Which type of cell in the stomach secretes hydrochloric acid?

Correct Answer: A

Rationale: The correct answer is A: parietal cells. Parietal cells are the specific type of cell in the stomach responsible for secreting hydrochloric acid. They play a crucial role in the digestion process by creating an acidic environment necessary for the activation of digestive enzymes and breakdown of food. Chief cells mainly produce pepsinogen, mucous cells secrete mucus for protection, and enteric cells are related to the enteric nervous system, not acid secretion in the stomach. Therefore, parietal cells are the correct choice for this question.

Correct Answer: B

Rationale: The correct answer is B because the small intestine is primarily responsible for absorbing nutrients from digested food. It has specialized structures like villi to maximize nutrient absorption. Choice A is incorrect as the pancreas and other organs produce digestive enzymes. Choice C is incorrect as the liver produces bile. Choice D is incorrect as waste is stored in the large intestine, not the small intestine.

Correct Answer: C

Rationale: The correct answer is C: CCK. Cholecystokinin (CCK) is a hormone released by the small intestine in response to the presence of fatty acids and amino acids. It stimulates the release of bile from the gallbladder and increases bile production by the liver cells to aid in digestion. Sympathetic activation (choice A) typically inhibits digestive functions. Secretin (choice B) primarily stimulates pancreatic bicarbonate secretion, not bile production. Bile salts (choice D) are products of bile, not direct stimulators of bile production. Therefore, CCK is the correct choice as it directly influences the production of bile by the liver cells.

Correct Answer: D

Rationale: The correct answer is D: Mainly found in the colon. Intestinal flora, also known as gut microbiota, is primarily located in the colon. This is because the colon provides an ideal environment for the growth and survival of the diverse array of beneficial bacteria that make up the intestinal flora. These bacteria play a crucial role in various physiological functions, such as digestion, immune system regulation, and vitamin production. Choices A, B, and C are incorrect because intestinal flora are predominantly bacteria (not viruses), are not solely located in the duodenum but throughout the gastrointestinal tract, and are essential for normal digestion, not just needed.

Correct Answer: A

Rationale: Saliva contains an enzyme called amylase, which helps break down sucrose (a type of sugar) into glucose and fructose for digestion. Therefore, the correct answer is A. Saliva does not play a significant role in the digestion of phospholipids (B), speaking ability (C), or breaking food down into small pieces (D).