Lecture 31

Question 1

What is the function of crypt cells?

Answer 1

sensory function

Question 2

What is the function of villous cells?

Answer 2

absorptive function

Question 3

Describe the gap junctions that are present within normal mucosal cells and describe the transport that occurs across them:

Answer 3

Normally the mucosa cells are bound by tight junction. Absorption can occur either passively or actively through the cells or via the lateral intracellular spaces

Question 4

What is the biggest step up in terms of increasing mucosal surface area?

Answer 4

Going from villi to microvilli is a significant step up in terms of mucosal surface area

Question 5

What are the two enzymes within the digestive system that are responsible for the degrading of starch and glycogen to maltose?

Answer 5

salivary amylase and pancreatic amylase

Question 6

Name the following substances in the diagram below

Answer 6

1. glucose x 2
2. glucose and fructose
3. glucose and galactose
4. maltase
5. sucrase
6. lactase

Question 7

How are glucose and galactose moved across the apical membrane?

Answer 7

glucose and galactos are moved across the apical membrane via secondary active transport with sodium (SGLT1)

Question 8

How is fructose moved across the apical membrane?

Answer 8

GLUT5 transporter

Question 9

What enzymes are responsible for hydrolysis of peptides?

Answer 9

gastic pepsin and pancreatic proteolytic enzymes

Question 10

How are single amino acids transported across the cellular membrane?

Answer 10

cotransport with sodium

Question 11

How are the tri and di peptidases transported across the apical membrane?

Answer 11

PepT1 co-transporters

Question 12

What are the stages involved in the absorption of lipids?

Answer 12

1. Exposure to bile leads to the production of emulsified fat droplets
2. Combined action of lipase, co-lipase and bile leads to micells
3. Jejenum- diffusion of micelle components (with exception of the bile components into the cell)
4. Bile acid is re-aborbed in the ileum via specialised sodium co-transporter molecules

Question 13

What happens once the free fatty acids and monoglycerides are re-absorbed by the cell?

Answer 13

Once the free fatty acids and monoglycerides re-enter the cell they are resynthesised into triglycerides

Question 14

How does the leakyness of tissues change going from the duodenum to the distal colon?

Answer 14

The leakynness decreases

Question 15

How does sodium re-absorption occur within the small intestine?

Answer 15

via SGLT1 channels (sodium and glucose)

Question 16

How does sodium re-absorption occur within the small intestine and colon?

Answer 16

NHE3 (via hydrogen and sodium exchanger)

Question 17

How does sodium re-absorption occur within the ileum and the proximal colon?

Answer 17

Na+ reabosorption is coupled to movement of Cl- through a Cl-/HCO3- anion exchanger

Question 18

How does sodium-reabsorption occur within the distal colon?

Answer 18

distal colon Na+ reabsorption occurs through Na+ specific aldosterone sensitive ion channel

Question 19

How does potassium re-absorption occur within the small intestine?

Answer 19

passive re-absorption

Question 20

In the colon how does potassium secretion occur?

Answer 20

mainly via paracellular pathway driven by the osmotic gradient. However, this also occurs via apical channels as well

Question 21

How is potassium re-absorbed within the distal colon?

Answer 21

Active potassium re-absorption is occuring via an apical H+/K+ pump.

Question 22

How is chloride secreted in the small and large intestine?

Answer 22

Chloride is secreted in the small and large intestine from crypt cells