Physiology and Function Essay Example | Topics and Well Written Essays - 500 words - 2

Physiology and Function - Essay Example Peristalsis is the rhythmic segmental contraction and relaxation of the GI tract that helps in propulsion of food. Peristalsis is generally under autonomic control and is further mediated by myentric plexus located between the circular and longitudinal muscle layer. Contraction of these two muscles produces peristaltic waves, normally in a forward direction. Peristalsis plays a different role depending on the location of the GI tract. In the esophagus, it simply propels the food into the stomach. But in stomach, strong peristaltic contractions grind the food and mix it well with the acidic contents of the stomach. In the intestines the peristalsis is slow, providing sufficient time for digestion and absorption to take place (Guyton & Hall, 2000). Bile is produced and secreted by liver but is transported to gall bladder for storage. In the gall bladder it becomes concentrated and is released into the duodenum via common bile duct under the influence of cholecystokinin and vagal stimulation. Bile is composed of water, bile salts, bilirubin, cholesterol, fatty acids, lecithin and other common ions. Bile serves two important functions: assistance in fat digestions and removal of waste products. Bile does not contain any enzymes for digestion of fat but it causes emulsification of fat particles facilitating digestion and absorption in the intestinal mucosa. Bilirubin, a waste product of hemoglobin breakdown is also secreted in the feces via bile (Guyton & Hall, 2000). Saliva is secreted in the oral cavity by various glands such as parotid, submandibular, and sublingual glands. Every day these glands produce 800-1500ml of saliva. Saliva has two important components: ptyalin and mucus. Ptyalin is an amylase enzyme that helps in starch digestion, whereas mucus plays an important role in lubricating the food bolus and reducing mechanical friction. Saliva also has one important function of protecting oral cavity from invading