Gastric secretion

Question 1

What is the fundus of the stomach mainly used for?

Answer 1

storage

Question 2

List some of the stomach bodies uses

Answer 2

storage

Produce mucus, HCL, pepsinogen and intrinsic factor

Question 3

Why is mucus important in the stomach?

Answer 3

To protect from acid

Question 4

What is pepsinogen a precursor for and why is it stored in this way?

Answer 4

pepsin - to prevent autodigestion

Question 5

Where is gastrin synthesised?

Answer 5

the ANTRUM and duodenum

Question 6

What is gastrin?

Answer 6

A hormone produced from g cells which initiates gastric acid secretion by acting on cells in the stomach

Question 7

What is the gastric pit?

Answer 7

The top part of the gastric gland containing the surface mucousal cells

Question 8

What do the mucousal neck cells produce? What is special about these cells?

Answer 8

mucus

can migrate upwards to become surface mucousal cells

Question 9

What are the 3 parts of the gastric gland?

Answer 9

mucous neck cells, parietal cells and chief cells

Question 10

What do the parietal cells produce?

Answer 10

HCL, intrinsic factor

Question 11

What do the chief cells produce?

Answer 11

pepsinogens

Question 12

Why is it very important for the tight junctions between the cells in gastric glands to be very tight?

Answer 12

to prevent acid getting in

Question 13

What 3 substances turn on gastric acid secretion?

Answer 13

Gastrin, histamine and acetylcholine

Question 14

What substance turns off gastric acid secretion?

Answer 14

prostaglandins

Question 15

What cells does gastrin work on?

Answer 15

parietal cells

Question 16

What is released to work on the protein kinase in terms of gastrin?

Answer 16

calcium

Question 17

Explain the similarities and differences between prostaglandin and histamine action on gastric acid secretion

Answer 17

Histamine is stimulatory of adenylate cyclase to convert ATP to cAMP whereas prostaglandins inhibits this process to turn on the cyclic kinase

Question 18

How is acetylcholine production innervated?

Answer 18

By parasympathetic nerves to act on muscarinic cholinergic receptors

Question 19

What messenger is used in terms of acetylcholine and gastric acid secretion?

Answer 19

calcium

Question 20

What are the 3 broad mechanisms of gastric acid secretion?

Answer 20

neurocrine
endocrine
paracrine

Question 21

When does the cephalic phase of digestion begin? What does this innervate?

Answer 21

thought, smell, sight of food and whilst eating

vagus nerve

Question 22

What does the vagus nerve stimulate in the cephalic phase?

Answer 22

acetylcholine release
Work on g cells to form gastrin
These both work on parietal cells

Question 23

What other chemical do acetylcholine and gastrin act on in the cephalic phase?

Answer 23

ECL cells to release histamine which also works on the parietal cells

Question 24

What is the gastric phase?

Answer 24

food has physically entered the stomach

Question 25

What does the distension of the stomach do in the gastric phase?

Answer 25

vagal (long) and enteric (short) reflexes releasing acetylcholine to act on parietal cells

Question 26

What stimulates the G cells to release gastrin in the gastric phase?

Answer 26

peptides in the lumen

Question 27

What stimulates histamine release in the gastric phase?

Answer 27

Same as in the cephalic phase - gastrin and acetylcholine work on ECL cells to promote histamine release

Question 28

What inhibits the cephalic phase of producing acid?

Answer 28

stopping eating as this reduces vagal activity

Question 29

Why does the gastric phase cease to produce acid?

Answer 29

pH falls as the acid is produced and this works by negative feedback and reduces gastrin secretion

Question 30

What 2 things does acid in the duodenum stimulate?

Answer 30

enterogastric reflex | secretin release

Question 31

What does acid sensed in the duodenum ultimately lead to?

Answer 31

reduced gastrin secretion and decreased gastrin stimulation of parietal cells

Question 32

What happens when fat is sensed in the duodenum?

Answer 32

GIP is released to decrease gastrin secretion and parietal HCL secretion

Question 33

What are enterogastrones?

Answer 33

Hormones released from gland cells in the duodenal mucosa

Question 34

What are the 3 enterogastrones?

Answer 34

secretin, CCK, GIP

Question 35

What 4 situations are enterogastrones released in response to?

Answer 35

acid ALL IN DUODENUM hypertonic solutions fatty acids monoglycerides

Question 36

What do enterogastrones allow?

Answer 36

Prevention of acid buildup in the duodenum

Question 37

What 2 ways do enterogastrones prevent acid buil up?

Answer 37

reduce gastric motility and gastric acid secretion

Question 38

What is a zymogen?

Answer 38

An inactive precursor

Question 39

Why is pepsin stored as an inactive precursor?

Answer 39

to prevent autodigestion

Question 40

What cells secrete pepsinogen?

Answer 40

chief cells

Question 41

Is the pepsinogen-pepsin loop positive or negative feedback?

Answer 41

positive

Question 42

What pH is pepsin inactivated?

Answer 42

neutral

Question 43

What cells in the gastric gland secrete mucus?

Answer 43

Epithelial surface cells and mucous neck cells

Question 44

In what 2 ways does mucus protect?

Answer 44

From injury - lubrication | From acid - bicarbonate present

Question 45

What is the only essential function of the stomach?

Answer 45

intrinsic factor

Question 46

What cells produce intrinsic factor?

Answer 46

parietal cells

Question 47

Why is intrinsic factor needed?

Answer 47

Vitamin B12 absorption - prevent pernicious anaemia

Question 48

Where is the vit B12 - intrinsic factor absorbed?

Answer 48

ileum