McMurrich1914 Chapter 17: Difference between revisions
mNo edit summary |
mNo edit summary |
||
| Line 865: | Line 865: | ||
4th month. | 4th month. | ||
Crest 1 Sth year. | Crest 1 Sth year. | ||
Patella | Patella | ||
| Line 884: | Line 878: | ||
20 th year. | 20 th year. | ||
Femur | Femur | ||
Revision as of 02:33, 17 June 2016
Embryology - 19 Apr 2024    Expand to Translate
|
|---|
| Google Translate - select your language from the list shown below (this will open a new external page) |
|
العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt These external translations are automated and may not be accurate. (More? About Translations) |
McMurrich JP. The Development Of The Human Body. (1914) P. Blakiston's Son & Co., Philadelphia, Pennsylvania.
| Historic Disclaimer - information about historic embryology pages |
|---|
 |
Chapter XVII. Post-Natal Development
In the preceding pages attention has been directed principally to the changes which take place in the various organs during the period before birth, for, with a few exceptions, notably that of the liver, the general form and histological peculiarities of the various organs are acquired before that epoch. Development does not, however, cease with birth, and a few statements regarding the changes which take place in the interval between birth and maturity will not be out of place in a work of this kind.
The conditions which obtain during embryonic life are so different from those to which the body must later adapt itself, that arrangements, such as those connected with the placental circulation, which are of fundamental importance during the life in utero, become of little or no use, while the relative importance of others is greatly diminished, and these changes react more or less profoundly on all parts of the body. Hence, although the post-natal development consists chiefly in the growth of the structures formed during earlier stages, yet the growth is not equally rapid in all parts, and indeed in some organs there may even be a relative decrease in size. That this is true can be seen from the annexed figure (Fig. 281), which represents the body of a child and that of an adult man drawn as of the same height. The greater relative size of the head and upper part of the body in the child is very marked, and the central point of the height of the child is situated at about the level of the umbilicus, while in the man it is at the symphysis pubis.
That there is a distinct change in the geometric form of the body during growth is also well shown by the following consideration. (Thoma). Taking the average height of a new-born male as 500 mm., and that of a man of thirty years of age as 1686 mm., the height of the body will have increased from birth to adolescence
- v _â–
= 3.37 times. The child will weigh 3.1 kilos and the man
5::
66.1 kilos, and if the specific gravity of the body with the included gases be taken in the one case as 0.90 and in the other as 0.93, then the volume of the child's body will be 3.44 liters and that of the man's 71.08 liters, and the increase in volume will be - - =20.66.
Fig. 281. - Child ast> }vL\x Drawn as of th* " Growth of the Brain, " Contemporary Science Series Sons.)
If the increase in volume had taken place without any alteration in the geometric form of the body, it should be equal to the cube of the increase in height; this, however, is 3-37 s =38.27, a number wellnigh twice as large as the actual increase.
But in addition to these changes, which are largely dependent upon differences in the supply of nutrition, there are others associated with alterations in the general metabolism of the body. Up to adult life the constructive metabolism or anabolism is in excess of the destructive metabolism or katabolism, but the amount of the excess is much greater during the earlier periods of development and gradually diminishes as the adult condition is approached. That this is true during intrauterine life is shown by the following figures, compiled by Donaldson:
Age in Weeks
Weight in Grams
Age in Weeks
Weight in Grams
o (ovum)
o . 0006
24
635
4
-
28
1,220
8
4
32
1,700
12
20
36
2,240
16
120
40 (birth)
3,250
20
28 5
From this table it may be seen that the embryo of eight weeks is six thousand six hundred and sixty-seven times as heavy as the ovum from which it started, and if the increase of growth for each of the succeeding periods of four weeks be represented as percentages, it will be seen that the rate of increase undergoes a rapid diminution after the sixteenth week, and from that on diminishes gradually but less rapidly, the figures being as follows :
Periods of Weeks
Percentage Increase
Periods of Weeks
Percentage Increase
8-12 12-16 16-20 20-24
400 500 137 123
24-28 28-32 32-36 36-40
92 39 32 45
That the same is true in a general way of the growth after birth may be seen from the following table, representing the average weight of the body in English males at different years from birth up to twenty-three (Roberts), and also the percentage rate of increase.
Year
Number of Cases
Weight in Kilograms
Percentage Increase
o
45i
3-2
(10.8)
(238)
2
2
14.7*
(36)*
3
41
15-4
4.8*
4
102
16.9
9-7
5
- 93
18. 1
7-i
6
224
20.1
11
7
246
22 .6
12.4
8
820
24.9
10.2
9
1,425
27.4
10
IO
1,464
30.6
"•5
ii
i,599
32.6
6-5
12
1,786
34-9
7
x 3
2,443
37-6
7-7
14
2,952
41.7
10.9
15
3,"8
46.6
11. 7
16
2,235
53-9
15-7
17
2,496
59-3
10
18
2,15°
62 .2
4.9
19
i,438
63-4
1.9
20
851
64.9
2-5
21
738
65-7
1 .2
22
542
67 .0
1.9
23
55i
67 .0
Certain interesting peculiarities in post-natal growth become apparent from an examination of this table. For while there is a general diminution in the rate of growth, yet there are marked irregularities, the most noticeable being (i) a rather marked diminution during the eleventh and twelfth years, followed by (2) a rapid
- From a comparison with other similar tables there is little doubt but that the weight given above for the second year is too high to be accepted as a good average
Age
LbsM
14
1 Z 3 * 5 6 f a 9 ID ft 12 13 14 1$ 16 17 19
II
i
2 3 4-5 6 7 8 9 10 11 12 13 J& I
5 /
5 17 18
Age Lbs/4 " 12 " 10 •■8 " 6 " * ' Z
Fig. 282. - Curves Showing the Annual Increase in Weight in (I) Boys and (II) Girls.
The faint line represents the curve from British statistics, the dotted line that from American (Bowditch), and the heavy line the average of the two. Before the sixth year the data are unreliable. - (Stephenson.)
acceleration which reaches its maximum at about the sixteenth year and then very rapidly diminishes. These irregularities may be more
Consequently the percentage increase for the second year is too high and that for the third year too low.
It may be mentioned that the weights in the original table are expressed in pounds avoirdupois and have been here converted into kilograms, and further the figures representing the percentage increase have been added.
clearly seen from the charts on page 474, which represent the curves obtained by plotting the annual increase of weight in boys (Chart I) and girls (Chart II). The diminution and acceleration of growth referred to above are clearly observable and it is interesting to note that they occur at earlier periods in girls than in boys, the diminution occurring in girls at the eighth and ninth years and the acceleration reaching its maximum at the thirteenth year.
Considering, now, merely the general diminution in the rate of growth which occurs from birth to adult life, it becomes interesting to note to what extent the organs which are more immediately associated with the metabolic activities of the body undergo a relative reduction in weight. The most important of these organs is undoubtedly the liver, but with it there must also be considered the thyreoid and thymus glands, and probably the suprarenal bodies. In all these organs there is a marked diminution in size as compared with the weight of the body, as will be seen from the following table (H. Vierordt), which also includes data regarding other organs in which a marked relative diminution, not in all cases readily explainable, occurs.
ABSOLUTE WEIGHT IN GRAMS.
New-born and Adult.
Liver
Thyreoid
Thymus
Suprarenal Bodies
Spleen
Heart
Kidney
„ . Spmal Brain _; . Cord
I4I-7 1,819.0
4-85 33-8
8.15 26.9
7-05 7-4
10.6 163.0
23.6 300.6
23-3 3°5-9
381.0 1,430.9
5-5 39-iS
PERCENTAGE WEIGHT OF ENTIRE BODY New-born and Adult.
Liver
Thyreoid
Thymus
Suprarenal Bodies
Spleen
Heart
Kidney
Brain
Spinal Cord
4-57 2 -57
0.16 0.05
0.26 0.04
0.23 O.OI
o-34 0.25
0.76 0.46
0-7S 0.46
12 .29 2 .16
0.18 0.06
476
Recent observations by Hammar render necessary some modification of the figures given for the thymus in the above table. He finds the average weight of the gland at birth to be 13.26 grms., and that the weight increases up to puberty, averaging 37.52 grms. between the ages of 11 and 15. After that period it gradually diminishes, falling to 16.27 g rm sbetween 36 and 45, and to 6.0 grms. between 66 and 75. Expressed in percentage of the body weight this gives a value in the new-born of 0.42 and in an individual of 50 years of 0.02, a difference much more striking than that shown in Vierordt's table.
It must be mentioned, however, that the gland is subject to much individual variation, being largely influenced by nutritive conditions.
The remaining organs, not included in the tables given above, when compared with the weight of the body, either show an increase or remain practically the same.
ABSOLUTE WEIGHT IN GRAMS. New-born and Adult.
Skin and Subcutaneous Tissues
Skeleton
Stomach and Musculature , T Intestines
Pancreas
Lungs
611.75 11,765.0
425-5 ii,575-°
776.5 65 28,732.0 1,364
3-5 97.6
54-i 994-9
PERCENTAGE OF BODY-WEIGHT. New-born and Adult.
Skin and Subcutaneous Tissues
Skeleton
Musculature
Stomach and Intestines
Pancreas Lungs
19-73 17.77
13-7 17.48
2 5-05 43-40
2 . 1 2 .06
0. 11 015
i-75 i-5o
From this table it will be seen that the greatest increment of weight is that furnished by the muscles, the percentage weight of which is one and three-fourths times as great in the adult as in the child. The difference does not, however, depend upon the differentiation of additional muscles; there are just as many muscles in the new-born child as in the adult, and the increase is due merely to an enlargement of organs already present. The percentage weight of the digestive tract, pancreas, and lungs remains practically the same, while in the case of the skeleton there is an appreciable increase, and in that of the skin and subcutaneous tissue a slight
Fig. 283. - Longitudinal Section through the Sacrum of a New-born Female Child. - (Fehling.)
diminution. The latter is readily understood when it is remembered that the area of the skin, granting that the geometric form of the body remains the same, would increase as the square of the length, while the mass of the body would increase as the cube, and hence in comparing weights the skin might be expected to show a diminution even greater than that shown in the table.
The increase in the weight of the skeleton is due to a certain extent to growth, but chiefly to a completion of the ossification of the cartilage largely present at birth. A comparison of the weights of this system of organs does not, therefore, give evidence of the many changes of form which may be perceived in it during the period under consideration, and attention may be drawn to some of the more important of these changes.
In the spinal column one of the most noticeable peculiarities observable in the new-born child is the absence of the curves so characteristic of the adult. These curves are due partly to the weight of the body, transmitted through the spinal column to the hipjoint in the erect position, and partly to the action of the muscles, and it is not until the erect position is habitually assumed and the musculature gains in development that the curvatures become pronounced. Even the curve of the sacrum, so marked in the adult, is but slight in the new-born child, as may be seen from Fig. 283, in which the ventral surfaces of the first and second sacral vertebrae look more ventrally than posteriorly, so that there is no distinct promontory.
But, in addition to the appearance of the curvatures, other changes also occur after birth, the entire column becoming much more slender and the proportions of the lumbar and sacral vertebrae becoming quite different, as may be seen from the following table (Aeby) :
Lengths Of The Vertebral Regions Expressed As Percentages Of The Entire Column
Age
Cervical
Thoracic
Lumbar
New-born child
25.6 23-3 20.3 19.7 22 .1
47-5 46.7 45-6 47.2 46.6
26.8
Male 2 years
30.0
Male 5 years
34.2
Male 1 1 years Male adult
33-i 31.6
The cervical region diminishes in length, while the lumbar gains, the thoracic remaining approximately the same. It may be noticed, furthermore, that the difference between the two variable regions is greater during youth than in the adult, a condition possibly associated with the general more rapid development of the lower portion of the body made necessary by its imperfect development during fetal life. The difference is due to changes in the vertebrae, the intervertebral disks retaining approximately the same relative thickness throughout the period under consideration.
The form of the thorax also alters, for whereas in the adult it is barrel-shaped, narrower at both top and bottom than in the middle, in the new-born child it is rather conical, the base of the cone being below. The difference depends upon slight differences in the form and articulations of the ribs, these being more horizontal in the child and the opening of the thorax directed more directly upward than in the adult.
As regards the skull, the processes of growth are very complicated. Cranium and brain react on one another, and hence, in harmony with the relatively enormous size of the brain at birth, the cranial cavity has a relatively greater volume in the child than in the adult. The fact that the entire roof and a considerable part of the sides of the skull are formed of membrane bones which, at birth, are not in sutural contact with one another throughout, gives opportunity for considerable modifications, and, furthermore, the base of the skull at the early stage still contains a considerable amount of unossified cartilage. Without entering into minute details, it may be stated that the principal general changes which the skull undergoes in its post-natal development are (i) a relative elongation of its anterior portion and (2) an increase in the relative height of the maxillae.
If a line be drawn between the central points of the occipital condyles, it will divide the base of the skull into two portions, which in the child's skull are equal in length. The portion of the skull in front of a similar line in the adult skull is very much greater than that which lies behind, the proportion between the two parts being 5:3, against 3:3 in the child (Froriep). There has, therefore, been a decidedly more rapid growth of the anterior portion of the skull, a growth which is asssociated with a corresponding increase in the dorso-ventral dimensions of the maxillae. These bones, indeed, play a very important part in determining the proportions of the skull at different periods. They are so intimately associated with the cranial portions of the skull that their increase necessitates a corresponding increase in the anterior part of the cranium, and their increase in this direction stands in relation to the development of the teeth, the eight teeth which are developed in each maxilla (including the premaxilla) in the adult requiring a longer bone than do the five teeth of the primary dentition, these again requiring a greater length when completely developed than they do in their immature condition in the new-born child.
Fig. 284. - Skull of a New-born Child and of an Adult Man, Drawn as of Approximately the Same Size. - (Henke.)
But far more striking than the difference just described is that in the relative height of the cranial and facial regions (Fig. 284). It has been estimated that the volumes of the two portions have a ratio of 8: 1 in the new-born child, 4: 1 at five years of age, and 2:1 in the adult skull (Froriep) , and these differences are due principally to changes in the vertical dimensions of the maxillae. As with the increase in length, the increase now under consideration is, to a certain extent at least, associated with the development of the teeth, hese structures calling into existence the alveolar processes which ,re practically wanting in the child at birth. But a more important actor is the development of the maxillary sinuses, the practically olid bodies of the maxillae becoming transformed into hollow shells, rhese cavities, together with the sinuses of the sphenoid and frontal >ones, which are also post-natal developments, seem to stand in elation to the increase in length of the anterior portion of the skull, erving to diminish the weight of the portion of the skull in front »f the occipital condyles and so relieving the muscles of the neck of a onsiderable strain to which they would otherwise be subjected.
These changes in the proportions of the skull have, of course, nuch to do with the changes in the general proportions of the face. 3ut the changes which take place in the mandible are also imporant in this connection, and are similar to those of the maxillae in leing associated with the development of the teeth. In the new10m child the horizontal ramus is proportionately shorter than in he adult, while the vertical ramus is very short and joins the Lorizontal one at an obtuse angle. The development of the teeth if the primary dentition, and later of the three molars, necessitates ,n elongation of the horizontal ramus equivalent to that occurring n the maxillae, and, at the same time, the separation of the alveolar •orders of the two bones requires an elongation of the vertical ramus f the condyle is to preserve its contact with the mandibular fossa, ,nd this, again, demands a diminution of the angle at which the ami join if the teeth of the two jaws are to be in proper apposition.
In the bones of the appendicular skeleton secondary epiphysial enters play an important part in the ossification, and in few are hese centers developed prior to birth, while the union of the epiphyes to the main portions of the bones takes place only toward maurity. The dates at which the various primary and secondary enters appear, and the time at which they unite, may be seen from he following table:
31
482
POST-NATAL DEVELOPMENT UPPER EXTREMITY.
Bone
Appearance of
Appearance of Secondary
Fusion of
Primary Center
Centers
Centers
Clavicle
6th week.
(At sternal end) 17th year.
20th year.
Scapula.
Body
8th week. <.
2 acromial 15th year.
2 on vertical border 16th year.
> 20th year.
Coracoid ....
1 st year.
15 th year.
Head 1st year.
Great tuberosity 3d year.
> 20th year.
Lesser tuberosity 5th year.
J
Humerus
â– jth week.
Inner condyle 5th year.
1 8th year.
Capitellum 3d year.
1
Trochlea 10th year.
[• 17 th year.
Outer condyle 14th year.
J
Ulna
jth week.
Olecranon 10th year.
16th year.
Distal epiphysis 4th year.
1 8th year.
Radius
jth week.
Proximal epiphysis 5th year.
17 th year.
Distal epiphysis 2d year.
20th year.
Capita turn
1st year.
Hamatum
2d year.
Triquetrum . . .
3d year.
4th year.
Multangulum
5th year.
majus.
Navicular
6th year.
Multangulum
8th year.
minus.
Pisiform
12 th year.
Metacarpals . . .
gth week.
3d year.
20th year.
Phalanges
gth-nth week.
3d~5th years.
17 th-! 8th years.
The dates in italics are before birth.
POST-NATAL DEVELOPMENT LOWER EXTREMITY.
483
Bone.
Appearance
of
Appearance of Secondary Fusion of
Primary Center
Centers
Centers
gth week.
Crest 15th year.
Anterior inferior spine 15 th year.
V
â– 22d year.
Ischium
4th month.
Tuberosity 15th year.
Pubis
4th month.
Crest 1 Sth year.
Patella
Cartilage appears at 4th month, ossification in 3d year.
Head 1st year.
20 th year.
Femur
â– jth week.
J
Great trochanter 4th year. Lesser trochanter 13 th- 14th year. Condyle gth month.
19 th year. 1 Sth year. 2 1 st year.
Tibia
jth week.
1
Head end of gth month. Distal end 2d year.
2ist-2 5thyear. 1 Sth year.
Fibula
Sth week.
Upper epiphysis 5th year. Lower epiphysis 2d year.
21st year. 20th year.
Talus
jth month.
Calcaneus
6th month.
10th year.
1 6 th year.
Cuboid
A few days after birth.
Navicular
4th year.
Cuneiforms.
1 st year.
Metatarsals
gth week.
3d year.
20th year.
Phalanges
gth-i2th week
4th-8th years.
I7th-i8th years.
The dates in italics are before birth.
So far as the actual changes in the form of the appendicular bones are concerned, these are most marked in the case of the lower limb. The ossa innominata alter somewhat in their proportions after birth, a fact which may conveniently be demonstrated by considering the changes which occur in the proportions of the pelvic diameters, although it must be remembered that these diameters are greatly influenced by the development of the sacral curve. Taking the conjugate diameter of the pelvic brim as a unit for comparison, the antero-posterior (dorso-ventral) and transverse diameters of the child and adult have the proportions shown in the table on the opposite page (Fehling).
It will be seen from this that the general form of the pelvis in the new-born child is that of a cone, gradually diminishing in diameter from the brim to the outlet, a condition very different from what obtains in the adult. Furthermore, it is interesting to note
Diameter.
New-born
Adult
New-born
Female.
Female.
Male.
i .00
1 .00
1 .00
1. 19
1 .292
1 .20
0.96
1. 19
0.91
1 .01
1. 151
0.99
0.91
1.05
0.78
0.83
i-i54
0.84
Adult Male.
(Conjugata vera . Transverse
>, f Antero-posterior
rt 1
U y Transverse
-^ ( Antero-posterior
O Transverse
1.294 1. 18 1. 14 1 .07
1 -153
that sexual differences in the form of the pelvis are clearly distinguishable at birth; indeed, according to Fehling's .observations, they become noticeable during the fourth month of intrauterine development.
The upper epiphysis of the femur is entirely unossified at birth and consists of a cartilaginous mass, much broader than the rather slender shaft and possessing a deep notch upon its upper surface (Fig. 285). This notch marks off the great trochanter from the head of the bone, and at this stage of development there is no neck, the head being practically sessile. As development proceeds the inner upper portion of the shaft grows more rapidly than the outer portion, carrying the head away from the great trochanter and forming the neck of the bone. The acetabulum is shallower at birth than in the adult and cannot contain more than half the head of the femur; consequently the articular portion of the head is much less extensive than in the adult.
It is a well-known fact that the new-born child habitually holds the feet with the soles directed toward one another, a position only reached in the adult with some difficulty, and associated with this supination or inversion there is a pronounced extension of the foot (i. e., flexion upon the leg as usually understood; see p. 102), it being difficult to flex the child's foot beyond a line at right angles with the axis of the leg. These conditions are due apparently to the extensor and tibialis muscles being relatively shorter and the opposing muscles relatively longer than in the adult, and with the elongation or shortening, as the case may be, of the muscles on the assumption of the erect position, the bones in the neighborhood of the anklejoint come into new relations to one another, the result being a modification of the form of the articular surfaces, especially of the talus (astragalus). In the child the articular cartilage of the trochlear surface of this bone is continued onward to a considerable extent upon the neck of the bone, which comes into contact with the tibia in the extreme extension possible in the child. In the adult, however, such extreme extension being impossible, the cartilage upon the neck gradually disappears. The supination in the child brings the talus in close contact with the inner surface of the calcaneus and with the sustentaculum tali; with the alteration of position a growth of these portions of the calcaneus occurs, the sustentaculum becoming higher and broader, and so becoming an obstacle in the way of supination in the adult. At the same time a greater extent of the outer surface of the talus comes into contact with the lateral malleolus, with the result that the articular surface is considerably increased on that portion of the bone. Marked changes in the form of the talo-navicular articulation also occur, but their consideration would lead somewhat further than seems desirable.
Fig. 2S5. - Longitudinal Sections of the Head of the Femur of (.4) New-born Child and (B) a Later Stage of Development. ep, Epiphysial center for the head; h, head; /, trochanter. - (Henke.)
Literature
C. Aeby: "Die Altersverschiedenheiten der menschlichen Wirbelsaule." Archiv fur Anal, und Physiol., Anat. Abth., 1879. W. Camerer: " Utersuchungen iiber Massenwachsthum und Langen wachsthum der Kinder," Jahrbuchfiir Kinderheilkunde, xxxvi, 1893.
H. H. Donaldson: "The Growth of the Brain," London, 1895.
H. Fehling: "Die Form des Beckens beim Fotus und Neugeborenen und ihre Beziehe hung zu der beim Erwachsenen," Archiv fur Gynakol., x, 1876.
H. Friedenthal: " Das Wachsthum des Korpergewichtes des Menschen und anderer Saugethiere in verschiedenen Lebensaltern," Zeit. allgem. Physiol., ix, 1909.
J. A. Hammar: "Ueber Gewicht, Involution und Persistenz der Thymus im Post fotalleben des Menschen," Archiv fur Anat. und Phys., Anat. Abth., Supplement, 1906.
W. Henke: " Anatomie des Kindersalters," Handbuch der Kinder krankheiten (Cerhardt) , Tubingen, 1881.
C. Hennig: "Das kindliche Becken," Archiv fur Anat. und Physiol., Anat. Abth.,
1880. C. Huter: "Anatomische Studien an den Extremitatengelenken Neugeborener und Erwachsener," Archiv fur patholog. Anat. und Physiol., xxv,
1862. W. Stephenson: "On the Relation of Weight to Height and the Rate of Growth in Man," TheLancet, 11, 1888.
R. Thoma: " Untersuchungen iiber die Grosse und das Gewicht der anatomischen Bestandtheile des menschlichen Korpers," Leipzig, 1882.
H. Vierordt: "Anatomische, Physiologische und Physikalische Daten und Tabellen," Jena, 1893.
H. Welcker: "Untersuchungen iiber Wachsthum und Bau des menschlichen Schadels," Leipzig, 1862.
| Historic Disclaimer - information about historic embryology pages |
|---|
|
McMurrich JP. The Development Of The Human Body. (1914) P. Blakiston's Son & Co., Philadelphia, Pennsylvania.
Cite this page: Hill, M.A. (2024, April 19) Embryology McMurrich1914 Chapter 17. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/McMurrich1914_Chapter_17
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
