Peristalsis Essay

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First step is ingested food is taken into the mouth where it is torn into smaller physical parts by the teeth. The salivary enzymes; amylase and lipase are activated beginning the chemical breakdown of food. Salivary amylase divides starch into smaller glucose molecules. Physically the saliva hydrates and compacts the food for ideal propulsion through the pharynx and esophagus. Propulsion is activated voluntarily when we swallow; the tongue moves towards the hard palate of the mouth thus pushing the food into the pharynx. The constrictor muscles of the pharynx contract further; propelling the food through the larynopharynx to the larynx where the epiglottis then closes protecting the trachea from incoming food. Peristalsis continues the downward …show more content…
Food is compressed and mixed with gastric juices and enzymes such as pepsin coming from the gastric mucosa and is physically turned into chyme. Peristalis starts near the gastroesophageal sphincter causing the stomach wall to ripple. Small amounts of chyme filter through the pyloric valve via a back and forth pumping action. Depending on the size and contents of the meal the stomach empties chyme into the duodenum within four to six hours. As chyme enters the duodenum, receptors in the wall signal an inhibiting mechanism for acid and pepsin secretion. When fatty chyme enters the duodenum cholecystokinin is released, which stimulates gallbladder contraction and stimulates secretion of pancreatic juice. Bile leaves the gallbladder via the cystic duct it then moves through the bile duct to the common hepatic duct and then to the hepatopancreatic sphincter. The hepatopancreatic sphincter relaxes allowing bile to enter the duodenum. The bile salts within the bile physically break up fats into smaller sections. Pancreatic juice drains via the pancreas through the main pancreatic duct and into the hepatopancreatic sphincter where it too enters the …show more content…
Intestinal brush borders break up nucleotides into sugars and phosphate ions. Galactose, glucose, fructose, and proteins are absorbed into capillaries via facillitated diffusion while in the small intestine. Chylomicrons are absorbed in two ways; they are combined with proteins to creat lipoproteins which are then used to transport cholesterol in the blood and are absorbed into lymph. Dietary vitamins, pentose, sugars, phosphate ions, iron, calcium, and most electrolytes are absorbed in the duodenum and transported across the epithelium and enter the blood.The journey of food through the small intestine takes three to six hours. Most of the water from chyme is absorbed via osmosis while in the small intestine as well as nutrients thus changing it into fecal matter. Segmentation moves intestinal contents through the ileum toward the ileocecal valve. At the late intestinal phase segmentation ceases and duodenal mucosa releases motilin which initiates peristalsis. Ileocecal sphincter relaxes and chyme passes through into the large intestine. Valve flaps close via backward pressure as chyme goes into large

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