L04 - Secretions of stomach

Question 1

What are the different functions of the stomach

Answer 1

1. Stores food
2. Mixes food with secretions
3. Regulates release of food into duodenum
4. Secretes gastric juices

Question 2

What is the greater curvature a point of attachment for?

Answer 2

Point of attachment for the gastrosplenic ligament and the greater omentum

Question 3

What is the lesser curvature a point of attachment for?

Answer 3

Point of attachment for the lesser omentum

Question 4

What is the cardiac notch?

Answer 4

The superior angle created when the oesophagus enters the stomach

Question 5

What is the angular incisure?

Answer 5

A bend on the lessuer curvature

Question 6

What are the different types of cells found in the gastric gland?

Answer 6

1. Mucous neck cells
2. Parietal cells
3. EC (enterochromaffin) like cells
4. Chief cells
5. D cells
6. G cells

Question 7

What is secreted from mucous neck cells?

Answer 7

1. Bicarbonate

2. Mucous with mucin

Question 8

What is secreted from parietal cells?

Answer 8

• Hydrochloric acid
• Gastric intrinsic factor (IF)
  Both released into the lumen of the stomach

Question 9

What is secreted from EC like cells?

Answer 9

Histamine

Question 10

What is secreted from chief cells?

Answer 10

• Pepsinogen
• Gastric lipase
• Renin
  Released into lumen of stomach

Question 11

What is secreted from D cells?

Answer 11

Somatostatin (inhibitor)

Question 12

What is secreted from G cells?

Answer 12

Gastrin

Question 13

What will an absence of gastric IF cause a deficiency in?

Answer 13

Deficiency in vit B12 as GIF is a glycoprotein necessary for VB12 abs from the ileum
- Consequent dev of pernicious anaemia

Question 14

What cells would you find in the corpus of the stomach?

Answer 14

Predom parietal and chief cells

does also contain ECL and D cells

Question 15

What is the mechanism of gastric acid secretion (parietal cell stimulation)? (draw)

Answer 15

1. CO2 and H2O combine within the parietal cell to form H2CO3 (carbonic acid)
2. Carbonic anhydrase breaks down carbonic acid into protons and bicarbonate ions
3. Bicarbonate ions are then transported out of the cell into the blood via an anion exchanger
   - Transports bicarbonate ion out of the cell in exchange for chloride ion
4. Chloride ion is then transported into stomach lumen via chloride channel
5. Protons transported into the stomach lumen via the proton-potassium pump (this channel uses ATP to exchange potassium ions with protons
6. The opposite charges of chloride ion and proton causes them to associate to form HCl

Question 16

What directly regulates acid secretion?

Answer 16

• ACh (neural)
• Histamine (paracrine)
• Gastrin (endocrine)

Question 17

What indirectly regulates acid secretion?

Answer 17

• ACh

- Gastrin mediated histamine release by ECL cells

Question 18

What are the 4 phases of gastric acid secretion?

Answer 18

1. Basal
2. Cephalic
3. Gastric
4. Intestinal

Question 19

What can helicobacter pylori cause?

Answer 19

• Gastritis
• Gastric and duodenal ulcers
• Gastric cancer (WHO) class 1 carcinogen

Question 20

What causes acid prod to decrease?

Answer 20

1. Accumulation of acid in empty stomach between meals

2.

Question 21

How does gastrin stimulate acid secretion?

Answer 21

• Gastrin binds to the cholecystokinin B receptor (CCKB)

- Activates PKC (protein kinase C)

Question 22

How does ACh stimulate acid secretion?

Answer 22

• Binds to an M3 muscarinic receptor

- This culminates in activation of protein kinase Ca2+ channel (PKC) and intracellular calcium

Question 23

How does histamine stimulate acid secretion?

Answer 23

• Activation of the H2 receptors stimulates adenyl cyclase

- Resulting in prod of cAMP and activation of PKA