DIGESTION AND ABSORPTION OF CARBOHYDRATES AND PROTEINS

Question 1

What can be found in saliva?

Answer 1

Water
Ions
Salivary amylase
Lysozymes

Question 2

Where in the stomach would you find mucus cells?

Answer 2

Mostly in the cardiac and pyloric region

Question 3

What’s the function of mucus cells?

Answer 3

They secrete mucous to protect the epithelium from acid secretions

Question 4

Where would we mostly find parietal cells?

Answer 4

Mostly in the gastric region

Question 5

What’s the function of parietal cells?

Answer 5

To secrete hydrochloride acid and intrinsic factor

Question 6

Where would we mostly find chief cells in the stomach?

Answer 6

In the cardiac region

Question 7

What’s the function of chief cells?

Answer 7

Secreting pepsinogen, the precursor of pepsin

Question 8

Where in the stomach would we mostly find enteroendocrine cells?

Answer 8

In the gastric region

Question 9

What’s the function of enteroendocrine cells?

Answer 9

They secrete protein hormones e.g. somatostatin

Question 10

What volume of liquid can the stomach usually accommodate

Answer 10

2 litres

Question 11

What initiates the cephalon stage?

Answer 11

Seeing, smelling or tasting food

Question 12

What stimulates the salivary glands to secrete saliva?

Answer 12

The facial and glossopharyngeal nerves

Question 13

Describe how peristaltic action in the stomach is initiated?

Answer 13

Food distends the stomach and stimulates stretch receptors in its walls. When receptors are activated, nerve impulses activate parasympathetic and enteric neurones which cause a wave of peristalsis.

Question 14

Describe how the secretion of gastric juice occurs?

Answer 14

Chemoreceptors monitor the pH of the stomach chyme and when activates, nerve impulses activate the parasympathetic and enteric neurones which causes a secretion of gastric juice from gastric glands

Question 15

What is chyme?

Answer 15

When food in the stomach mixes with gastric juice

Question 16

Where is gastrin released from? What’s its function?

Answer 16

G cells of gastric glands
It stimulates gastric glands to secrete large amounts of gastric juice and strengthens the contraction of the lower oesophageal sphincter to prevent acid chyme reflux, it increases stomach motility and relaxes the pyloric sphincter = all of this increases gastric emptying

Question 17

At what ph is gastrin inhibited?

Answer 17

Below pH 2

Question 18

What is the intestinal phase of digestion?

Answer 18

When the chyme is found in the duodenum and the enterogastric reflex occurs

Question 19

What’s the enterogastric reflex?

Answer 19

Inhibition of gastric motility and increased contraction of the pyloric sphincter to increase gastric emptying

Question 20

What’s the function of cholecystokinin?

Answer 20

Stimulates secretion of pancreatic juice which causes contraction of the gall bladder to squeeze bile out and relax the sphincter of Oddi, slows gastric emptying by contracting pyloric sphincter and produces a feeling of fullness by acting on the hypothalamus, promotes normal growth/maintenance of the pancreas and enhances the effects of secretin

Question 21

Where is secretin released from and what are the effects?

Answer 21

It’s released from S cells of the intestinal glands in the small intestine which stimulates the flow of pancreatic juices to buffer the acidic chyme and it inhibits the secretion of gastric juice

Question 22

Where is histamine released from and how does it work?

Answer 22

Enterochromaffin like cells

They bind to H2 receptors on parietal cells and generate cAMP

Question 23

How does gastrin act?

Answer 23

It binds to CCK2 receptors and activates phospholipase C which induces the release of Ca2+ into the cytoplasm

Question 24

How does acetylcholine act on parietal cells?

Answer 24

It’s released from neurones and binds to M3 receptors which increases intracellular Ca2+ which helps the H+/K+ pump to work

Question 25

Why does the action of salivary amylase end in the stomach?

Answer 25

As the acidic pH destroys it

Question 26

What are the key enzymes in the mouth?

Answer 26

Salivary amylase and lingual lipase

Question 27

What are the key enzymes in the stomach?

Answer 27

Pepsin, gastric lipase

Question 28

What are the key enzymes in the small intestine?

Answer 28

Pancreatic amylase, lipase, phospholipase and professes e.g. trypsin, chymotrypsin, dipeptidases

Question 29

What are zymogens?

Answer 29

any of a group of proteins that display no catalytic activity but are transformed within an organism into enzymes e.g. pepsinogen gives rise to pepsin

Question 30

Which end-product from digestion and absorption enters the lymphatic system instead of the portal vein?

Answer 30

Chylomicrons

Question 31

Why do non-starch polysaccharides have particular nutritional value?

Answer 31

As they are the remains of plant cell walls and are resistant to digestion

Question 32

Why is resistant starch important?

Answer 32

It improves insulin sensitivity, lowers blood sugar levels, reduces appetite and helps digestion

Question 33

What is the glycaemic index?

Answer 33

The relative ability of carbon rate food to increase blood glucose levels

Question 34

Shorts chain fatty acids are produced by what?

Answer 34

The breakdown of non-digestible carbohydrates by gut bacteria

Question 35

What are some examples of short chain fatty acids?

Answer 35

Acetate
Propionate
Butyrate

Question 36

What are non-starch polysaccharides?

Answer 36

Polysaccharides found in food that aren’t starch e.g. inulin

Question 37

What’s the importantance of non-starch polysaccharides?

Answer 37

They absorb bile acids and cholesterol
Can absorb potential carcinogens in the colon
Increase the viscosity of gut contents to slow absorption
They can form short chain fatty acids in bacteria, fermentation which have benefits

Question 38

Where in the body is the control of energy intake?

Answer 38

The mouth