Infarction of the bowel may be caused by:

Correct Answer: C

Rationale: Infarction of the bowel may be caused by a volvulus, where the bowel twists on its mesentery, leading to compromised blood flow. Mesenteric artery thrombosis can also cause bowel infarction by obstructing blood supply. Therefore, the correct answer is C (both). Choices A and B are incorrect because each of them individually can cause bowel infarction.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Gastric secretions contain intrinsic factor, essential for vitamin B12 absorption from the terminal ileum. 2. Intrinsic factor binds to vitamin B12 to facilitate its absorption. 3. Without intrinsic factor, vitamin B12 absorption is impaired, leading to pernicious anemia. 4. Therefore, choice B is correct. Summary: - Choice A is incorrect as gastric secretions increase, not decrease, when a person thinks of food. - Choice C is incorrect as hydrochloric acid (HCl) is secreted by parietal cells, not chief cells. - Choice D is incorrect as fat digestion primarily occurs in the small intestine with the help of pancreatic enzymes, not gastric secretions.

Correct Answer: A

Rationale: The correct answer is A: Amylase. Amylase is an enzyme that specifically breaks down carbohydrates into sugars in the mouth. It is produced by both salivary glands and pancreas. Protease (B) breaks down proteins, Lipase (C) breaks down fats, and Pepsin (D) breaks down proteins in the stomach. Therefore, A is the correct answer for the enzyme responsible for breaking down carbohydrates in the mouth.

Correct Answer: A

Rationale: The correct answer is A: mouth. Mechanical digestion begins in the mouth where food is chewed and mixed with saliva, breaking down into smaller pieces for easier swallowing and digestion. This process increases the surface area of food for enzymes to act upon. The stomach (B) primarily performs chemical digestion, the small intestine (C) is where most chemical digestion and absorption occur, and the large intestine (D) is mainly responsible for water absorption and formation of feces. Thus, the mouth is the correct choice for the beginning of mechanical digestion.

Correct Answer: D

Rationale: Rationale for Correct Answer D: - Psyllium is a bulk-forming laxative that works by absorbing water in the intestines, forming a gel-like mass that helps with bowel movements. - Taking large amounts of fluid is essential when using psyllium to prevent the gel-like mass from hardening and causing impaction or bowel obstruction. - Adequate fluid intake is crucial for the safe and effective use of psyllium as a laxative. Summary of Incorrect Choices: - Choice A is incorrect because fiber-containing laxatives like psyllium do not directly impact the absorption of fat-soluble vitamins. - Choice B is incorrect as dietary sources of fiber should not be eliminated entirely but rather balanced to prevent excessive gas. - Choice C is incorrect as all medications, including laxatives, can have potential adverse effects; however, psyllium is generally well-tolerated when used appropriately.