If you suck on a plain piece of bread, it will begin to taste sweet after a few moments. Saliva contains the digestive enzyme ______ which breaks down starch into ______.

Correct Answer: C

Rationale: The correct answer is C: amylase, maltose. Amylase is the digestive enzyme present in saliva that breaks down starch into maltose. When you suck on bread, the amylase in saliva starts breaking down the starch molecules into maltose, which is a sugar that tastes sweet. Option A is incorrect because amylase breaks down starch into maltose, not glucose. Option B is incorrect because pepsin is a stomach enzyme that breaks down proteins, not starch. Option D is incorrect because maltase is an enzyme in the small intestine that breaks down maltose into glucose, not the enzyme present in saliva.

Correct Answer: B

Rationale: The correct answer is B: bile canaliculi. Hepatocytes produce bile, which is then secreted into bile canaliculi within the liver. From there, bile flows into bile ducts and eventually reaches the gallbladder or small intestine. The other options are incorrect because bile is not secreted directly into the hepatic portal vein (A), hepatic sinusoid (C), or lacteal (D). The hepatic portal vein carries blood from the digestive organs to the liver, the hepatic sinusoid is a type of blood vessel within the liver, and lacteals are lymphatic vessels in the small intestine.

Correct Answer: D

Rationale: The correct answer is D because the parasympathetic nervous system is responsible for promoting rest and digest functions. The internal anal sphincter is controlled by the autonomic nervous system, specifically the parasympathetic division. When stimulated by the parasympathetic nervous system, the internal anal sphincter will relax, allowing for defecation to occur. A: The external anal sphincter is under voluntary control, not affected by the parasympathetic nervous system. B: The external anal sphincter contracts voluntarily, not influenced by the parasympathetic nervous system. C: The internal anal sphincter contracts under sympathetic stimulation, not parasympathetic.

Correct Answer: A

Rationale: The correct answer is A: Absorption and retention of water and electrolytes. Immediately after a meal, the body needs to absorb water and electrolytes to maintain proper hydration and electrolyte balance, crucial for survival. This process helps in nutrient absorption and maintaining overall body function. Reasons for why the other choices are incorrect: B: Elimination of toxins - While important for overall health, elimination of toxins is not the most critical function immediately after a meal for survival. C: Maintenance of barrier function - While important for protecting against harmful substances, it is not the most vital function immediately after a meal for survival. D: Extraction of maximum value from nutrients - While important for optimal nutrition, it is not as crucial as absorption and retention of water and electrolytes for immediate survival post-meal.

Correct Answer: D

Rationale: Step 1: Ghrelin is primarily produced by the stomach to stimulate appetite. Step 2: The pancreas produces insulin and enzymes, not ghrelin. Step 3: The adrenal glands produce hormones like cortisol, not ghrelin. Step 4: The liver is not a major site for ghrelin production, making choice D the correct answer.