Published on 25 Aug 2011 | over 5 years ago
In digestion, food is changed by the organs into a sizable form to be absorbed by the body. Food in the mouth is mixed with saliva; saliva begins to dissolve the food as the teeth grind and cut it. Food is forced back into the throat, pharynx, by the tongue. Food in the pharynx stimulates the swallowing reflex. The larynx is pulled upward to meet the epiglottis and seal off the trachea. Food goes from the larynx to the esophagus. Food moves down the esophagus by peristalsis. The peristaltic wave reaches the esophageal sphincter and food enters the stomach. The unique muscular structure of the stomach breaks up the food into small pieces called "chyme". Chyme exists through the pyloric sphincter into the duodenum of the small intestine. The major portion of absorption and digestion occurs in the small intestine. The mucosa secretes enzymes that supplement the digestive enzymes of the pancreas and liver. This completes the chemical process of digestion.
The walls are covered with villi, where nutrient absorption takes place. The structure of each villus contains a capillary and lacteal to pick up the digestive nutrients. The nutrients are transported by the blood to all the cells of the body. The undigested food reaches into the ileo-cecal valve and enters the large intestine or colon. The colon absorbs water, manufactures vitamins, produces mucous, and form and expels feces. Mass peristalsis pushes the feces into the rectum which stimulates the defecation reflex.