Digestion, Absorption and Intestinal Secretion

Question 1

What is the role of the parotid glands?

Answer 1

secrete serous saliva which is watery and rich in amylase

Question 2

What is the role of the sublingual and submandibular glands?

Answer 2

produce a mixture of serous and mucus secretion which serves as an antimicrobial and a lubricant

Question 3

How does amylase work?

Answer 3

breaks onw the alpha-1,4 glycolytic bonds in glycogen etc.

Question 4

What do stomach secretions contain?

Answer 4

hydrochloric acid, pepsin, mucus, salts, water, intrinsic factor (critical for vit b12 absorption) and bicarbonate

Question 5

How is gastric acid secretion stimulated?

Answer 5

driven by gastrin which is released by G cells in the antral part of the stomach in response to the presence of peptides. The release of gastrin stimulates CCKB receptors on parietal cells to produce acid as well as on ECL cells in the corpus to secrete histamine, which then stimulates parietal cells via the H2 receptor

Question 6

How is gastric acid secretion inhibited?

Answer 6

somatostatin released by D cells which inhibits the G cells, ECL cells and parietal cells via SST2 receptors as well as reducing excitatory control via the vagus nerve to the cells.

Question 7

Describe the role of pepsin in the stomach

Answer 7

secreted as pepsinogen by chief cells

Question 8

Describe the composition of pancreatic secretions

Answer 8

rich in bicarbonate and contains trypsin inhibitor (to prevent premature activation in the pancreatic ducts)

Question 9

What is the function of bile salts?

Answer 9

Bile salts are synthesised from cholesterol and promote the emulsification of fats into droplets

Question 10

What is bile?

Answer 10

composition of bile acids formed from cholesterol

Question 11

What happens to the bile after it has been produced?

Answer 11

secreted into the canaliculi of hepatocytes and travels in the liver ducts to the gall bladder where it is stored until stimulated for release

Question 12

How is the release of bile stimulated?

Answer 12

by the presence of acetylcholine, gastrin or CCK

Question 13

What is the sphincter of oddi and what is it’s function?

Answer 13

allows the flow of bile into the duodenum when opened, and when closed prevents this (when not stimulated)

Question 14

What are bruner cells and where would you find them?

Answer 14

secrete bicarbonate rich mucus in the small intestine

Question 15

What are peyer’s patches and where are they found?

Answer 15

an aggregate of lymphoid tissue in the large intestine

Question 16

Where does fat breakdown occur?

Answer 16

small intestine

Question 17

What does the hydrolysis of emulsified fats produce?

Answer 17

micelles (nanometre particles of lipid digestion)

Question 18

What are micelles and how are they formed?

Answer 18

consist of 2 monoglycerides

Question 19

What are the products of cholesterol breakdown by cholesterol esterase?

Answer 19

fatty acid and free cholesterol

Question 20

Where is carbohydrate digestion facilitated in the small intestine?

Answer 20

conducted by brush border enzymes on the enterocytes

Question 21

Where is peptide digestion facilitated in the small intestine?

Answer 21

conducted by brush border enzymes on the enterocytes

Question 22

Describe lymphatic routes of nutrient transport

Answer 22

Only really used for lipid molecules too large to pass through into the capillary

Question 23

Describe portal routes of nutrient transport

Answer 23

Carries molecules from the small intestine to the liver

Question 24

Describe the different types of amino acid transporters

Answer 24

There are at least 5 types: three are sodium-independent transporters which are involved in the efflux of amino acids, whereas there are two sodium-dependent channels which are used for the uptake of amino acids

Question 25

Describe what happens when amino acids are transported into an enterocyte

Answer 25

90% are transported across the basolateral membrane, 10% remain in the cell where they serve role in intracellular protein synthesis

Question 26

Describe how micelles are absorbed in the small intestine

Answer 26

diffuse through to reach the brush border

Question 27

Describe how fatty acids, cholesterol and phospholipids are absorbed in the small intestine

Answer 27

absorbed by free diffusion

Question 28

Why may fat be taken up into the lymph circulation?

Answer 28

if they are too large to pass into the capillary