Digestion and absorption of nutrients

Question 1

Where are the arterial and venous plexuses found in the intestine

Answer 1

In the submucosal layer

Question 2

What describes the top 2/3 of the villi

Answer 2

Absorptive

Question 3

What describes the lower 1/3 of the villi

Answer 3

Fluid secretory

Question 4

Describe the digestion of starch into the blood stream

Answer 4

Starch is hydrolysed by a-amylase to glucose, maltose which is converted to glucose then by maltase. This is brought into the cells via Na+ co transport, then it enters the blood

Question 5

Describe the physiology of the absorption of monosaccharides in intestinal epithelial cells

Answer 5

GLUT5 transporters deal with fructose

Na+:glu co transporter brings in glu, which then passes into interstitial space via GLUT2 transporters.
Na+:K+ ATPase in basolateral membrane removes Na+ from cell creating a conc gradient which drives process

Question 6

What type of transport is used to absorb amino acids in the intestines?

Answer 6

Na+ co transport

Question 7

What type of transport is used to absorb di and tripeptides in the intestines?

Answer 7

H+ co transport

Question 8

What is Hartnup disease

Answer 8

Phe not absorbed on its own only as a peptide

Question 9

What is Cystinuria

Answer 9

Arg no absorbed on its own only as a peptide

Question 10

How is vit K produced and absorbed

Answer 10

by intestinal bacteria + taken up in newly synthesised chylomicrons going to the lacteals

Question 11

How are vit A + E absorbed

Answer 11

Taken up in newly synthesised chylomicrons going into the lacteals

Question 12

What is the other name for vit B12

Answer 12

Cobalamin

Question 13

Describe the physiology of Vit A+E+K absorbtion into intestinal epithelial cells

Answer 13

Na+ co transport in apical membrane. Then Na:K ATPase creates conc gradient that drives process.
Vit then diffuses across basolateral membrane

Question 14

Describe the physiology of B12 absorption

Answer 14

CBL modified in stomach and IF (Intrinsic factor, released from parietal cells) forms complex.
Ileal enterocyte absorbs complex.
IF absorbed by enterocyte

Question 15

Describe the physiology of Ca2+ across intestinal epithelium

Answer 15

Ca2+ diffuses into cell and binds with calbindin which carries it to the next protein.

Ca2+:H+ and Ca:Na exchangers in basolateral membrane removes Ca2+ from cell.

There is also paracellular movt of Ca