What Does The Small Intestine Do?

Learn the nuances of what the small intestine does. The process by which your small intestine aborbs your food is amazing.

Before the body can use the soluble products formed during digestive action, the nutrients must be absorbed through the lining of the digestive tract. Even though water and small amounts of simple sugars pass through the mucosa of the stomach into the blood stream, most of the absorption takes place in the small intestine. The absorptive area of this section of the digestive passage is increased an estimated 600 fold by the villi, which are fingerlike projections in the lining of the small intestine. Each villi contains a lymph vessel surrounded by a network of capillaries. The nutrients absorbed into the lymph vessel pass into the lymphatic system, and those absorbed by the capillaries empty into the portal vein and are carried direction to the liver. The lymph vessels are the "connecting passageways" in the body, between the blood and tissues, by which food material and oxygen are brought to the individual cells.

The stomach produces gastric juice and mixes it with food. Gastric juice contains enzymes that begin the digestion of proteins. Proteins are the only substances digested in the stomach. However, they are only partially digested there. The food is churned and mixed with stomach fluids until a thick paste called chyme is produced. The chyme passes through the stomach into the small intestine.

Enzymes from the pancreas and intestinal glands continue the breakdown of proteins. They also change starch into simple sugars and fats into fatty acids. The body digests and absorbs fat with the help of bile, which is a thick yellow green fluid released by the liver. Bile is stored in the gallbladder and released into the duodenum.



The small intestine may be 7.5 to 9 meters in length. Food is moved along by peristalsis. Digestion is completed in the small intestine.

Most chemical digestion and absorption of food occurs in the small intestine. The small intestine is a long, coiled organ about one inch in diameter. The stomach connects with the duodenum, the first part of the small intestine. The duodenum is about one foot long and is shaped like the letter C. The major digestion begins here. The pancreas and intestinal glands play important roles in completing the breakdown of foods. The pancreas is a long, soft gland lying behind the stomach that secretes digestive enzymes into the duodenum. The intestinal glands are tiny organs found in the lining of the small intestines. They release digestive enzymes and mucus.

Nutrients are absorbed throughout the small intestine. The villi are very tiny fingerlike projections lining the walls of the small intestine. The surface are of the small intestine is increased by many projections. The increased surface area will allow the small intestine to absorb most of the nutrients of the body. There are blood vessels and vessels contained a fluid called lymph inside the villi. Fat-soluble vitamins and fatty acids are absorbed into the lymph system. Glucose, amino acids, water-soluble vitamins, and minerals are absorbed into the blood vessels. the blood and lymph then carry the completely digested food throughout the body.

Enzymes from the pancreas and intestional glands continue the breakdown of proteins. They also change starch into simple sugars and fats into fatty acids. The body digests and absorbs fat with the help of bile, which is a thick yellow green fluid released by the liver. Bile is stored in the gallbladder and released into the duodenum.

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