Main Functions of the Small Intestine

Digestion of Food

• The small intestine is the primary site where the digestion of food is completed. As partially digested food (chyme) enters from the stomach, it is mixed with digestive juices from the pancreas, liver (bile), and the small intestine itself. These enzymes and bile help break down proteins, fats, and carbohydrates into simpler molecules

Absorption of Nutrients

• Most nutrient absorption occurs in the small intestine. The walls are lined with fingerlike projections called villi and microvilli, which greatly increase the surface area for absorption. Nutrients such as amino acids, simple sugars, fatty acids, vitamins, and minerals are absorbed through these structures into the bloodstream or lymphatic system for use by the body

Movement of Food

• The small intestine uses coordinated muscular contractions (peristalsis) to mix food with digestive juices and move it along the digestive tract toward the large intestine

Immune Function

• The small intestine also plays a role in immune defense. It contains lymphoid tissue (such as Peyer’s patches) that helps protect the body from harmful bacteria and pathogens present in food

Hormonal and Chemical Regulation

• Cells in the small intestine produce hormones and enzymes that regulate digestion and coordinate the release of bile and pancreatic juices

Summary Table

Function| Description
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Digestion| Completes the breakdown of food with enzymes and bile
Absorption| Transfers nutrients, water, and electrolytes into the bloodstream/lymphatics
Movement| Propels food forward via muscular contractions
Immune Defense| Contains lymphoid tissue to fight pathogens
Hormonal Regulation| Produces hormones/enzymes to control digestion

In summary, the small intestine is essential for breaking down food, absorbing nearly all nutrients, moving food along the digestive tract, and supporting immune and hormonal functions