Absorption of Digestion Products Flashcards
What are the products that need to be absorbed as a result of digestion?
Monosaccharides, amino acids, and monoglycerides and fatty acids.
How is the ileum adapted to the function of absorbing the products of digestion?
- The wall of the ileum is folded and possesses finger like projections called villi to increase surface area.
- Thin walls lined with epithelial cells and a rich capillary network.
Where are the villi situated?
At the interface between the lumen (cavity) of the intestines and the blood and other tissues inside the body.
How do Villi help in diffusion?
- Increase the surface area for diffusion
- Thin walled, reducing diffusion distance.
What are villi able to do due to the fact that they contain muscle and so are able to move?
Maintain diffusion gradient as movement mixes the contents of the ileum, ensuring that products of digestion that are absorbed, is replaced by material rich in products of digestion.
How is a good supply of blood vessels important to the villi?
Villi are well supplied with blood vessels so that blood can carry away absorbed molecules and hence maintain a diffusion gradient.
What are microvilli?
Epithelial cells lining the villi possess microvilli which are finger like projections of the cell-surface membrane, further increasing surface area for absorption.
How are amino acids and monosaccharides absorbed?
Diffusion and co-transport
How are micelles formed?
Monoglycerides and fatty acids remain in association with the bile salts that initially emulsified the lipid droplets. The structures formed are known as micelles.
How do micelles come into contact with epithelial cells lining the villi of the ileum?
Through the movement of material within the lumen of the ileum, micelles are able to make contact with the villi.
What happens when micelles break down at the villi?
Micelles break down, releasing monoglycerides and fatty acids.
Why are the monoglycerides and fatty acids able to diffuse across the cell-surface membrane?
They are non-polar molecules so are able to diffuse across the membrane into the epithelial cells.
What happens once the monoglycerides and fatty acids have got inside the epithelial cells?
They are transported to the endoplasmic reticulum where they are recombined to form triglyceride. They continue in the Golgi apparatus, associating with cholesterol and lipoproteins to form structures called chylomicrons.
What are chylomicrons?
Special particles adapted for the transport of lipids.
How do chylomicrons move out of the cells?
Exocytosis.
