Small intestine

Definition

The small intestine is a long, coiled tube where most digestion and nutrient absorption occurs. It connects the stomach to the large intestine and consists of three parts: the duodenum, jejunum, and ileum.

5 Must Know Facts For Your Next Test

1. The small intestine is approximately 20 feet long in adults.
2. It has a highly folded inner surface with villi and microvilli that increase surface area for absorption.
3. The duodenum receives chyme from the stomach and digestive enzymes from the pancreas and bile from the liver.
4. Most nutrient absorption occurs in the jejunum.
5. The ileum absorbs vitamin B12, bile salts, and any remaining nutrients before passing indigestible food to the large intestine.

Review Questions

• What are the three main sections of the small intestine?
• How does the structure of the small intestine aid in nutrient absorption?
• What roles do the duodenum, jejunum, and ileum play in digestion?

Related terms

duodenum: The first section of the small intestine where initial digestion occurs.

jejunum: The middle section of the small intestine where most nutrient absorption takes place.

ileum: The last section of the small intestine responsible for absorbing vitamin B12 and bile salts.