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Fig. 304. Gastrointestinal Tract and Mesenteries in a Human Embryo


The arrow points into the bursa omentalis (omental bursa, lesser sac).

The mesentery of the descending colon, or the descending mesocolon, lies in the left side of the abdominal cavity, in contact with the peritoneum of the body wall (see Fig. 304). It usually fuses with the peritoneum, and the descending colon thus becomes fixed. After the ascending colon is formed, the ascending mesocolon usually fuses with the peritoneum on the right side (see Fig. 304).

In a large percentage (possibly 25 percent) of individuals, the fusion between the peritoneum and the ascending and descending mesocolon is incomplete or wanting.

The sigmoid mesocolon bends to the left to reach the sigmoid colon, but forms no secondary attachments. It is continuous with the mesorectum which maintains its original sagittal position. A sheet of tissue the mesoappendix continuous with and resembling the mesentery, is attached to the caecum and vermiform appendix (Fig. 304). It probably represents a drawn out portion of the original common mesentery, since the caecum and appendix together are formed as an evagination from the primitive gut.

Normally the mesentery of the small intestine forms no secondary attachments, but is thrown into a number of folds which correspond to the coils of the intestine.

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

Cite this page: Hill, M.A. (2024, June 24) Embryology Bailey304.jpg. Retrieved from

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