Paper - Studies of the intestine and peritoneum in the human foetus - part 1
|Embryology - 29 Nov 2023 Expand to Translate|
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Reid DG. Studies of the Intestine and Peritoneum in the Human Foetus: Part I. (1911) J Anat Physiol. 45(2): 73-84. PMID 17232876
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Studies of the Intestine and Peritoneum in the Human Foetus. Part I
By Douglas G. Reid, M.B., Ch.B. Edin., B.A. Trin. Coll. Camb.,
Demonstrator of Anatomy in the University of Cambridge.
These studies are based chieﬂy on the examination of the arrangement of the peritoneum in twenty fetuses in the Cambridge Museum (of which nine were female specimens), varying in length from 12 to 20 cms. (vertex-coccygeal measurement).
In this part I shall describe a peritoneal fold present in eleven (six males and ﬁve females) of the twenty foetuses (55 per cent.). Moreover, there is evidence of its having been present at an earlier stage in at least three others. In order to understand the changes accompanying the presence of this fold, it is necessary to refer to the line of the root of the foetal mesentery. Except in the case of the part ﬁxed to the front of the fourth portion (ascending part of the pars inferior) of the duodenum, the root of the mesentery is attached along a line which is still practically transverse. It is implanted upon the whole of the front of the third portion (transverse part of the pars inferior) of the duodenum, and to the right of this upon the peritoneum covering ‘the front of the right kidney. It to be noted that the root is attached to the posterior abdominal wall exactly along the line of the ileo—colic artery which arises from the superior mesenteric at (never below) the place where this artery crosses the third portion of the duodenum, and courses towards the right. At this stage the surfaces of the mesentery may be described as being superior and inferior. Indeed, the mesentery lies often horizontally for some distance from its root, forming a shelf, supported on its inferior surface by the large intra-abdominally placed pelvic colon. One notes here that the retro—colic fossa in the adult is limited medially by a fold, the 1nesenterico—iliac fold of Jonnesco (plica genito-enterica of Treitz). This is described as being merely the insertion of the mesentery in the iliac fossa, where it has a very variable line of insertion, in the female being continuous (always?) with the broad ligament. The special genito-mesenteric fold (see ﬁg. 1) which I now describe passes downwards from the inferior surface of the mesentery in the right half of the abdomen.
There is nothing corresponding to it on the left side. It forms an antero—posterior septum lying in the vertical plane, incompletely subdividing the portion of the abdominal cavity below the root of the mesentery into two compartments. The smaller of these is to its right side, and contains the caecum; the larger is to its left side, and contains the pelvic colon. The fold is, as it were,.propped up on the sides by these portions of the bowel.
FIG. 1. Foetus No. XI.
The fold is triangular in form. It presents right and left surfaces, both of which are generally free. Of its borders, two are attached: one, the posterior, to the posterior abdominal wall along the line of the right spermatic or ovarian vessels; and the other, the superior or mesenteric, to the inferior surface of the mesentery, often to a considerable extent.
The ileac branch of the ileo-colic artery leaves the fold, in which it lies at the root of the mesentery (to be described later), and courses forwards, away from the posterior abdominal wall, in the substance of the mesentery.
FIG. 2. Foetus No. XIV.
The attachment of the genito-mesenteric fold to the mesentery is generally exactly along the line of this artery. The anterior border of the fold is in most cases free. It is usually continuous below with the suspensory ligament of the ovary, and its inferior extremity appears in consequence truncated. This fold is not to be confounded with a mere dihedral angling of the mesentery, in relation to the ileac branch of the ileo-colic artery, although in some instances the ileum may become adherent to its right side. This adhesion may occur close to the ovary, which thus comes (as in one foetus) to be intimately bound to the ileum. The uniting band here is evidently not a pathological adhesion. However, the continuity of the fold with the suspensory ligament of the ovary is not constant; the two folds may be separate, although lying in line one above the other.
In the male foetuses the fold is not usually continued into the suspensory ligament of the testis—although it may reach to this—saVe through the prominence produced by the spermatic vessels descending behind the peritoneum of the posterior abdominal wall.
In the full-time foetus (ﬁg. 3), in which the genito-mesenteric fold is present, the parts have acquired almost the position which they occupy in the adult, the caecum lying in the right iliac fossa, and the hepatic and splenic ﬂexures in their usual adult position. But the whole of the ascending and transverse colon is free of attachment to the posterior abdominal wall, as is the 1nesentery of the ascending colon, jejunum, and ileum. All ca11 be pulled freely forward. In other words, almost the whole of the peritoneum of the intestinal loop is free. The caecuin having completed its descent, the ileo-colic vessels new take a definitely descending course, in the free peritoneum of the loop, towards the ileo-czecal junction. They lie in the obvious folds of peritoneum, along the line of which the root of the mesentery is usually attached. Had the peritoneum of the intestinal loop become soldered down at these folds, the line of the root of the mesentery would have followed exactly the direction usually taken in the adult. It is true that the root of the mesentery passes down upon the fourth portion of the duodenum; but this is the primitive condition, this part of the duodenum belonging to the intestinal, and not to the duodenal loop. The anterior surfaces of the first, second, and third portions of the duodenum are free (5.0. the peritoneum of the intestinal loop and the transverse colon can be pulled forwards off these parts). The first and second parts of the duodenum are also free behind, as is the posterior surface of the meso—duodenum and the head of the pancreas. But although the peritoneum of the intestinal loop, save where it covers the front of the meso—duodenum, is free of adhesion, on lifting the loop forwards the large triangular genito-mesenteric fold is seen passing from the posterior surface of its peritoneum backwards to the posterior abdominal wall.
The whole appearance is one of a remarkable T—shaped mesentery holding down the intestine, and taking the place of the normal root of the mesentery.
The fold extends downwards to the posterior (internal) abdominal ring. The mesenteric border is attached to the duodenum at the angle between the second and third portions——and it is here that the duodenum descends lowest in the abdomen—as well as to the peritoneum of the intestinal loop along a line 3.8 cms. long.
This line lies to the right of the ileo-colic artery above, but lower down it passes directly along the ileac branch of this vessel, as in the other foetuses. The fold, therefore, would have become reduced in size if the intestinal loop and its peritoneum had become soldered down to the normal extent. The part of the fold related to the ileac branch, along which adhesion does not occur, would, however, have remained.
FIG. 3. Drawn with careful measureliients from a full-time fmtus. two-thirds actual size. Viewed from the right side. The artery is -.1 branch of the right gastro-epiploic (not figured).
Its posterior border, from the duodenum downwards to the internal abdominal ring, is 6.4: cms. long. The anterior, or free, border measures 7.5 cms. in length. The mesenteric border lies an average distance of 2 cms. from the ascending colon, and a large number of lacteal glands lie in the mesentery along the ileac artery. The surfaces of the fold are free, and between their endothelial laminae are many lymphatic glands and a network of blood-vessels, visible to the naked eye. The portion of the great omentum to the right of the pylorus (ac. the right process of the great omentum) extends downwards upon the colon as far as the root of the appendicular caecum. A branch of the right gastro—epiploic artery, lying in this, extends upon the colon to the hepatic ﬂexure (see ﬁg. It then leaves the great omentum and passes over the posterior surface of the upper part of the ascending colon and comes to lie in the mesocolon. Leaving this, it crosses the lower part of the second portion of the duodenum, and gets on to the posterior abdominal Wall, to the right side of the fold. After a curved course, it enters the genito-mesenteric fold at its posterior border, and ﬁnally emerging from the fold at its mesenteric border, again enters the mesentery, and ends on the colon near the caecum. The spermatic vessels lie along the parietal attachment of the fold. Although the second portion of the duodenum is free behind, a thin sheet of peritoneum (see ﬁg. 3) passes from its right border to the front of the right kidney. This sheet lies in a vertical and antero-posterior plane, and its right endothelial lamina is continuous with the corresponding lamina of the genito-mesenteric fold. A s As will be seen from the foregoing description of the duodenum, it forms the right boundary of a large retro—duodenal fossa, which opens above at the foramen of Winslow into the general peritoneal cavity. It presents at the level of the junction of the ﬁrst and second portions of the duodenum a superior free horizontal edge stretching from the duodenum to the kidney. The upper part of this sheet, therefore, is simply the duodeno-renal ligament.
The vessels ramifying upon the anterior surface of the second portion of the duodenum are not so distinctly visible as those seen upon the front of the ﬁrst portion. This is due to the presence of a peritoneal veil which passes from the posterior surface of the peritoneum of the intestinal loop over the front of the second part of the duodenum, to be continuous with the peritoneal sheet, which anchors the right border of the duodenum to the kidney. This veil is also continuous below, like the sheet itself, with the right endothelial lamina of the genito-mesenteric fold.
Certain modifications were found in the line of attachment of the mesentery in foetuses in which the genito-mesenteric fold is present, as well as some examples of visceral adhesions to the fold.
Without an actual alteration in the line of the root of the mesentery occurring, a deep fossa is present in one foetus on the upper surface of the F mesentery, the bottom of the fossa corresponding to the line of attachment of the genito-mesenteric fold.
In two foetuses the ileo-colic artery to the right of the duodenum forms the base of a triangle, the apex of which is below, and the sides of which are placed at the root of the mesentery. The genito-mesenteric fold is attached to the mesentery opposite the apex (73.6. opposite the most depressed part of the mesenteric root).
Again, in two others, although the root of the mesentery retains its intimate relation to the ileo-colic artery to the left side of the fold, the ileum, in the last 1'5 cms. and 2 cms. of its course, adheres ﬁrmly, along with the whole of its mesentery, to the peritoneum of the posterior abdominal wall to its right side, and the ileum also adheres to the right surface of the fold itself. In one of these foetuses the mesentery indeed is also tacked down slightly to the abdominal Wall on the left side of the fold. In this foetus the ileac artery is placed in a fold of peritoneum, J quite 3 mms. high, Which is seen projecting from the upper surface of the mesentery. This arterial fold, since it lies over the genito-mesenteric fold, owes its existence to this tacking down of the mesentery on both sides. It forms a veritable septum, subdividing the marked fossa resulting from this depression of both laminae of the mesentery into a right and left part. In these, and in another foetus, the ileum adheres deﬁnitely to the right side of the genito-mesenteric fold, whose connection with the mesentery is still distinctly seen.
- 1 For a good ﬁgure of this see Spalteholz’s Atlas.
"In two other foetuses the genito-mesenteric fold passes from the non-mesenteric border of the terminal portion of the ileum, and has no apparent connection with the mesentery.
But, in the light of all the other instances, there is little doubt that in these cases the ileum had ﬁrst of all adhered by one of its aspects to the right side of the fold. Through great solidity of soldering of the peritoneal surfaces together, this surface of the ileum became again apparently free.
I have seen a comparably great solidity of fusion in the case of the great omentum, which on this account may appear, even before birth, to have partially disappeared. It may be seen also in the case of the appendix.
Thus in one foetus the genito-mesenteric fold passes from the usually free border of the appendix, and does not appear to be continued over the appendix to the mesentery.
The appendix is connected to the mesentery by a sheet of peritoneum (see ﬁg. 4:, A), which at ﬁrst sight appeared to be simply meso-appendix. But the clue to its real nature is found in the fact that, when viewed from the left (see ﬁg. 4), the artery of the appendicular caecum (Which occupies a distinct fold along the free edge of the meso-appendix) seems suddenly to disappear, becoming suddenly obscured by a peritoneal veil. But when viewed from the right the artery is distinctly visible to the usual extent. The front edge of this veil is continued into the free edge of a sheet of peritoneum above the artery, and thereby passes to the inferior surface of the mesentery. These appearances leave no doubt that not only had the serous coat of the appendix adhered to the right side of the genito-mesenteric fold, a condition seen in another foetus, but that one surface of the meso-appendix, from border to border, had also similarly adhered. Here again the appendix, save at its borders, appears free of the fold; and the explanation of this condition appears to be that it results from solidity of soldering.
A similar arrangement in connection with the appendix and meso-appendix was found in an adult male. Here a slight fold passed downwards upon the external iliac vessels from the usually free border of the appendix. The fold, then, which connected the appendix to the mesentery in these cases is the result of the fusion together of two sheets of peritoneum, and represents genito-mesenteric fold on the left and meso—appendix on the right.
FIG. 4. Fcetus No. X.
We have seen that, in association with the genito-mesenteric fold, the ileum and its mesentery may become adherent to the posterior abdominal wall on the right side of the fold. Similarly, the caecum may become adherent to the posterior abdominal wall on this side. Thus, in one foetus the caecum, its appendix, and the meso-appendix, and with it the “blood-less ” fold of Treves, are ﬁrmly soldered down to the abdominal wall on the right side of the genito-mesenteric fold ; and the “ bloodless fold ” was similarly seen directly adherent to the posterior abdominal wall in associa- tion with this fold. It is essentially on the right of the fold, as well as actually to the right surface of the fold itself, that these adhesions occur.
In only three cases is the genito-mesenteric fold associated with a retro-colic fossa. But in most of the foetuses in which it is present the appendix is deﬁnitely retro-colic.
The genito-mesenteric fold appears to be late in making its appearance, if one can. judge from its absence in a 25-mm. foetus (given to me by Mr John Griffith, B.-A., of Christ’s College). a How this fold is produced is not clear. It is possible that sometimes the right extremity of the great omentum (which is late in appearing) may assist in forming it, perhaps extending in some cases off the colon on to the posterior abdominal wall, and fusing, as it does so, with the right surface of the fold. The presence of the branch of the right gastro-epiploic artery in the fold—and indeed projecting, rather from’ its right surface, as if it had been added on—-and behind the peritoneum of the posterior abdominal wall might thus be explained. It is difficult to see why its mesenteric border should be related to the ileac branch of the ileo-colic artery?
The fold may exercise considerable inﬂuence on parts about it. It is signiﬁcant that the lowest point of the duodenum is at the place of attachment of this fold. This suggests that it exerts a traction upon the duodenum at this part. If this traction be excessive, it may be a cause of downward displacement of the duodenum.
The second part of the duodenum may also adhere to the left side of the fold.
The duodeno-renal sheet and veil of peritoneum already described were formed by the upper part of the genito-mesenteric fold. We may also infer from this foetus that the duodeno-renal ligament of Huschke is practically the upper part of the fold.
In the light of these specimens, and associated with the elongation of the ascending colon and the descent of the genital gland, this fold is evidently a cause of depression and actual tacking down of the mesentery, with a consequent lowering of the mesenteric root, with which the ileo-colic artery may retain or lose, to a greater.or less degree, its close relation.
The fold may also assist in producing adhesion of the duodenum, caecum, and ileum to the posterior abdominal Wall. Adhesion in the adult binding down the terminal part of the ileum, the caecum, the appendix, the mesentery, the meso—appendix, and even the “bloodless” fold of Treves, need not be the result of pathological changes, unless the natural cause We have indicated for the adhesion can be excluded, although a genito-mesenteric fold may not always be seen even in the foetus.
The ovary may be bound, sometimes very intimately, to the ileum or appendix, through the adhesion of these parts of the bowel to the right surface of the fold.
FIG. 5. Foetus No. XVIII. Part of the side wall of the abdomen has been removed.
There is no general shifting of the endothelial layers in such a manner that What was once free peritoneal surface remains free, apparently produced by the genito-mesenteric fold in determining these adhesions.
Its action upon the mesentery is to render a part of it. more immobile ; and through it, apparently, a traction is exerted upon the mesentery.
The genito-mesenteric fold must be of considerable interest from a surgical and gynaecological point of view. Its adhesion may restrict the spread of inﬂammatory exudations. It is the commonest cause of a retro- colic position of the appendix. Its presence, or the adhesions which it produces to the left of the caecum, may arrest the completion of caecal torsion (see ﬁgs. 2, 5,and 6).
- 1 “Morphology of the Digestive Tract,” by Byron Robinson, M.D., Joum. 0] Anat. and Phys., xxxiii. ‘
FIG. 6. Foetus No. XIII.
It may occasionally form the medial boundary of the retro-colic fossa. When the last part of the ileum and the corresponding part of the mesentery adhere to the posterior abdominal wall, the adhesion forms the left boundary of the retro—colic fossa, and the genito-mesenteric fold may liequite to the left of the fossa. It is possible that an inguinal hernia of the caecum and lower part of the ileum may in some cases be produced by the traction of the fold if it has been connected with the suspensory ligament of the testis during the passage of this organ to the scrotum. A further inquiry Will have to be made into its relations to the lymphatic vessels.
We have already noted the presence in the fold of a large number of lymphatic glands; and the possibility that through it the lymphatic vessels of the genital gland in each sex, appendicular caecum, ileum, duodenum, and stomach, may be thrown into communication with one another has to be kept in mind. As I shall describe later, the fold may inﬂuence the form of the pelvic colon, and it may itself be modiﬁed by the bowel.
As for the fate of the genito-mesenteric fold? We have seen that the upper edge may persist as the free edge of the duodeno—renal ligament. Its lower part may persist in the adult, forming the medial boundary of the retro-colic fossa, or passing from the ileum or appendix. As has been noticed in the full—ti1ne foetus which was examined, part of the fold may disappear through the mesentery fusing down over it to the posterior abdominal wall. The remainder of the fold that part attached above to the mesentery along the line of the ileac branch of the ileo-colic artery) may partly disappear through fusion with the peritoneum of the posterior abdominal wall, owing perhaps to pressure exerted upon the left surface of the fold by the pelvic colon. This is clearly demonstrated in one foetus. In this foetus the summit of the primitive omega loop of pelvic colon had rotated downwards along an arc convex towards the right. One of the extremities of the arc is at the lower end of a small, still persistent part of the genito-mesenteric fold which passes downwards from the mesentery. The other is at the genital border of the suspensory ligament of the testis (see fig.
The genito-mesenteric fold and the plica vascularis (see ﬁg. 4, C) lie each with its right surface turned and apposed to the posterior abdominal wall. 011 pushing up what has been the summit of the colon, it follows exactly the line of this are. The summit had glided downwards upon the left surface of the genito-mesenteric fold, pushing it, and with it the plica vascularis, over upon its right side. Moreover, it had caused, as a result of the pressure, the part of the genito-mesenteric fold with which it had come into contact to adhere by its right surface to the parietal peritoneum.
Moreover, on exerting slight traction on the suspensory ligament, it is noted that the peritoneum upon the posterior abdominal wall is freely movable over an area between two lines (see ﬁg. 4 (1) and (2) ). One of these leads upwards and to the right from the plica vascularis to the free edge of the persistent part of the genito—1nesenteric fold; and the other leads upwards from the plica vascularis, along the line of the spermatic vessels, as far as the root of the mesentery. These lines map out peritoneum which evidently has been derived from the genito-mesenteric fold.
This only conﬁrms the View that the fold had adhered to the posterior abdominal wall; and it is apparent that the fold had not adhered as a result of a cause such as is expressed in the “displacement” theory, but the result of the soldering together of endothelial laminae.
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