Gastric Secretion

Question 1

What are the three main functional parts of the stomach?

Answer 1

Fundus, body and antrum

Question 2

What is the fundus of the stomach responsible for?

Answer 2

Storage

Question 3

What are the functions of the body of the stomach?

Answer 3

Storage 
Mucous production 
HCl production 
Pepsinogen production 
Production of intrinsic factor

Question 4

What are the functions of the antrum of the stomach?

Answer 4

Mixing and grinding of the stomach contents

Production of gastrin

Question 5

What feature of the antrum aids the mixing and grinding of the stomach contents?

Answer 5

Very thick muscularis externae

Question 6

Where is gastrin released and what does it do?

Answer 6

Released in the antrum, gastro-intestinal hormone which is secreted into stomach lumen, taken into circulation then returned to stimulate the stomach cells

Question 7

What three mechanisms control gastric acid secretion?

Answer 7

Neurocrine - vagus nerve and local reflexes
Endocrine - gastrin
Paracrine - histamine

Question 8

What is the first thing to prepare the stomach for digestion and what does this cause?

Answer 8

Precursors to eating - sight, smell and taste of food

Causes stomach to create acid which will instantly sterilise any bacteria ingested

Question 9

What three things are stimulated by the vagus nerve or by gastrin in the cephalic phase to trigger acid production?

Answer 9

Stomach
G cells
ECL cells

Question 10

When does the gastric phase occur?

Answer 10

Once there is a physical presence of food in the stomach

Question 11

Distension of the stomach (gastric phase) triggers long reflexes from the _ and short reflexes from the _

Answer 11

Vagus nerve

Enteric reflexes

Question 12

Vagus nerve and enteric reflexes trigger the release of

Answer 12

ACh

Question 13

Peptides in the lumen stimulate

Answer 13

G cells which release gastrin

Question 14

Gastrin and ACh can also stimulate the ECL cells which release

Answer 14

histamine

Question 15

What will inhibit gastric acid secretion in the cephalic phase?

Answer 15

Absence of stimulus i.e. stop eating

Question 16

What will inhibit gastric acid secretion in the gastric phase?

Answer 16

H ion increases, pH decreases leading to decreased gastrin release as environment is acidic enough

Question 17

Pancreatic enzymes are extremely sensitive to

Answer 17

acid/low pH

Question 18

Acid in the duodenum triggers

Answer 18

the enterogastric reflex and secretin release from the surface of the duodenum

Question 19

Secretin triggers the release of

Answer 19

bicarbonate

Question 20

Secretin and bicarbonate will cause

Answer 20

reduction in gastric secretion and therefore reduce the effect of gastrin stimulation on the parietal cells

Question 21

Fat in the duodenum causes the release of _ which causes

Answer 21

gastric inhibitory peptide

causes reduced gastric secretion and reduced parietal HCl secretion

Question 22

The intestinal phase occurs when

Answer 22

signals are sent that the stomach is emptying its contents

Question 23

The intestinal phase reduces

Answer 23

acid damage to the duodenum

Question 24

What is pepsinogen?

Answer 24

The zymogen of pepsin

Question 25

What is a zymogen?

Answer 25

An inactive precursor of an enzyme

Question 26

When is pepsinogen converted to pepsin?

Answer 26

When the pH is below 3

Question 27

When are pepsins inactivated?

Answer 27

At neutral pH

Question 28

Gastric motility causes the

Answer 28

mixing of the stomach contents, contraction of pyloric sphincter and further mixing

Question 29

What is the function of the pyloric sphincter?

Answer 29

Controls passage of stomach contents into the duodenum

Question 30

What are responsible for gastric motility?

Answer 30

Peristaltic waves

Question 31

Where do peristaltic waves originate?

Answer 31

Oesophagus

Question 32

Why are more powerful contractions possible once the peristaltic wave reaches the antrum and pyloric sphincter?

Answer 32

As the muscle here is thicker and more powerful

Question 33

Does gastrin increase or decrease contraction in the stomach?

Answer 33

Increase

Question 34

How is the stomach emptied?

Answer 34

Gradually

Question 35

The presence of what in the duodenum will inhibit gastric motility?

Answer 35

Fat Acid Amino acids Hypertonicity

Question 36

What is the only essential, non-compensated function of the stomach?

Answer 36

Releasing intrinsic factor to form a complex with vitamin B12, allowing it to be absorbed from the ileum

Question 37

What will a defect in intrinsic factor lead to?

Answer 37

Pernicious anaemia

Question 38

What cells produce gastric mucous?

Answer 38

Surface epithelial cells and mucous neck cells

Question 39

What role does gastric mucous have?

Answer 39

Cytoprotective role

Question 40

What is the function of the high bicarbonate content of gastric mucous?

Answer 40

Neutralises the pH of gastric acid, completely denaturing pepsin and stopping the corrosive acid from reaching the cells below the mucous layer