Physiology

Question 1

What are the divisions of the stomach?

Answer 1

Cardia = no parietal cells

Corpus (and fundus)

Pyloric Antrum

Question 2

What in the stomach increase surface area?

Answer 2

Gastric glands

• Mucous cells
• parietal cells
• chief cells
• endocrine cells

Question 3

How much and what fluid do gastric glands make in a day?

Answer 3

2 Litres/day

• parietal secretion = H+ rich (stimulated)
• non-parietal secretion = Na+ rich (basal)

Question 4

Which cells produce bicarbonate and mucous?

Answer 4

Foveolar cells = surface epithelial cells

Question 5

Which cells does the corpus of stomach include?

Answer 5

Parietal

Chief (peptic) cells

Mucous cells

Endocrine cells

Question 6

What do parietal cells release?

Answer 6

Acid

Intrinsic factor

Question 7

What is the importance of intrinsic factor?

Answer 7

Necessary for the absorption of vitamin B12 (essential for brain + nervous functioning and blood formation) later in the small intestine

Question 8

What do chief cells release?

Answer 8

Pepsinogens

Question 9

What is the importance of pepsinogens?

Answer 9

Activated to pepsins at pH < 3

Pepsins initiate protein digestion by hydrolysing peptide bonds

Note: pepsinogen secretion parallels acid secretion

Question 10

Where are mucous cells located?

Answer 10

In the neck of gland

Question 11

What are the endocrine cells and what do they secrete?

Answer 11

Enterochromaffin-like cells

Secrete histamine

Question 12

What cells are located in the pyloric antrum?

Answer 12

Chief cells
Endocrine cells
G cells
D cells

Note: No parietal cells

Question 13

What do G cells secrete?

Answer 13

Gastrin

Question 14

What is the importance of gastrin?

Answer 14

Stimulates the secretion of acid

Question 15

What do D cells secrete?

Answer 15

Somatostatin

Question 16

What is the importance of somatostatin?

Answer 16

Suppreses the release of other GI hormones

Delay gastric emptying by reducing smooth muscle contractions

Question 17

What are the phases of gastric secretion?

Answer 17

Basal (post-prandially vs. interdigestive phase)

Cephalic (sight, smell, taste)

Gastric (stomach distension due to food)

Intestinal (protein digestion products)

Question 18

Which nerve is stimulated in cephalic stage of gastric secretion and what is the effect?

Answer 18

Vagus nerve

Increased ACh release, causing:

• acid secretion
• histamine release
• gastrin

Decreased stimulation of D cells
- less somatostatin

Question 19

Which reflex occur with the gastric phase and what is the effect?

Answer 19

Local enteric nervous system (ENS) reflexes
- ACh released

Vasovagal reflex
- ACh released

Ach causes:

• acid secretion
• histamine release
• gastrin

Question 20

Describe the gastroduodenal mucosal defence.

Answer 20

Mucous HCO3- layer
- physiochemical barrier releasing HCO3-

Surface epithelial cells = mucous production

Question 21

What are the role of prostaglandins?

Answer 21

Central role in gastric epithelial defence and repair

Question 22

How do prostaglandins repair and defend gastric epithelium?

Answer 22

Regulate release of bicarbonate and mucus

Maintain mucosal blood flow

Cell restitution (maintain/repair)

Question 23

Describe the process of prostaglandins synthesis

Answer 23

Phospholipids —- (phospholipase A2) —> arachidonic acid —- (COX) —–> prostaglandins

Question 24

What are the reasons for NSAIDs causing peptic ulcers?

Answer 24

Affect COX as a result stop action of prostaglandins

Question 25

Why are NSAIDs better than COX-2 inhibitors?

Answer 25

Cardiac issues associated with COX-2 inhibitors

Question 26

Where are COX expressed/induced?

Answer 26

COX 1
- expressed in stomach, platelets, kidneys, endothelium

COX 2
- inducible by inflammatory stimuli