Small Intestine - vessels that supply the intestinal wall....

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Digestive System Small Intestine * Most digestion occurs here, therefore, it is specifically designed for absorption. * Long length provide a large surface area * modification of the wall further increases surface area (plicae [circulare folds] , villi, and microvilli). * Average dimension is 1 inch in diameter and 21 feet in length ( in cadaver and 10 ft in living person). Gross Anatomy The small intestine is divided into three parts: one immobile and two mobile. * Duodenum- * the first portion and the shortest part of the SI, about 10 inches long. * It has a “C” shaped curve that begins at the pyloric spinchter of the stomach and merges with the jejunum. * It lies behind the parietal peritoneum and is the most fixed portion of the SI. Gross Anatomy(cont.) * The jejunum and ileum are the remaining mobile portions of the SI that are suspended from the posterior abdominal wall by a double-layered fold of peritoneum, called mesentary . This supporting tissue contain the blood vessels, nerves, and lymphatic
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Unformatted text preview: vessels that supply the intestinal wall. * Jejunum- approximately 2/5 (3 ft.) of the remainder of the SI. * Ileum- makes up the remaining 6-7 ft. of the SI. The terminal portion of the ileum empties into the medial side of the cecum (first portion of the large intestine) through the ileocecal valve. Micro Anatomy * The wall of the SI is composed of the same 4 layers that make up most of the GI tract. * There are special features for its digestive and absorptive functions:villi and microvilli. * villi- finger like fold of the mucosa that are more numerous in the duodenum and proximal part of the jejunum. * they are 1mm long and give the intestine its velvety appearance. * Villi vastly increase the surface area of the epithelium available for absorption and digestion. * Each villi has a connective tissue network containing blood vessels, nerves, and a lacteal (a lymphatic vessel that absorbs fat)...
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