The submucosa of the GIT

Correct Answer: B

Rationale: The submucosa of the GIT is rich in blood vessels, nerves, and lymphatic vessels, aiding in absorption and secretion of nutrients and fluids. The submucosa is not primarily responsible for protection (choice A). It does not contain distinct outer and inner layers (choice C). The submucosa is located between the mucosa and muscularis externa, not the serosa (choice D). Therefore, the correct answer is B as it aligns with the known functions and characteristics of the submucosa.

Correct Answer: A

Rationale: The correct answer is A because Clostridium difficile produces toxins, specifically enterotoxins, which cause damage to the intestinal mucosa leading to pseudo-membranous colitis. The organism colonizes the colon and then elaborates the toxins, which disrupt the mucosal barrier. Choice B is incorrect as there is no preformed toxin ingested; the toxin is produced by the organism after colonization. Choice C is incorrect as Clostridium difficile does not invade and destroy the mucosa directly. Choice D is incorrect as the host immune response is a consequence of the toxin production, not the primary mechanism of disease.

Correct Answer: B

Rationale: The correct answer is B: Gastrin stimulates HCL secretion. Gastrin is a hormone released from the stomach, not the duodenum. It acts to increase the secretion of hydrochloric acid (HCL) in the stomach, aiding in digestion. Gastrin also accelerates stomach emptying, contrary to choice C. Therefore, options A and C are incorrect. Choice D is incorrect as well because only option B is correct.

Correct Answer: C

Rationale: The correct answer is C: Bile salts are produced by the liver from cholesterol. Rationale: 1. Bile salts aid in the emulsification and digestion of fats, not proteins (A). 2. Pancreatic amylase is responsible for carbohydrate digestion, not bile salts (B). 3. The liver synthesizes bile salts from cholesterol to facilitate fat digestion and absorption (C). 4. Bile salts reduce lipid surface tension to form micelles, aiding in fat digestion, rather than increasing it (D).

Correct Answer: A

Rationale: The correct answer is A because salivary secretion contains enzymes like amylase that start the digestion of carbohydrates in the mouth. This enzyme breaks down complex carbohydrates into simpler sugars. Choices B, C, and D are incorrect because salivary secretion is not directly controlled by secretin hormone, does not start the digestion of proteins, and is not highly acidic. Salivary secretion primarily aids in the initial breakdown of carbohydrates, preparing them for further digestion in the stomach and intestines.