Question

question 51 (0.5 points)
which of the following best describes the function of a gastric parietal cell?

1. secretes bicarbonate and intrinsic factor into the bloodstream during the gastric phase and uses the h⁺/k⁺ atpase pump to increase blood ph.
2. produces mucus to protect the stomach lining, releases hco₃⁻ through the hco₃⁻/cl⁻ antiporter, and secretes intrinsic factor during the intestinal phase.
3. releases pepsinogen and intrinsic factor during the cephalic phase of digestion, using the h⁺/k⁺ atpase pump to secrete hydrochloric acid into the stomach.
4. secretes hydrochloric acid (h⁺ and cl⁻) during the gastric and intestinal phases of digestion, using the h⁺/k⁺ atpase pump and releasing intrinsic factor to aid in vitamin b₁₂ absorption; also utilizes the hco₃⁻/cl⁻ antiporter to maintain acid - base balance.

Explanation:

To determine the correct function of gastric parietal cells:

1. Mucus production: Mucus is produced by mucous cells, not parietal cells, so options with mucus production are incorrect.
2. Pepsinogen release: Pepsinogen is released by chief cells, not parietal cells, so options mentioning pepsinogen release are incorrect.
3. Bicarbonate/intrinsic factor into blood: Parietal cells secrete HCl into the stomach (not bicarbonate/intrinsic factor into blood) and use \( \text{H}^+/\text{K}^+ \) ATPase for HCl secretion, not to increase blood pH.
4. Correct function: Parietal cells secrete HCl (via \( \text{H}^+/\text{K}^+ \) ATPase) during gastric/intestinal phases, release intrinsic factor for \( \text{B}_{12} \) absorption, and use \( \text{HCO}_3^-/\text{Cl}^- \) antiporter for acid - base balance.

Answer:

The option (the one with the blue background): Secretes hydrochloric acid (\( \text{H}^+ \) and \( \text{Cl}^- \)) during the gastric and intestinal phases of digestion, using the \( \text{H}^+/\text{K}^+ \) ATPase pump and releasing intrinsic factor to aid in vitamin \( \text{B}_{12} \) absorption; also utilizes the \( \text{HCO}_3^-/\text{Cl}^- \) antiporter to maintain acid - base balance.