Gastric secretion

Question 1

What is the fundus?

Answer 1

Upper part forming the majority of the stomach

Question 2

What is the structure of the fundus?

Answer 2

Thinner musculature

Pleats on surface allow for increase in volume

Question 3

What is the function of the fundus?

Answer 3

Storage

Question 4

What is the function of the body of the stomach?

Answer 4

Storage
Mucus
HCl production for sterilisation
Pepsinogen production
Intrinsic factor production

Question 5

What is the function of the antrum?

Answer 5

Mixing and grinding

Gastrin production

Question 6

What is the cellular composition of gastric glands?

Answer 6

Mucous neck cells
Chief cells
Parietal cells

Question 7

What is the function of mucous neck cells?

Answer 7

Secrete mucus

Question 8

What are mucous neck cells?

Answer 8

Immature surface cells

Question 9

What is the function of chief cells?

Answer 9

Secrete pepsinogen

Question 10

What is the function of parietal cells?

Answer 10

Secrete HCl and intrinsic factor

Question 11

How does water pass from the stomach lumen to the bloodstream?

Answer 11

Passes through tight junctions between the parietal cells

Question 12

What happens to CO2 in the stomach lumen?

Answer 12

Passiveley enters the parietal epithelium and binds with H20 to form H2CO3

Question 13

What happens to H2CO3 in the parietal epithelium?

Answer 13

Splits into HCO3 and H
H is transported into lumen as K is transported in
HCO3 transported into blood as Cl is transported in

Question 14

What happens to H in the stomach lumen?

Answer 14

Binds with Cl to form HCl and lower the stomach pH

Question 15

What secretions have an effect on the stomach?

Answer 15

Gastrin
Histamine
Acetylcholine
Prostaglandins

Question 16

What does gastrin do?

Answer 16

Activates a receptor on the basolateral membrane causing a rise in intracellular Ca, that tells protein kinases to pump more H across the apical membrane, decreasing the pH of the stomach lumen

Question 17

What does histamine do?

Answer 17

Stimulated the H2 receptor inducing uptake of CO2 and H2O which in turn decrease the pH of the stomach lumen

Question 18

What does acetylcholine do?

Answer 18

Cause increase in intracellular Ca, that tells protein kinases to pump more H across the apical membrane, decreasing the pH of the stomach lumen

Question 19

What do prostaglandins do?

Answer 19

Couple themselves to inhibited G proteins and reduce protein kinase activity to even out the pH of the stomach lumen

Question 20

What is the main release of acetylcholine and what does it act on for the stomach?

Answer 20

Vagus nerve

Muscarinic cholinergic

Question 21

What are the 3 types of control of gastric secretion?

Answer 21

Neurocrine
Endocrine
Paracrine

Question 22

What is the neurocrine control of gastric secretion?

Answer 22

Acetylcholine from Parasympathetic- Vagus and ENS

Question 23

What is endocrine control of gastric secretion?

Answer 23

Gastrin

Question 24

What is paracrine control of gastric secretion?

Answer 24

Histamine

Local effect

Question 25

What are the 2 mechanisms stimulating gastric secretions?

Answer 25

Cephalic phase | Gastric phase

Question 26

Why is the cephalic phase of secretion important?

Answer 26

Create acidity before food arrives in the stomach so it can be sterilised immediately

Question 27

What happens in the cephalic phase of secretion?

Answer 27

Sight, smell and taste of food causes an increase in vagus activity causing Ach release and gastrin release

Question 28

What happens during the gastric phase of secretion?

Answer 28

Distension of stomach activates vagal and enteric reflexes, releasing Ach Peptides in limen activate G cells to release gastrin Gastrin and Ach act on ECL to release histamine

Question 29

What happens in the cephalic phase on inhibition?

Answer 29

Stop eating causes a decrease in vagal activity

Question 30

What happens in the gastric phase of inhibition?

Answer 30

Decrease of lumen pH causes a decrease in gastrin secretion so pH doesn't drop too low

Question 31

What kind of reaction is the gastric phase of inhibition?

Answer 31

Negative feedback

Question 32

What initiates the intestinal phase of inhibition?

Answer 32

Acid or fat in duodenum

Question 33

What does acid in the duodenum cause?

Answer 33

Enterogastric reflex and secretin release, decreasing gastrin secretion and stimulation

Question 34

What does acid in the duodenum indicate?

Answer 34

Stomach is empty

Question 35

What does fat in the duodenum cause?

Answer 35

GIP release, decreasing gastrin and parietal HCl secretion

Question 36

What are enterogastrones?

Answer 36

Hormones released from gland cells in duodenal mucosa

Question 37

What are the main enterogastrones?

Answer 37

Secretin CCK GIP

Question 38

What are enterogastrones released in response to?

Answer 38

``` Acid Hypertonic solutions Fatty acids Monoglycerides in the duodenum ```

Question 39

What do enterogastrones aim to do?

Answer 39

Prevent any acid getting into the duodenum

Question 40

What are the 2 methods of action of enterogastrones?

Answer 40

Inhibit gastric secretion | Reduce gastric emptying- inhibit motility and contract pyloric sphincter

Question 41

What is pepsinogen?

Answer 41

Inactive precursor to pepsin

Question 42

What activated pepsinogen to turn into pepsin?

Answer 42

pH of below 3

Question 43

Why is pepsin stored in its inactive form?

Answer 43

To prevent cellular damage

Question 44

How is pepsin deactivated?

Answer 44

When the stomach reaches a neutral pH or pepsin enters and area of neutral pH

Question 45

What are the mechanisms for control of pepsin?

Answer 45

Sight, smell and taste of food causes an increase in vagus activity causing Ach release and gastrin release- lowering pH and activating pepsin Distension of stomach activates vagal and enteric reflexes, releasing Ach Peptides in limen activate G cells to release gastrin Gastrin and Ach act on ECL to release histamine- lowering pH and activating pepsin

Question 46

Where is gastric mucus produced?

Answer 46

Epitelial cells and mucus neck cells

Question 47

What is the role of gastric mucus?

Answer 47

Cytoprotective Protects mucosal surface from mechanical injury Protects against gastric acid corrosion and pepsin digestion

Question 48

How does the mucus protect against gastric acid and pepsin?

Answer 48

Gastric acid neutralised by bicarbonate buffer | Pepsin deactivated by neutral pH