Insufficient Levels of Thyroid Hormone in Adults Cause-------------

Correct Answer: C

Rationale: The correct answer is C: Myxedema. Insufficient levels of thyroid hormone in adults lead to myxedema due to decreased metabolism and energy production. Goiter (A) is the enlargement of the thyroid gland, not caused by low thyroid hormone levels. Tetany (B) is muscle spasms due to low calcium levels, not related to thyroid hormone deficiency. Cretinism (D) is a condition of severe hypothyroidism in infants, not in adults. Therefore, the correct choice is C as it directly relates to the consequences of low thyroid hormone levels in adults.

Correct Answer: B

Rationale: The correct answer is B: increased gastric motility and emptying. Cholecystokinin (CCK) is a hormone that primarily functions to stimulate gallbladder contraction (A), secretion of pancreatic juice (D), and inhibit gastric motility and emptying. Choice C, glucagon secretion, is not directly related to the actions of CCK. The incorrect choices (A, C, D) are all actions associated with CCK, while choice B goes against the typical action of CCK on gastric motility.

Correct Answer: A

Rationale: The correct answer is A: short chain fatty acids. Short chain fatty acids are primarily absorbed in the colon through passive diffusion. The colon plays a crucial role in absorbing these fatty acids due to its high concentration of beneficial gut bacteria that break down dietary fiber into short chain fatty acids. Calcium is mainly absorbed in the small intestine, vitamin K is absorbed in the small intestine and partially in the colon, and oligosaccharides are mainly broken down by enzymes in the small intestine.

Correct Answer: D

Rationale: The correct answer is D because blood from the islets of Langerhans drains into the hepatic portal vein. This is important for the regulation of blood glucose levels by allowing insulin and glucagon produced by the islets to reach the liver directly. Choice A is incorrect because D cells secrete somatostatin, not pancreatic polypeptide. Choice B is incorrect as beta cells, not A cells, are the most common in the islets. Choice C is incorrect as the islets are most plentiful in the tail of the pancreas.

Correct Answer: C

Rationale: The correct answer is C because the substrates of the flavoprotein-cytochrome system are pyruvate, water, oxygen, and ATP. Pyruvate is oxidized to produce energy in the form of ATP, water is a byproduct of the electron transport chain, and oxygen is the final electron acceptor. Choices A and B are incorrect because cytochrome oxidase is not the first step in the chain, and the system does not occur within the endoplasmic reticulum. Choice D is incomplete.