Duodenum (duodenum) - the initial section of the small intestine, located on the back wall of the abdominal cavity. The duodenum starts from the pylorus, ends with a duodenum-jejunal bend located at the left edge of the II lumbar vertebra. In typical cases, the duodenum is shaped like a horseshoe around the head of the pancreas. In the duodenum, the upper, descending, horizontal and ascending parts are distinguished.
The upper part (pars superior), or the bulb, is the shortest (3-6 cm) and wide (up to 4 cm), from the pylorus to the right and back and forms the upper bend of the duodenum. Almost 3/4 of the circumference of this part of the intestine is covered by the peritoneum. With a moderately or strongly filled stomach, the upper part is almost sagittal, with empty - more transversely. Its upper surface borders on the back of the square lobe of the liver, then crosses the right side of its own hepatic artery and the common hepatic duct. Below, the upper part of the duodenum comes into contact with the upper part of the head of the pancreas and the transverse colon. Behind the upper part in the thickness of the hepatic-duodenum ligament are the common hepatic duct (right), the hepatic artery (left), the portal vein (behind and in between).
The descending part (pars descendens) starts from the upper bend of the duodenum at level I of the lumbar vertebra, descends down along the right side of the spine. The descending part ends at level III of the lumbar vertebra by a sharp turn to the left with the formation of a lower bend of the duodenum. The length of the descending part is 8-10 cm. Behind it are the gates of the right kidney, the upper part of the ureter. Medially, the posterior surface of the descending part borders on the inferior vena cava, and in the region of the transition of the upper part to the descending part of the gut - with the right adrenal. In the front, the descending part is covered with the peritoneum, intersecting with the root of the mesentery of the transverse colon. On the left, the descending part borders on the head of the pancreas and closely fuses with its capsule. Between the descending part and the head of the pancreas are the terminal part of the common bile duct and anastomosing the upper and lower pancreatic-duodenal arteries.
The horizontal part (pars horizontalis) starts from the lower bend of the duodenum, goes horizontally to the left at level III of the lumbar vertebra, then turns upward and passes to the ascending part at the level of intersection with the superior mesenteric artery and vein. Behind the horizontal part are the lower hollow vein (right) and the aorta (left). The anterior surface of the horizontal part is covered by the peritoneum, the loops of the small intestine adjoin it.
The ascending part (pars ascendens) begins at the site of the exit of the superior mesenteric artery and vein from under the lower edge of the pancreas to the anterior surface of the duodenum. The ascending part ends at the upper edge of the body II of the lumbar vertebra by a sharp bowing of the intestine down, forward and to the left with a duodenum-jejunal flexure (flexura duodenojejunalis). The bend is fixed to the diaphragm by a muscle and a ligament suspending the duodenum (m. Et lig.suspensorii duodeni). Behind the ascending part is the aorta, and in front - the parietal peritoneum.
Innervation: the parasympathetic nerve fibers from the vagus nerves come to the duodenum, and the sympathetic nerves come from the gastric, hepatic and upper mesenteric plexuses. The jejunum and the iliac are innervated by the fibers of the vagus nerves, and also by the superior mesenteric plexus.
Blood supply: the duodenum is supplied with the anterior and posterior pancreatic-duodenal arteries (from the gastro-duodenum), the inferior pancreatic-duodenal artery (from the superior mesenteric artery); jejunum and iliac - jejunal and ileo-intestinal arteries (from the superior mesenteric artery). Venous outflow occurs on the same veins in the portal vein.
Outflow of lymph: from the duodenum to the pancreas-duodenum, upper mesenteric, celiac, lumbar lymph nodes, from the jejunum and iliac - mesenteric and ileo-colon (from the terminal part of the ileum) lymph nodes.
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