absorption of triglycerides

Question 1

Describe the structure of the ileum

Answer 1

Folded, villi containing capillaries and microvilli

Question 2

Explain how the ileum is adapted for absorption

Answer 2

Villi
projections that increase SA for diffusion

Many blood capillaries
maintain diffusion gradient
Increase SA for diffusion

thin walls
short diffusion pathway

Contain muscle
can move, mixes contents of ileum
maintains diffusion gradient.

Epithelial cells of villi have microvilli
increasing SA

Question 3

Explain how triglycerides are absorbed

Answer 3

Micelles (containing monoglycerides, bile salts and fatty acids) come into contact with epithelial cells lining ileum and break open.

Monoglycerides and fatty acids diffuse into epithelial cell through phospholipid bilayer (they are lipid soluble).

Monoglycerides and fatty acids reform triglycerides in the endoplasmic reticulum.

Chylomicrons (triglycerides, lipoproteins, cholesterol) formed in the Golgi apparatus

Chylomicrons leave cell by exocytosis into the lacteal (lymphatic capillary) in the villus

Chylomicrons move from the lymphatic vessels into the blood stream

Triglycerides hydrolysed by enzymes in endothelial cells of blood capillaries from where they diffuse into cells