Gastric secretions:

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: 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.

Correct Answer: D

Rationale: The correct answer is D because esomeprazole (Nexium) is a proton pump inhibitor that works by decreasing stomach acid production, thereby treating gastroesophageal reflux disease. This explanation is important for the patient to understand the mechanism of action of the medication. Choice A is incorrect because esomeprazole does not increase the rate of gastric emptying; instead, it reduces acid production. Choice B is incorrect because esomeprazole does not neutralize stomach acid immediately; it takes a few days to reach its full effect. Choice C is incorrect because esomeprazole does not coat and protect the stomach and esophagus; it works by reducing acid production. In summary, the correct answer is D because it accurately describes how esomeprazole works to manage recurring heartburn by decreasing stomach acid production, which is essential for treating gastroesophageal reflux disease.

Correct Answer: B

Rationale: The correct answer is B: pyloric valve. The pyloric valve is located between the stomach and the small intestine, specifically at the junction of the stomach and the duodenum. Its main function is to regulate the flow of partially digested food from the stomach into the small intestine. This control is crucial to ensure that the small intestine receives food at a manageable rate for optimal digestion and absorption of nutrients. The cardiac sphincter (A) is located at the entrance of the stomach from the esophagus and prevents acid reflux. The ileo-colic valve (C) is located between the small and large intestines, controlling the flow of contents between them. The sphincter of Oddi (D) regulates the flow of bile and pancreatic juice into the small intestine.