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Small Intestine

The small intestine is an organ inside of your body that is part of the digestive tract, between the stomach and the large intestine. The stomach empties its contents slowly into the small intestine. The small intestine empties into the large intestine. The large intestine starts at the end of the small intestine. The word bowel can refer to the large and small intestines.

The small intestine measures about 22 feet long and about 1 and a half to 2 inches around, and includes the duodenum, jejunum, and ileum.

• The duodenum is the first part of the small intestine, right after your stomach
• The jejunum is the middle section of the small intestine between the duodenum and ileum
• The ileum is the lower end of the small intestine.

Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine where the nutrients are absorbed into your blood. Leftover water and solid waste then move down into your large intestine, where most of the water is absorbed back into the blood. Solid waste leaves the body out of the anus as a bowel movement.

The liver, gallbladder, and pancreas are accessory organs of the digestive system that are closely associated with the small intestine.

Bile is excreted into the small intestine, where it helps digest fat. Bile is a yellowish-green fluid made by the liver and stored in the gallbladder.

An enzyme in the lining of the small intestine digests table sugar into glucose and fructose, each of which can be absorbed from the intestinal cavity into the blood. Milk contains another type of sugar, lactose, which is changed into absorbable molecules by an enzyme called lactase, also found in the intestinal lining.

Foods that are not easily broken down in the small intestine and are most likely to produce gas in the colon (where bacteria ferment them and gas is produced as a by-product) are those high in fiber, starches or milk sugar (lactose).

Beans pass through the small intestine and arrive in the large intestine undigested which causes flatulence (gas) to occur. Beans contain more indigestible carbohydrates than most foods.

Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.

The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa (tiny glands that produce juices to help digest food) of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system, where they stimulate digestive juices and cause organ movement.

People who have celiac disease (pronounced - SEL-ee-ak) cannot tolerate a protein called gluten, found in wheat, rye, and barley. Some people also have trouble with oats. Celiac disease is a digestive disease that damages the small intestine and interferes with absorption of nutrients from food. Tiny, fingerlike protrusions lining the small intestine, called villi, are damaged or destroyed. Villi normally allow nutrients from food to be absorbed through the walls of the small intestine into the bloodstream. Without healthy villi, a person becomes malnourished, regardless of the quantity of food eaten.

Crohn's Disease causes inflammation of parts of the digestive tract, but it most often affects a part of the small intestine called the ileum, the last part of the small intestine.

Ileostomy (pronounced - il-ee-AW-stuh-mee) is surgery to remove the entire large intestine and connect the bottom of the small intestine (ileum) to a hole in the abdomen. This hole in the abdomen is called a stoma. Stool leaves the body through the stoma, instead of through the anus, and goes into a bag attached to the skin around the stoma. This bag must be emptied several times a day.

Infection of the small intestine and the large intestine is called enterocolitis. It can happen before or after surgery to treat Hirschsprung Disease

When a person with primary biliary cirrhosis has jaundice, the small intestine cannot easily absorb fats and fat-soluble vitamins. Maldigestion may result in diarrhea and fatty stools and can lead to weight loss in the late stages of the disease.

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References:
National Digestive Diseases Information Clearinghouse (NDDIC)
April 2008
digestive.niddk.nih.gov

The information discussed above is a general overview and does not include all the facts, or include everything there is to know about any medicine and/or products mentioned. Do not use any medicine and/or products without first talking to your doctor. Possible side effects of medications, other than those listed, may occur. Other brand names or generic forms of this medicine may also be available. If you have questions or concerns, or want more information, your doctor or pharmacist has the complete prescribing information about this medicine and possible drug interactions.