L20 Duodenum PDF - Anatomy

L20 The Duodenum Small intestine is covered by a fixed part ( no mesentery ) the duodenum And a free movable part ( with mesentery ) jejunum and ileum The most proximal portion of the small intestine is the duodenum. Its name is derived from the Latin ‘duodenum digitorum’ meaning twelve fingers leng...

L20 The Duodenum Small intestine is covered by a fixed part ( no mesentery ) the duodenum And a free movable part ( with mesentery ) jejunum and ileum The most proximal portion of the small intestine is the duodenum. Its name is derived from the Latin ‘duodenum digitorum’ meaning twelve fingers length. It runs from the pylorus of the stomach to the duodenojejunal junction. The duodenum can be divided into four parts: First Part: superior Second Part: descending Third Part: inferior Fourth Part: ascending. Together these parts form a ‘C’ shape, that is around 25cm long, and which wraps around the head of the pancreas. First part (horizontal part) : 2 inches - at level L1 ( transpyloric plane ) Second part (descending) : 3 inches descends from L 1 to L3 Third part ( horizontal):4 inches L3 ( subcostal plane ) Fourth part : (Ascending ) 1 inch Ascends from L3 to L2 First part : D1 – Superior (L1) It ascends upwards from the pylorus of the stomach, and is connected to the liver by the hepatoduodenal ligament. This area is most common site of duodenal ulceration. The first inch of the superior duodenum is intraperitoneal ( movable part ) the remainder is retroperitoneal (only covered anteriorly). Second part : D2 – Descending (L1-L3) The descending portion curves inferiorly around the head of the pancreas. It lies posteriorly to the transverse colon, and anterior to the right kidney. Internally, the descending duodenum is marked by the major duodenal papilla – the opening at which bile and pancreatic secretions enter from the ampulla of Vater (hepatopancreatic ampulla). Third part : D3 –(L3) The third part of duodenum travels laterally to the left, crossing over the inferior vena cava and aorta. It is located inferiorly to the pancreas, and posteriorly to the superior mesenteric artery and vein. Fourth part: D4 – Ascending (L3-L2) After the duodenum crosses the aorta, it ascends and curves anteriorly to join the jejunum at a sharp turn known as the duodenojejunal flexure. at the duodenojejunal junction there is a slip of muscle called the suspensory muscle of the duodenum. When it contracts, it widens the angle of the flexure, and aids movement of the intestinal contents into the jejunum. Suspensory Muscle of Duodenum or Ligament of Treitz This is a fibromuscular band which suspends and supports the duodenojejunal flexure. It arises from the right crus of the diaphragm, close to the right side of the oesophagus, passes downwards behind the pancreas, and is attached to the posterior surface of the duodenojejunal flexure and the third and fourth parts of the duodenum. Normally, its contraction increases the angle of the duodenojejunal flexure. Relations of the fourth part of the duodenum Anterior : small intestine Posterior : left psoas major Arterial Supply: - ABOVE the opening (major duodenal papillae), It is supplied by the superior pancreaticoduodenal artery, - BELOW it by the inferior pancreaticoduodenal artery. Venous Drainage The veins of the duodenum drain into: - The splenic vein - Superior mesenteric vein - Portal vein Lymphatic Drainage Pancreaticoduodenal nodes - hepatic nodes - coeliac nodes - cisterna chyli. Nerve Supply Sympathetic nerves: T9 and T10 Parasympathetic nerves: Vagus Notes from recording 1. First part of the duodenum: it's first inch is intraperitoneal first part of the duodenum is closely related posteriorly to an important artery, the gastrodendoned artery, (posterior relation) 2. second part -receives the bile Secretion received the bile duct in the ampulla, in its medial wall 3. Third part has very important anterior relation (the superior me enter vera) for example; a patient with a superior mesenteric artery aneurysm (enlargement ), it will compress the anterior structure, it will compress the horizontal part of the duodenum, the patient will come complaining of nausea A problem in digestion 4. fourth part Most important thing about it is its attachment to the diaphragm by the suspensory ligament Arterial Supply, Through two arteries Superior pancreaticoduodenal from gastroduodenal , if we follow its branch we will reach celiac trunk Inferior pancreaticoduodenal from Superior Mesenteric