Water-soluble hormones exhibit the shortest __________.

Correct Answer: A

Rationale: The correct answer is A: half-life. Water-soluble hormones have a shorter half-life compared to lipid-soluble hormones because they are quickly metabolized and excreted from the body. The other choices are incorrect because: B: Activation time is not directly related to the solubility of hormones. C: The size of the hormone molecule doesn't determine its solubility in water. D: The chain of amino acids may vary in different types of hormones, but it doesn't necessarily dictate their solubility.

Correct Answer: B

Rationale: The correct answer is B: Proximal part of dorsal pancreatic bud. The accessory pancreatic duct originates from the dorsal pancreatic bud during embryonic development. This is because the dorsal pancreatic bud gives rise to the body and tail of the pancreas, which includes the accessory pancreatic duct. The proximal part of the dorsal pancreatic bud specifically gives rise to the proximal part of the accessory pancreatic duct. Choices A, C, and D are incorrect because they refer to the distal part of the dorsal pancreatic bud, the distal part of the ventral pancreatic bud, and the proximal part of the ventral pancreatic bud, respectively, which are not associated with the origin of the accessory pancreatic duct.

Correct Answer: A

Rationale: Rationale: 1. T3, T4, and calcitonin are hormones secreted by the thyroid gland. 2. Thyroid gland is responsible for producing and releasing these hormones. 3. T3 and T4 regulate metabolism, while calcitonin helps regulate calcium levels. 4. Parathyroid glands secrete parathyroid hormone, not T3, T4, or calcitonin. 5. These hormones are not secreted in response to declining plasma levels of calcium. 6. T3, T4, and calcitonin are not steroids, they are peptide hormones. Therefore, the correct answer is A.

Correct Answer: A

Rationale: Step-by-step rationale: 1. The adrenal cortex is the outer layer of the adrenal gland that produces steroid hormones. 2. ACTH (adrenocorticotropic hormone) stimulates the adrenal cortex to secrete cortisol and aldosterone. 3. Therefore, the adrenal cortex is the target gland of ACTH, making choice A correct. Summary: A. Correct - The adrenal cortex is the target gland of ACTH. B. Incorrect - The adrenal medulla secretes catecholamines (e.g., adrenaline, noradrenaline). C. Incorrect - The sympathetic nervous system is responsible for the fight-or-flight response, not the adrenal cortex. D. Incorrect - ADH (antidiuretic hormone) and oxytocin are produced by the hypothalamus and released by the posterior pituitary gland, not the adrenal cortex.

Correct Answer: B

Rationale: The correct answer is B: Portal capillaries. The hypothalamus and adenohypophysis are connected by a system of blood vessels called the hypothalamic-pituitary portal system, which includes portal capillaries. These capillaries carry releasing and inhibiting hormones from the hypothalamus to the adenohypophysis to regulate the secretion of pituitary hormones. The other choices are incorrect because: A: Islets of Langerhans are clusters of cells in the pancreas involved in insulin and glucagon production, not connected to the hypothalamus or adenohypophysis. C: The corpus callosum is a structure that connects the two cerebral hemispheres and is not related to the hypothalamus or adenohypophysis. D: The medulla oblongata is part of the brainstem responsible for autonomic functions and is not involved in connecting the hypothalamus and adenohypophysis.