Small intestine

Definition

The small intestine is a long, coiled tube where most digestion and absorption of nutrients occur. It is divided into three sections: 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. The inner surface of the small intestine has villi and microvilli to increase surface area for absorption.
3. Enzymes from the pancreas and bile from the liver aid in digestion within the small intestine.
4. Nutrient absorption primarily occurs in the jejunum and ileum sections.
5. The duodenum receives chyme from the stomach and begins the process of nutrient breakdown.

Review Questions

• What are the three sections of the small intestine?
• How do villi and microvilli contribute to nutrient absorption?
• Which organs provide enzymes and bile that aid digestion in the small intestine?

Related terms

duodenum:

The first part of the small intestine where initial digestion takes place with digestive juices.

jejunum:

The middle section of the small intestine primarily responsible for nutrient absorption.

ileum:

The final section of the small intestine where absorption continues before passing contents to the large intestine.