Absorption of Digested Food in the Small Intestine
The small intestine is crucial for absorbing digested food. It has specialized structures that enhance absorption:
- Villi: These are tiny, finger-like projections that increase the surface area for absorption.
- Microvilli: Even smaller projections on the villi further increase the surface area.
- Capillaries: Each villus contains blood capillaries that transport absorbed nutrients into the bloodstream.
Digested food, primarily carbohydrates, proteins, and fats, is absorbed through the walls of the small intestine. Nutrients pass through the epithelial cells of the villi via:
- Diffusion: Small molecules like glucose and amino acids move from high to low concentration.
- Active Transport: Some nutrients, like certain ions, require energy to move against their concentration gradient.
Once absorbed, nutrients enter the bloodstream and are transported to various body cells for energy, growth, and repair. The efficiency of absorption is enhanced by the large surface area provided by the villi and microvilli, ensuring that the body receives adequate nutrition from food.
Key points to remember
- The small intestine has villi that increase surface area.
- Microvilli further enhance absorption efficiency.
- Nutrients are absorbed through diffusion and active transport.
- Capillaries in villi transport absorbed nutrients to the bloodstream.
- Absorption ensures nutrients reach body cells for various functions.
Worked example
Explain how digested food is absorbed in the small intestine.
- The small intestine absorbs digested food through villi and microvilli.
- Nutrients enter via diffusion and active transport into capillaries.