Summary
Highlights
This video focuses on the foregut, midgut, and hindgut, their components, vascular supply, and mesenteries. The foregut is unique for having two mesenteries: a ventral and a dorsal mesentery. These mesenteries connect the visceral peritoneum to the parietal peritoneum. The dorsal mesentery is known as the dorsal mesogastrium, and the ventral mesentery is the ventral mesogastrium.
A mesentery is an organ, specifically a double-layered serous membrane made of simple squamous epithelial tissue with an underlying areolar connective tissue. This structure is crucial for blood vessels, veins, nerve fibers (like splanchnic nerves), and lymphatic vessels to travel from the abdominal wall to the organs.
During development, the foregut undergoes a clockwise rotation. The ventral mesogastrium helps develop the liver, which moves to the right side, while the dorsal mesogastrium develops the spleen, moving to the left side. The ventral mesogastrium forms the lesser omentum (including ligaments like hepatogastric and falciform ligaments), and the dorsal mesogastrium becomes the greater omentum, a large apron-like structure with ligaments such as gastrocolic and gastrosplenic ligaments.
A detailed view shows the relationship between the stomach, transverse colon, and liver. The lesser omentum connects the stomach to the liver. The greater omentum hangs from the greater curvature of the stomach, doubling back and fusing with parts of the transverse colon's mesentery. The epiploic foramen, located where the hepatoduodenal ligament ends, leads into the lesser sac, an area behind the stomach.
The gut tube is divided into three main parts: foregut, midgut, and hindgut. The foregut, developing near the cranial end, is supplied by the celiac trunk. The midgut, linked to conditions like omphalocele and Meckel's diverticulum, is supplied by the superior mesenteric artery. The hindgut, at the caudal end, forming the anal canal and urogenital tract, is supplied by the inferior mesenteric artery.
Foregut organs include the spleen (supplied by the splenic artery via the celiac trunk), stomach (left gastric artery), liver and gallbladder (common hepatic artery), pancreas, and proximal half of the duodenum (gastroduodenal artery). The spleen has the gastrosplenic ligament, the stomach has the greater and lesser omentum, and the liver/gallbladder are held by the lesser omentum and falciform ligament. The tail of the pancreas has the splenorenal ligament, while the head and body are secondary retroperitoneal. Only the first part of the duodenum has a mesentery, the hepatoduodenal ligament.
Midgut organs are supplied by the superior mesenteric artery. They include the distal half (third and fourth parts) of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and proximal two-thirds of the transverse colon. The distal half of the duodenum and ascending colon are retroperitoneal (no mesentery after rotation and obliteration). The jejunum and ileum are supported by the small bowel mesentery. The cecum's mesenteric status varies, and the appendix has the mesoappendix mesentery. The proximal two-thirds of the transverse colon has the transverse mesocolon.
The hindgut is supplied by the inferior mesenteric artery and includes the distal one-third of the transverse colon, descending colon, sigmoid colon, and upper rectum up to the pectinate line. The distal one-third of the transverse colon has the transverse mesocolon. The descending colon is retroperitoneal (losing its mesentery during rotation). The sigmoid colon has the sigmoid mesocolon, and the upper rectum is retroperitoneal.