Small intestine

Definition

The small intestine is a long, coiled tube where most digestion and nutrient absorption occurs. It 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. Enzymes from the pancreas and bile from the liver aid in digestion within the small intestine.
3. Villi and microvilli increase surface area for maximal nutrient absorption.
4. Peristalsis helps move chyme through the small intestine.
5. The small intestine absorbs carbohydrates, proteins, fats, vitamins, and minerals into the bloodstream.

Review Questions

• What are the three parts of the small intestine?
• Explain how villi contribute to nutrient absorption in the small intestine.
• Describe two functions of enzymes in the digestion process within the small intestine.

Related terms

duodenum: The first section of the small intestine where initial digestion occurs with help from bile and pancreatic enzymes.

jejunum: The middle section of the small intestine primarily involved in nutrient absorption.

ileum: The final section of the small intestine that absorbs vitamin B12 and bile salts before passing remaining contents to the large intestine.