The pharyngeal phase of swallowing includes:

Correct Answer: D

Rationale: The correct answer is D because the pharyngeal phase of swallowing involves the contraction of the pharyngeal constrictors, which propel the bolus of food or liquid down the pharynx towards the esophagus. This muscular contraction helps in the proper movement of the swallow. A, a deep breath, is not part of the pharyngeal phase but may precede swallowing. B, elevation of the tongue against the hard palate, is part of the oral phase of swallowing, not the pharyngeal phase. C, contraction of the upper esophageal sphincter, occurs in the esophageal phase, not the pharyngeal phase.

Correct Answer: B

Rationale: The correct answer is B: lower gastrointestinal bleeding. Hematochezia refers to the passage of bright red blood in the stool, typically originating from the lower gastrointestinal tract. Upper gastrointestinal bleeding would present as melena (dark, tarry stool). Choice A is incorrect as hematochezia does not indicate upper GI bleeding. Choice C is incorrect because hematochezia specifically points to lower GI bleeding. Choice D is incorrect as hematochezia is associated with lower GI bleeding.

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.