Absorption in the small intestine

Question 1

Villi function

Answer 1

Absorbs glucose through the walls of the small intestine

Question 2

Properties of villi

Answer 2

• About 1 mm long
• They have epithelial cells as walls which are thin
• They are surrounded by a rich capillary network
• Increase the surface area of the small intestine therefore increasing the rate of absorption.
• Able to move which increases surface area.
• Contain muscles which contract regularly to mix products of digestion (this means there is always glucose rich food next to the epithelial

Question 3

Lacteas (tiny limpatic vessels)

Answer 3

Absorbs fatty acids and glycerol

Found inside the villi.

Question 4

Thin epithelium

Answer 4

• One cell thick
• Micro villi increases surface area for absorption

Question 5

Role of active transport in absorption

Answer 5

Diffusion can at best only make both of the sides of the epithelium equal.

This means not all available glucose is absorbed; this means some glucose would pass through the body.

Thos doesn’t happen because some glucose is taken up by active transport. This means all glucose can be taken up by the blood.

Question 6

Sodium-Potassium pump

Answer 6

• Using indirect active transport, sodium is transported out of the epithelium and into the blood whilst simultaneously potassium is being transported from the blood into the epithelial. Sodium into blood 3:2 potassium into epithelial.
• Due to there now being a low concentration of sodium in the epithelium and a high concentration in the small intestine lumin, diffusion occurs. However, as the sodium diffuses into the epithelial, glucose attaches to the sodium and is also transported through. This is known as CO-TRANSPORT.
• Due to there now being a high concentration of glucose in the epithelial and low concentration in the blood, the glucose is transported to the blood through facilitated diffusion (no ATP, just change of shape of carrier protein).