Digestive System
Digestive System

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- embryology of the gut tube - trilaminar embryo fol ds on itself, creating gut tube, lined by endodermal epithelium and surrounded by splanchnic mesoderm - ‘enteron’ is the gut tube (alimentary canal) from pharynx to rectum, including ventral yolk sac - tra chea/lung buds are ventral outgrowth of enteron at laryngeal groove ( see respiratory embryology ) - gastrointestinal embryology, including the pharyngeal pouches [also called branchial (gill) pouches] - anatomic de finitions of foregut, midgut, and hindgut are based on vascular supply - foregut = esophagus, stomach, and duodenum = supplied by celiac artery - esophageal exception: after embryonic stages, blood supply to the intra - t horacic esophagus is from small branches directly from the descending aorta - foregut has dorsal and ventral mesenteries - ventral mesentery of esophagus is mesentery of heart (dorsal mesocardi um) - dorsal and ventral mesenteries of esophagus disintegrate as it elongates - dorsal mesentery of caudal foregut (future stomach), containing celiac artery, also contains dorsal pancreatic divert iculum and ‘anlage’ (originating tissue) of spleen - ventral mesentery of caudal foregut contains hepatopancreatic diverticulum which becomes ventral pancreas and (as it invades septum transversum) liver - midgut = small intestine and first part of large intestine (including most of transverse colon) = supplied by superior mesenteric artery - hindgut = descending colon, sigmoid colon, and rectum = supplied by the inferior mesenteric artery - midgut and hindgut only have dorsal mesenteries, containing branches of the superior and inferior mesenteric arteries, carrying vascu lar supply from aorta - gut rotations - as viewed from anteriorly, the caudal foregut (stomach and duodenum) rotates 90° clockwise and the midgut rotates 270° counterclockwise © neural tube ▲ notochord ▲ ▲Rathke’s pouch ▲Rathke’s pouch