Lecture 11

Question 1

What is pyloric sphincter?

Answer 1

Doorway to small intestine

Question 2

Function of pyloric sphincter?

Answer 2

Regulates movement of contents

Question 3

3 main parts of stomach (top to bottom)?

Answer 3

Fundus, body, antrum

Question 4

What does body of stomach secrete?

Answer 4

Mucous, pepsinogen, HCl

Question 5

What does antrum secrete?

Answer 5

Mucous, pepsinogen, gastrin

Question 6

What is chyme?

Answer 6

Partially digested food

Question 7

What is secretion of intrinsic factor essential for?

Answer 7

Absorption of vitamin B12

Question 8

What does the muscularis mucosa enable during mechanical digestion?

Answer 8

Food to be churned to ensure optimal coverage from secretions

Question 9

What part of stomach has thicker muscle wall?

Answer 9

Antrum (stronger contractions)

Question 10

Function of peptic (chief) cell?

Answer 10

Secrete pepsinogen (inactive form of pepsin)

Question 11

Function of parietal (oxyntic) cells?

Answer 11

Secrete HCl (and intrinsic factor)

Question 12

Function of goblet (neck) cells?

Answer 12

Secrete mucous (for good lubrication to mix contents)

Question 13

Function of G cells?

Answer 13

Secrete gastrin

Question 14

Function of enterochromaffin (mast like) cells?

Answer 14

Secrete histamine

Question 15

Function of D cells?

Answer 15

Secrete somatostatin

Question 16

Where are most parietal cells located in stomach?

Answer 16

Body (not antrum - most of pepsin has acted on contents by this stage)

Question 17

Function of pepsin?

Answer 17

Breaks down proteins, only in acidic environment (converted from pepsinogen by HCl)

Question 18

Function of gastric lipase?

Answer 18

Breaks down fat at higher pH (5-6)

Question 19

Formation of acid in parietal cell?

Answer 19

CO2 from bloodstream produces carbonic acid which is broken down to protons and bicarbonate ions. Protons are transported out into lumen by pump, subsequent transport of Cl- ions

Question 20

What prevents leakage of gastric juice onto underlying tissue?

Answer 20

Tight junctions between mucosal epithelial cells and lumen of stomach

Question 21

What does mucous secreted by epithelial/goblet cells with higher pH do?

Answer 21

Provides localised neutralisation and physical barrier to acid

Question 22

What do prostaglandins do?

Answer 22

Increase mucosal thickness and stimulate bicarbonate production (inhibits proton pump activity)

Question 23

Gastric secretion phases?

Answer 23

Cephalic phase (increased)
Gastric phase (increased)
Intestinal phase (decreased)

Question 24

What is cephalic phase stimulated by?

Answer 24

Sight, smell, taste, though of food/decrease in blood glucose

Question 25

What occurs during cephalic phase?

Answer 25

Nerve impulses to medulla cause parasympathetic neurones via vagus nerves to increase HCl and pepsin
Gastrin secretion promoted in antrum which stimulates further HCl and pepsin secretion

Question 26

What is gastric phase stimulated by?

Answer 26

Stomach digestion due to presence of food

Question 27

What occurs during gastric phase?

Answer 27

Stomach digestion triggers parasympathetic reflex leading to further HCl, pepsin and gastrin secretions

Question 28

What is intestinal phase stimulated by?

Answer 28

Digested proteins/fats/low pH in duodenum

Question 29

What occurs during intestinal phase?

Answer 29

Secretion decreased by:
Neuronal impulses sent to medulla which decrease parasympathetic stimulation of gastric glands (enterogastric reflex)
Local reflexes in gut wall
Release of hormones secretin, gastric inhibitory peptide and cholecystokinin via bloodstream to gastric glands

Question 30

Role of somatostatin (paracrine agent)?

Answer 30

Involved in HCl inhibition - released in response to increased HCl concentration