6.10 absorption of the products of digestion

Question 1

describe the structure of the ileum

Answer 1

• wall is folded into 1mm projections (villi) with thin walls and a network of capillaries
• they also extend into microvilli.
• villi increase the SA, increasing the rate of absorption.
• villi are found between the lumen of the intestine and the body’s internal tissue.

Question 2

How do villi increase the efficiency of absorption?

Answer 2

• increase SA for diffusion
• thin walls reducing diffusion distance
• muscles mean they can move, moving products so once it is absorbed, new material can replace it.
• well supplied with blood vessels to maintain diffusion gradient
• microvilli on surface further increase SA

Question 3

Describe the absorption of triglycerides

Answer 3

1) monoglycerides and fatty acids remain in association with bile salts in micelles
2) micelles contact villi epithelium and hydrolyse into monoglycerides and fatty acids
3) as they are non-polar they easily diffuse into epithelial cells
4) they are transported into the endoplasmic reticulum and are recombined into triglycerides.
5) passed into the golgi apparatus, where they associat with cholesteral and lipoproteins to form chlymicrons
6) chlyomicrons move by exocytosis out of the epithelial cells into lymphatic capillaries fount in the centre of each villus
7) they pass into blood where they’re hydrolysed in endothelial cells of blood capillaries
8) they diffuse into cells.

Question 4

How are amino acids and monoglycerides absorbed

Answer 4

diffusion and co transport.