Secretion of the acinar cells within the exocrine pancreas is not increased by:

Correct Answer: D

Rationale: The correct answer is D: Bicarbonate ions. Acinar cells in the exocrine pancreas are responsible for secreting digestive enzymes, which are stimulated by secretin, CCK, and parasympathetic stimulation. Bicarbonate ions, on the other hand, are secreted by ductal cells in the pancreas to neutralize the acidic chyme entering the small intestine. Therefore, an increase in bicarbonate ions would not directly affect the secretion of acinar cells. Secretin stimulates the release of bicarbonate ions, while CCK and parasympathetic stimulation trigger the release of digestive enzymes. So, choice D is the correct answer because it does not directly increase the secretion of acinar cells within the exocrine pancreas.

Correct Answer: B

Rationale: The correct answer is B: it is the function of parietal cells of the stomach. Parietal cells secrete hydrochloric acid in the stomach to aid in digestion. Chief cells are responsible for producing pepsinogen, not acid. Gastrin secretion actually stimulates acid secretion rather than inhibiting it, making choice C incorrect. Acetylcholine (Ach) also stimulates acid secretion, so choice D is incorrect. Parietal cells are the primary cells responsible for acid secretion in the stomach, making choice B the correct answer.

Correct Answer: A

Rationale: Rationale for Choice A: The center of defecation (Parasympathetic and anal reflexes) is in the sacral segments. In the defecation process, the sacral segments of the spinal cord play a crucial role in coordinating the parasympathetic and anal reflexes that control bowel movements. This is supported by the fact that damage to the sacral segments can lead to bowel dysfunction, such as in spinal cord injuries affecting these segments. The sacral segments are specifically responsible for regulating the relaxation of the internal anal sphincter and contraction of the rectum during defecation. Summary of Other Choices: B: Voluntary control of defecation is located in the medulla. This is incorrect as voluntary control of defecation is primarily regulated by higher brain centers, such as the cerebral cortex, and not in the medulla. C: The center for swallowing reflex is at the level of the spinal cord. This is incorrect as the center for the

Correct Answer: D

Rationale: Rationale: The Chief cell secretes pepsinogen, which is the inactive precursor of pepsin. Pepsinogen is later activated to pepsin by the acidic pH in the stomach. This process is essential for protein digestion. The other choices are incorrect because: A) Hydrogen and chloride ion secretion is mainly done by parietal cells, B) Pepsin is not secreted by Chief cells, and C) Gastrin is secreted by G cells, not Chief cells. Therefore, the correct answer is D.

Correct Answer: C

Rationale: The correct answer is C: Small intestine. The small intestine is where most of the absorption of nutrients, such as amino acids and fatty acids, occurs. This is because the small intestine contains villi and microvilli, which increase the surface area for absorption. Additionally, the small intestine secretes enzymes and bile to break down nutrients into smaller molecules for absorption. The stomach primarily aids in digestion, the large intestine absorbs water and electrolytes, and the esophagus is a passageway for food to reach the stomach.