Paper - On the position of the vitelline arteries in human embryos
|Embryology - 2 Jun 2020 Expand to Translate|
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Papez JW. and Lewis FT. On the position of the vitelline arteries in human embryos. (1917) Anat. Rec, 11: 392-394.
| This 1917 paper presented by Papez and Lewis at the 33rd Meeting of the American Association of Anatomists in New York (Dec 27-29, 2016). Describes the vitelline arteries in the human embryo.
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On the Position of the Vitelline Arteries in Human Embryos
By JW. Papez and Frederic T. Lewis
This paper is a continuation of the study of the mesenterium commune reported at the last meeting of the association. The relation of the mesenteric artery to the rotation of the intestine can now be more fully considered. Broman, in 1914, declared that the proximal part of the definitive vitelline artery arises, as is well known, by the fusion of a pair of ventral aortic branches. Evans (’12) reviewed the evidence that instead of fusing, either the right or left members of an original pair may shift to the median line and become the persistent vessel, and he concluded that “the question is an open one.” The formation of the very short median stem which by great elongation becomes the superior mesenteric artery, requires an anastomosis or partial fusion between the right and left vessels, but not necessarily a complete fusion. Sections of the successive median roots of the mesenteric artery in a single embryo seem to show that sometimes the vessels fuse from the aorta outward, and sometimes one member of a pair enlarges as its mate becomes obliterated. After the short median vitelline trunks have been formed and have anastomosed antero-posteriorly to make the final superior mesenteric artery, that vessel increases rapidly in length and caliber. In an embryo of 4.6 mm its trunk divides into several branches which encircle the intestine and re-unite as they proceed to the yolk-sac. The vessels crossing the intestine are remnants of the considerable row of vitelline arteries of earlier stages, and by persistence on one or the other side, they would cause the mesenteric artery to cross on the left or right of the ileum respectively. Usually the persistent vessel crosses the intestinal tube on the right side as seen in a 7.5 mm embryo.
At 10 mm the intestinal loop has dropped downward over the artery, which then appears below the ileum; and at 14.5 and 22.8 mm. the artery is seen on the left side of the small intestine. Nevertheless it is morphologically on the right side, as is made apparent by undoing the effects of intestinal rotation. In all these stages it does not become free from the mesentery until it is about to cross the intestinal tube. (The same is true of the vitelline vein, but since the latter crosses the duodenum, it has a long course as a free vessel within the abdominal cavity).
In an embryo of 44.3 mm the intestines are entirely within the abdomen. The vitelline artery has now become free from the mesentery for a considerable distance before reaching the ileum. Thus it comes out from the, left side of the mesentery as a strand which extends to the umbilicus. Owing to further rotation, the intestinal tube seems to encircle it completely; but again by undoing the intestinal rotation the artery is found to be morphologically on the right side. An unusual case in which the left half of the peri-intestinal arterial ring persisted, so that the vitelline artery crossed the intestine on the left, was found in an embryo of 42 mm. This shows conclusively that the artery may persist on either side of the intestine without modifying the direction of the intestinal rotation, and the same is true of the vitelline vein, which in an abnormal embryo modelled by Begg crossed the duodenum on the right. Usually the vein persists on the left side of the tube and the artery on the right side, but these are not essential factors in directing the intestinal rotation.
The vitelline artery, as found by Dexter in the cat ('00) anchors the ileum to the umbilical hernial sac so that the jejunum re-enters the abdomen first and the ileum last of all, stretching the artery to a filamentous strand. This order of return has been confirmed by Broman for the seal, and is probably applicable to man. After the arterial strand ruptures (which usually takes place in embryos somewhat older than those studied, though the strand may exceptionally persist until birth, and rarely through adult life) the place of its attachment to the mesentery may be indicated by an appendage of the mesentery, which Broman finds invariably in seals and names the appendix meso-ilei. According to Fitz, who made an important clinical study of omphalo-mesenteric remains in man (’84), Ruge described such appendages as frequent, but Fitz admits that he hirnsclf sought for them with only indifferent success. The models of the 42 and 44 mm embryos indicate the position, well on the side of the mesentery, where such appendages may be expected, and it seems quite probable that they have been frequently overlooked.
Cite this page: Hill, M.A. (2020, June 2) Embryology Paper - On the position of the vitelline arteries in human embryos. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_On_the_position_of_the_vitelline_arteries_in_human_embryos
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