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Fig. 263. Gastrointestinal tract and mesenteries of a human embryo of 6 weeks

Toldt.

The intestine as a whole is suspended in the abdominal cavity by the dorsal mesentery which is attached to the dorsal body wall and which is continuous with the dorsal mesogastrium. A ventral mesentery, continuous with the ventral mesogastrium, is present only at the cephalic end of the duodenum (Fig. 263).

The further development of the intestine, apart from histogenesis, consists very largely of the formation of loops and coils, due to an enormous increase in the length of the tube. The abdominal cavity at the same time enlarges to accommodate the increased bulk. As the stomach changes its position (p. 305) , the duodenum comes to lie obliquely across the body and forms a curve with the concavity directed dorsally (Fig. 263). The rest of the intestine forms a loop which extends ventrally and caudally as far as the umbilicus. The arms of the loop are almost parallel and the cephalic arm lies a little to the left of the caudal. The apex of the loop extends into the umbilical ccelom and is attached to the yolk stalk. From the dorsal end of the caudal arm the intestine extends directly to the caudal end of the body (Fig. 263).

Soon after the loop is formed a small evagination appears on its caudal arm, not far from the apex. This is the anlage of the cecum and marks the boundary between the small and large intestine (Fig. 263). At this stage, therefore, all the great divisions of the intestinal tract are distinguishable, viz. : the duodenum with the ducts of the liver and pancreas; the mesenterial small intestine with the yolk stalk; and the colon extending from the caecum to the caudal end. There are, however, practically no differences between the regions, either in structure or in size.


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Reference

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.



Cite this page: Hill, M.A. (2024, March 4) Embryology Bailey263.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Bailey263.jpg

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