GI secretion and digestion

Question 1

1. List the functions of secreted gastric acid.

Answer 1

kill bacteria, start digestion by triggering release of pepsin

Question 2

2. Describe the protective mechanisms in place to limit toxicity of gastric acid, including occasions where these processes might be disrupted.

Answer 2

mucosal barrier and bicarbonate secretion

Question 3

3. Discuss the modulation of gastric acid secretion throughout the day and night.

Answer 3

Inter digestive phase-follows a circadian rhythm, lowest in the am, before awakening and highest in the evening

Cephalic phase-mostly neural regulation
Gastric phase- initially neural followed by endocrine and neural

Intestinal phase- mostly endocrine

Question 4

4. In general terms, describe how the three parietal cell secretagogues induce acid secretion.

Answer 4

Ach coming from parasymp activate ECL cells which release histamine which act on parietal cells
Ach acts directly on parietal cells M3 receptor
gastrin receptor

Question 5

5. Describe the mechanism of gastric acid generation and secretion, including the role of K+, Cl /HCO3, carbonic anhydrase and H+-K+ ATPase.

Answer 5

cl- bicrab exchanger on basal lateral surface brings cl in, carbonic anhydrase takes CO2 and hydroxide to make H+ and H2O and Bicarb. H+/K+ ATPASE is highly energy requiring and drives gradient.

Question 6

7. Describe the role of the stomach, if any, on the gastric digestion of carbohydrates, proteins, and fats.

Answer 6

stomach can start the digestion of amino acids