L3 Secretions of the Stomach

Question 1

Functions of the Stomach?

Answer 1

• Secretions: different cell types
• Motility: peristalsis
• Digestion: Carbohydrates, protein and fat
• Absorption e.g. alcohol and drugs like aspirin

Question 2

What are the 3 main parts of the stomach?

Answer 2

Cardia
Oxyntic mucosa
Pyloric

Question 3

What is the cardia?

Answer 3

Beginning part of the stomach near gastroesophageal sphincter

Question 4

What is the oxyntic mucosa?

Answer 4

Fundus and body (corpus)

Question 5

What is pyloric?

Answer 5

Antrum and pyloric sphincter

Question 6

Why are there infoldings within the stomach/

Answer 6

To increase the surface area to enhance the action of digestion

Question 7

What are the pits within the stomach known as?

Answer 7

Gastric pits

Question 8

What structures sits at the top of gastric pits?

Answer 8

Gastric glands

Question 9

Substance secreted from mucous neck cells?

Answer 9

• Mucous
• Bicarbonate (HCO3-)

Question 10

Substance secreted from parietal cells?

Answer 10

Acid and Intrinsic factor

Question 11

Substance secreted from EC like cell (Enterochromaffin-like)?

Answer 11

Histmaine

Question 12

Substance secreted from chief cells?

Answer 12

Pepsinogen & lipase

Question 13

Substance secreted from D cells?

Answer 13

Somatostatin

Question 14

Substance secreted from G cells?

Answer 14

Gastrin

Question 15

What is the difference between antrum and corpus gastric pits?

Answer 15

• Antrum gastric pits (towards end of stomach) are deeper than the corpus gastric pits (body of stomach)
• Antrum produced more mucus than corpus

Question 16

What cells secrete stomach acid?

Answer 16

Parietal cells

Question 17

Describe the process of acid secretion by the parietal cells

Answer 17

• Cl- transported from the cytoplasm of the parietal cells into the lumen with Na+ pumped in at the same time
• Na+ transported from the canaliculus into the cytoplasm of the parietal cell
• Water dissociates into H+ and OH- in the cytoplasm of the cell
• The H+ are secreted into the canaliculus in exchange for K+ - proton pump used
• CO2 combines with OH- to form bicarbonate ions (HCO3-) using carbonic anhydrase.
• HCO3- diffuse out of the cell cytoplasm into the extracellular fluid in exchange for Cl- (alkaline tide)
• A canaliculus is an adaptation found on gastric parietal cells. It is a deep infolding, or little channel, which serves to increase the surface area, e.g. for secretion
• Na+ leaves the parietal cell back into the interstitial space using Na+/K+ pump

Question 18

What nerve controls direct regulation of acid secretion?

Answer 18

Vagus nerve

Question 19

What receptor acts to increase acid secretion directly?

Answer 19

Acetylcholine (ACh)

Question 20

Describe the 2 ways in which indirect regulation of acid secretion occurs?

Answer 20

1) Act on G cells by releasing gastrin releasing peptide - secrete gastrin - act on CCKB receptor of parietal cells - increases HCl secretion
2) Act of ECL - secrete histamine - act on the H2 receptor of parietal cell - increase HCl secretion

Question 21

What is paracrine signalling?

Answer 21

Cells enact a response through signalling on cells neighbouring them.close to it

Question 22

What does the paracrine system release to regulate acid secretion?

Answer 22

Histamine

Question 23

Describe the action of histamine on acid secretion

Answer 23

Act on H2 receptor of parietal cell - increase HCl secretion