Biology 3.9 Absorption in the Small Intestine

Villi and microvilli

Glucose absorbed through walls of small intestine.

Walls are folded, possess finger-like projections called villi.

Small intestines have thin walls, lined with epithelial cells, otherside - rich network of blood capillaries.

Villi = increase surface area therefore accelerate rate of absorption.

Part of specialised exchange surface between lumen of small intestine and blood vessels, adapted for absorption of production of digestion.

• Increase surface area for diffusion.
• V. thin walled = reduced diffusion path.
• Able to move = maintain diffusion gradient.
• Well supplied with blood vessels = maintain diffusion gradient.

Epithelial cells possess microvilli = fingerlike projections on cell surface membrane - collectively brush border.

Role of diffusion in absorption

Carbohydrates being digested continuously = greater concentratino of glucose within lumen of small intestine than in blood = concentration gradient.

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