DIGESTIVE SYSTEM 2 - The intestines (Absorb, Digest,...

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The intestines (Absorb, Digest, Defecate) Overview of the Digestive Process Digestion involves both a mechanical and a chemical process Both Chemical and Mechanical digestion begins at the mouth The mechanical digestion via teeth (mastication), while chemical digestion via enzymes in the saliva (lipase, amylase). In the stomach, churning action will cause food to be further digested (mechanical digestion). Additionally, the secretion of HCl will cause further chemical digestion to take place. In the Small intestine, the acidic chyme will continue to undergo chemical digestion. However, the small intestine is also a location where reabsorption occurs. The absorption occurs through the blood vessels and lymphatic vessels (for fats we absorb) At the large intestine, we are no longer talking about chyme but rather faeces. This is because, all the nutrient from our food has been absorbed by the end of the small intestine. Therefore, the content that enters the large intestine is for the most part waste product. If nutrient from our food (chyme) was not absorbed, it will be digested by the bacterial flora in the large intestine. This in turn will cause gas production.
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Small intestine: The basic plan The two main alterations in the small intestine: Villi: Finger-like projections in the small intestine’s mucosal layer Help increase surface area of the small intestine. Help increase the area where absorption occurs in the small intestine. Microvilli: The epithelial cells themselves contain microvilli to increase the surface area. These microvilli are also called the brush border due to their fuzzy appearance under a microscope. Plicae Circularis: Intense foldings that go around the circumfrance of the small intestine. As the chyme moves through the small intestine, the orientation of the plicae circularis helps put a twist to the chyme in order to get it to mix. Layers of the small intestine Mucosal Layer: The inner most layer that is further divided into three more layers: Epithelium, Lamina Propria (contains blood vessels and nerves), Muscularis mucosae (formation of folds in the intestines). Submucosa: Mucous glands sitting in this layer. The layer is supplied by the submucosal plexus of the enteric nervous system. Muscularis Layer: Contains the circular muscle and longitudinal muscle. These two muscles are controlled by the myenteric branch of the nervous system. The activities used to move substances in the small intestine. All of these layers are suspended in the cavity of our body by the mesentery, a double fold of the peritoneum. The mesentery is also the conduit for the lymphatic system, the blood vessels, and the nerves in our body.
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Small Intestine Blood Supply The blood supply to the small intestine comes mainly from the superior mesenteric artery (just inferior to the celiac trunk) The right side of the large intestine also supplied by superior mesenteric artery. The left side is supplied by the inferior mesenteric artery.
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This note was uploaded on 12/05/2011 for the course KINESIOLOG 1Y03/1YY3 taught by Professor Parises during the Spring '11 term at McMaster University.

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DIGESTIVE SYSTEM 2 - The intestines (Absorb, Digest,...

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