3.9 Absorption In The Small Intestine Flashcards
How long is a villi?
1mm
How is glucose absorbed into the body?
Through the walls of the small intestine
Describe the walls of the villi…
Thin and lined with epithelial cells on the other side of which is a rich network of blood capillaries.
What is the main purpose of villi in the small intestine?
They considerable increase the surface area of the small intestine and accelerated the rate of absorption.
Where a villi situated?
At the interface between the lumen of the intestines and the blood and other tissues inside the body.
List four properties of villi which increase efficiency in absorption.
They increase surface area for absorption
They have very thin walls making the diffusion pathway shorter
They are able to move and so help to maintain a diffusion gradient (mixes contents of small intestine - as glucose is absorbed, new glucose replaces it.)
They are well supplied with blood vessels so that blood can carry away absorbed molecules and hence maintain a diffusion gradient.
What are microvilli collectively named?
A ‘brush border’ because under the light microscope they look like a brush.
How long are microvilli?
0.6 micrometers
As carbohydrates are being digested continuously, there is normally a greater concentration of glucose…
Within the small intestine than in the blood.
What are the four stages in glucose absorption in the epithelial cells of the small intestine? (Sodium)
- Sodium ions go out of the cells by sodium-potassium pump and into the blood (active transport)(protein carrier)
- Now a higher conc of sodium ions in the lumen then in the epithelial cells
- Sodium ions diffuse into cells with glucose molecules (co-transport) (carrier protein) (passive transport)
- Glucose passes into the blood plasma by facilitated diffusion using another carrier protein.
