This section of notes gives an overview of how the GIT folds from a simple rostocaudal tube into complex structures.
Embryo stage 13/14 stomach
During week 4 where the stomach will form the tube begins to dilate, forming an enlarged lumen in the tube. Dorsal border grows more rapidly than ventral, which establishes the greater curvature of the stomach. A second rotation (of 90 degrees) occurs on the longitudinal axis establishing the adult orientation of the stomach.
The greater omentum hangs like an apron over the small intestine and transverse colon. It begins attacted to the inferior end of the stomach as a fold of the dorsal mesogastrium which later fuses to form the structure we recognise anatomically. The figure below shows a lateral view of this process comparing the early second trimester arrangement with the newborn structure.
Development of the greater omentum
After the stomach the initial portion of the GIT tube is the duodenum which initially lies in the midline within the peritoneal cavity, but then (along with the attached pancreas) undergoes rotation to become a retroperitoneal structure.
The diagram below shows this rotation with spinal cord at the top, vertebral body then dorsal aorta then pertioneal wall and cavity.
Rotation of the Duodenum
About the Movie
View from left hand side of embryo facing left. Sequence spans approx 6-11 weeks of development. There is an initial 90 degree rotation followed by 2 more 90 degree rotations to give 270 degrees total. The upper GIT is shader light green, the red vessel is the superior mesenteric artery off the dorsal aorta.
Johnson LR. Functional development of the stomach. Annu Rev Physiol. 1985;47:199-215. Review.
Indiana University animation showing Development of the Stomach, Omenta and Duodenum Discussion of the development of the stomach from the foregut, the omenta development from the mesenteries, and the rotational movements of the stomach and duodenum.(approx. 2 minutes)
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