The duodenum receives blood supply from both the coeliac trunk via the superior pancreaticoduodenal artery and from the superior mesenteric artery via the inferior pancreaticoduodenal artery due to embryonic gut derivatives from the foregut and midgut. Arterial supplyīlood supply to the small intestine arises from the celiac trunk and superior mesenteric artery which are direct branches from the abdominal aorta. These are lymphoid follicles located in the mucosa layer and extend into the submucosa layer. The ileum can be differentiated from duodenum and jejunum by the presence of Peyer’s patches. The ileum joins the first part of the large intestine, the cecum, at the ileocaecal junction.

The main function of the ileum is to absorb vitamin B12 and bile acids. The ileum is similar in structure to the jejunum and is the longest portion of the small intestine, being around 3 metres long. In addition, it does not contain Peyer’s patches which are present in the ileum only. The histology of the jejunum is similar to the duodenum, however, it does not contain Brunner’s glands. The structure of the jejunum is different to the duodenum as it is longer (approximately 2.5m) and contains plicae circulares and villi which increases the absorption of sugars, amino acids, and fatty acids (products of digestion). The jejunum is located between the duodenum and ileum. Villi of the small intestine, showing blood vessels and lymphatic vessels. This is particularly important when diagnosing incomplete rotation or malrotation on a radiological scan. The separation between the duodenum and jejunum is marked by the suspensory muscle of the duodenum (ligament of Treitz), which fixes the duodenojejunal flexure to the right crus of the diaphragm. Only the duodenum contains Brunner’s glands which are important in producing alkaline mucous to neutralise acidic chyme from the stomach and in optimising the activity of intestinal enzymes for absorption. The duodenum features a simple columnar intestinal epithelium which contains goblet cells and Paneth cells. Posterior: the ulcer may erode into blood vessels, such as the gastroduodenal artery resulting in massive haemorrhage.Anterior: the ulcer may erode into the peritoneal cavity, causing peritonitis.4Īcute complications of duodenal ulceration depend on the anatomical location of the ulcer: 1 In contrast, gastric ulceration tends to present with pain that worsens after eating. Symptoms include upper abdominal pain that is typically relieved by eating. The valvulae conniventes occur around 2.5-5 cm below the pylorus of the stomach within the duodenum and are important in increasing the surface area of absorption.ĭuodenal ulcers can develop secondary to NSAIDs or infection with Helicobacter pylori. The small intestine contains valvulae conniventes which are large mucosal circular folds that project into the lumen of the small intestine. The jejunum and ileum are suspended by mesentery which is part of the peritoneum and contains the blood vessels and nerves. The first part of the duodenum, jejunum and ileum are found intraperitoneally. The small intestine can be split into three structural parts: duodenum, jejunum, and ileum. The small intestine extends from the pylorus of the stomach to the ileocaecal junction where it meets the large intestine at the ileocaecal valve. The small intestine is the primary digestive organ of the gastrointestinal tract and has an important role in aiding digestion and absorption of chyme received from the stomach.įunctions of the small intestine include chemical digestion of proteins, lipids and carbohydrates using enzymes to break down chyme into a form that can be absorbed in the small intestine across epithelial cells via simple and facilitated diffusion, and active transport.

Pearson lumen of small intestine