral wall of the duodenal portion of the primitive gut. This gro<


Fig. 518.— Sagittal Section through Septum Transversum and Caud End of Fore-gut in an Embryo of 4-5 Mm., to show Hepatic Divi

TICULUM AND GROWTH OF HEPATIC CYLINDERS AND GALL-BLADDER.

The cylinders have broken up the vitelline veins, represented here by the por vein, into sinusoids. The entoderm is shown by solid black.

gives origin to a diverticulum or evagination of the entoderm of the vent duodenal wall, called the hepatic diverticulum or liver-bud, which has at firsi wide communication with the gut. At a later period this communication becon constricted, and forms a pedicle, which, after undergoing elongation, gives r to the bile-duct. From this pedicle, close to the duodenal wall, the venti diverticulum of the pancreas arises.





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889


The hepatic diverticulum