Small intestine and secretion

Anatori Sealife Comments 0 11th April 2019
The small intestine is a long, tubular structure

The small intestine is approximately twenty-three feet or seven meters in length. It begins at the pyloric valve of the stomach, ends at the ileocecal valve between the ilium and cecum, and has an average diameter of about one inch. Millions of fingerlike projections, called villi, increase tremendously the inner absorptive surface area, where they are present throughout. Likewise, do the plicae circulares which are deep circular folds in the mucosa of the intestine.

Peristalsis is a slow, wavelike muscular contraction that pushes chyme through the tube. Rhythmic segmentation involves circular muscle contractions at alternate points around the chyme. Thus, it helps mix the chyme and the intestinal juices. Pendular movement involves the alternate contraction of circular and longitudinal muscles in the intestine; this also increases the mixing of chyme and intestinal juices.

Small intestine secretion

Most of the digestion and a majority of the absorption occurs in the small intestine. The pancreatic, liver and intestinal secretions neutralize acid chyme from the stomach in the intestine. However, it occurs such that the pH of the intestine is continually increasing from the duodenum to the ileocecal valve.

Other hormones which are indirectly related to digestive activities are secretin, pancreatin, enterocrinin, and cholecystokinin. As a result, chyme entering the small intestine stimulates the secretion of these hormones.

Secretin and pancreatin stimulate the secretion of pancreatic juices, enterocrinin stimulates the secretion of digestive enzymes from the small intestine, and cholecystokinin stimulates both the contraction of the gallbladder and the relaxation of the sphincter of Oddi. This sphincter controls the flow of bile and pancreatic juices from the common bile duct into the duodenum.


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Trypsin

The exocrine secretions of the small intestine are digestive in nature. Enterokinase activates pancreatic trypsinogen (inactive trypsin) so that protein digestion may proceed. Meanwhile, the final break down of amino acid chains involve Trypsin. Weak amylase aids in the break down of complex sugars to disaccharides. Maltase breaks down maltose into glucose.

Sucrase breaks down lactose into glucose and galactose. Brunner’s Gland releases a final intestinal secretion. It is a mucous secretion which protects the intestinal lining from the acid chyme. Besides their digestive and protective qualities, the intestinal juices aid in the transport of undigested material.