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The foregut arises from the endoderm, developing from the folding primitive gut, and is developmentally distinct from the midgut and hindgut. Although the term “foregut” is typically used in reference to the anterior section of the primitive gut, components of the adult gut can also be described with this designation.
Initially the foregut, midgut, and hindgut are in extensive contact with the mesenchyme of the posterior abdominal wall. By the fifth week, the connecting tissue bridge has narrowed, and the caudal part of the foregut, the midgut, and a major part of the hindgut are suspended from the abdominal wall by the dorsal mesentery, which extends from ...
Hindgut fermenters generally have a cecum and large intestine that are much larger and more complex than those of a foregut or midgut fermenter. [5] Research on small cecum fermenters such as flying squirrels, rabbits and lemurs has revealed these mammals to have a GI tract about 10-13 times the length of their body. [6]
During fetal life, the primitive gut is gradually patterned into three segments: foregut, midgut, and hindgut. Although these terms are often used in reference to segments of the primitive gut, they are also used regularly to describe regions of the definitive gut as well.
The hindgut (or epigaster) is the posterior part of the alimentary canal. In mammals, it includes the distal one third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and up to the ano-rectal junction. In zoology, the term hindgut refers also to the cecum and ascending colon.
The gastrointestinal tract and associated dorsal mesentery are subdivided into foregut, midgut, and hindgut regions based on the respective blood supply. The foregut is supplied by the celiac trunk, the midgut is supplied by the superior mesenteric artery (SMA), and the hindgut is supplied by the inferior mesenteric artery (IMA).
Arterial supply to the midgut is from the superior mesenteric artery, an unpaired branch of the aorta.Venous drainage is to the portal venous system. Lymph from the midgut drains to prevertebral superior mesenteric nodes located at the origin of the superior mesenteric artery from the aorta.
The buccopharyngeal membrane is created in the foregut and is perforated during the fourth week of human development, creating the primitive mouth, whereas the cloacal membrane is created in the hindgut and is perforated during the eighth week of human development, creating the primitive anus after the mouth opening has already been created. [5]