Following a diagnosis of Zollinger-Ellison syndrome, a 70-year-old woman undergoes gastrectomy. Her physician informs her that she will require lifelong intramuscular vitamin B12 injections. Which specific type of cells' absence is responsible for the need for vitamin replacement?

Correct Answer: D

Rationale: Parietal cells produce intrinsic factor, necessary for vitamin B12 absorption; their absence after gastrectomy necessitates B12 injections.

Correct Answer: B

Rationale: Pepsin is secreted into the stomach as pepsinogen by chief cells and activated by stomach acid. It does not digest the stomach due to the protective mucus layer.

Correct Answer: B

Rationale: Lipase hydrolyzes triglycerides into fatty acids and glycerol, which are then absorbed.

Correct Answer: C

Rationale: Receptors detect changes in the internal environment as the first step in homeostasis.

Correct Answer: A

Rationale: Bowman's capsules, part of the nephron, are located in the renal cortex.