Where are most digestive enzymes activated?

Correct Answer: B

Rationale: The correct answer is B: small intestine. Digestive enzymes are activated in the small intestine to break down nutrients. Firstly, enzymes are secreted by the pancreas into the small intestine, where they act on carbohydrates, proteins, and fats. Secondly, bile from the liver helps in the digestion of fats. The stomach mainly secretes gastric juices for protein digestion, not enzymes for overall digestion. The liver produces bile, not digestive enzymes. The pancreas secretes various digestive enzymes, but they become activated in the small intestine.

Correct Answer: C

Rationale: The correct answer is C because the defecation reflex is integrated in a control center in the sacral spinal cord. This is due to the presence of the parasympathetic nerves that control the smooth muscles of the colon and rectum in the sacral region. The sacral spinal cord is responsible for coordinating the reflexive relaxation of the internal anal sphincter and contraction of the rectum during defecation. Choices A and B are incorrect because the initiation and integration of the defecation reflex do not involve the anal canal stretching or the lumbar spinal cord. Choice D is incorrect as the defecation reflex is not controlled by the vagus nerve, which is primarily responsible for the parasympathetic innervation of organs in the thorax and upper abdomen.

Correct Answer: C

Rationale: The correct answer is C: Lactase. Lactase is an enzyme produced in the small intestine, not in the pancreas. The exocrine pancreas secretes digestive enzymes like chymotrypsinogen, proelastase, and lipase to aid in the digestion of proteins, fats, and carbohydrates. Lactase is responsible for breaking down lactose, a sugar found in dairy products, and is produced in the small intestine. Therefore, C is the correct answer. Choices A, B, and D are incorrect because chymotrypsinogen, proelastase, and alph are all enzymes produced by the pancreas to aid in digestion.

Correct Answer: D

Rationale: The correct answer is D because G cells in the gastric pit secrete gastrin, not histamine. Gastrin stimulates the release of hydrochloric acid in the stomach. Mucous cells are not enteroendocrine, so A is incorrect. G cells are not exocrine, making B incorrect. D cells secrete somatostatin, not histamine, so C is also incorrect.

Correct Answer: C

Rationale: The correct answer is C because carcinoid syndrome can occur with carcinoid tumors of the appendix and ileum. Carcinoid tumors of the appendix can lead to carcinoid syndrome due to the release of serotonin and other vasoactive substances. Similarly, carcinoid tumors localized to the ileum can also produce these substances, leading to the development of carcinoid syndrome. Choices A and B alone are not comprehensive enough as both sites can give rise to carcinoid syndrome. Choice D is incorrect as carcinoid syndrome can indeed occur with tumors from both sites.