Transport across alimentary tract

Question 1

What are the intrinsic neuronal plexuses of the gut?

Answer 1

submucoal plexus (meissner plexus)
Myenteric plexus (Auerbach plexus)

Question 2

What are the extrinsic control of GI tract?

Answer 2

• long reflexes arising within or outside GI tract
• involve CNS centres and extrinsic autonomic nerves
• parasympathetic reflexes

Question 3

Describe the structure of small intestine?

Answer 3

epithelial folds, villi and microvilli (large SA)
thin and highly vascularised
can replace itself -> has stem cells particularly within crypt cells that can allow rejuvenation + replacement of dead cells

Question 4

What are 2 type of transport across enterocyte?

Answer 4

transcellular (across cell) e.g. gluocse transport

paracellular(between gap junctions, between 2 cells) e.g. Na+, Cl- and H2O

Question 5

What is enterocyte?

Answer 5

cell of intestinal lining

Question 6

Describe how carbohydrate is digested and absorbed?

Answer 6

can only be absorbed in form of monosaccharides
complex carbohydrate reduced disaccharide by amylases
specific brush border convert disaccharides to monosaccharides

Question 7

In what process is glucose and galactose rapidly absorbed?

Answer 7

Secondary active transport process

Question 8

What is basolateral side?

Answer 8

Blood side of gut

Question 9

What is SGLUT1?

Answer 9

Is cotransporter

Good at transporting galactose so if galactose gets there first before glucose it will inhibit it

Question 10

What does GLUT2 transport?

Answer 10

Transports glucose, fructose and galactose

Question 11

What does SGLUT1 co transport?

Answer 11

Na+ along with glucose and galactose

Question 12

What is apical side?

Answer 12

Top side of the gut

Question 13

What is basolateral side?

Answer 13

Bottom side

Blood side of gut

Question 14

Polypeptides are produced by action of..

Answer 14

Pepsin

Question 15

What do dipeptidases in the brush border do?

Answer 15

They complete digestion to amino acids

Question 16

Are dipeptides and tripeptides able to cross/ pass through gap junctions?

Answer 16

No because they are complex structures so we generally digest tripeptides and dipeptides into amino acids which are then transported

Question 17

How are amino acids transported?

Answer 17

Transported on a sodium coupled carrier system similar to that of glucose

Question 18

Digestion and absorption of lipids are facilitated by 2 important processes. What are they?

Answer 18

Emulsification

Micelle formation

Question 19

What is emulsification of fats?

Answer 19

Bile salts emulsify fats-> break large fat globules into smaller globules

Question 20

What is benefit of emulsification?

Answer 20

Surface area where lipase can act is increased

Question 21

What is function of colipase?

Answer 21

It helps lipase action
It binds to this emulsion droplet and will allow lipase to attach to other end of lipid core. It then flips and is able to bury into lipid core and allows digestion to occur more efficiently

Question 22

What are 3 phase of fat digestion?

Answer 22

Oil phase
Viscous isotropic phase
Micellar phase

Question 23

How are lipids transported?

Answer 23

Digestive components of lipids don’t end up directly into blood -> go via lymphatic system

Question 24

How are bile salts recycled by the body?

Answer 24

Some will be excreted in faeces but only small percentage will be recirculated via process called enterohepatic recirculation

Question 25

What are some disorders of fat digestion/absorption?

Answer 25

Gallstones, pancreatitis, Crohn’s disease and liver disease can lead to fat malabsorption ( steatorrhoea or fat diarrhoea=excess fat in faeces)