Small intestine

by Jason Wasserman MD PhD FRCPC
April 18, 2022


What is the small intestine?

The small intestine is a part of the digestive system. Another name for the small intestine is the small bowel. The small intestine is a long tube that starts at the stomach and ends at the colon. It is divided into three parts: duodenum, jejunum, and ileum. The duodenum is the shortest part of the small intestine. It connects to the stomach on the right side of the body just below the ribs.

What does the small intestine do?

Food that we eat enters the stomach where it is mixed and broken down by strong acids made by cells inside the stomach. When this is complete, the digested food moves into the small intestine. The purpose of the small intestine is to absorb nutrients from the food and transport those nutrients into the body.

What types of cells are normally found in the small intestine?

The inside of the small intestine is lined by epithelial cells that are specially designed to absorb nutrients from the food we eat. These specialized cells form a barrier called an epithelium. Below the epithelium is a thin layer of tissue called the lamina propria. This tissue contains many small blood vessels which support the epithelial cells. Mucosa is a word pathologists use to describe the epithelium and lamina propria together. The mucosa in the small intestine grows in a way that creates long finger-like projections of tissue called villi. These villi allow the small bowel to have a large surface area in a relatively small space.

duodenum normal

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