The ovaries secrete which of the following hormones?

Correct Answer: A

Rationale: The correct answer is A: Oestrogen. Ovaries secrete oestrogen, a key female sex hormone involved in the development of secondary sexual characteristics, regulation of the menstrual cycle, and maintenance of pregnancy. Luteinising hormone (B) and follicle stimulating hormone (C) are secreted by the pituitary gland to regulate ovarian function. Oxytocin (D) is produced by the hypothalamus and released by the pituitary gland for uterine contractions and milk ejection, not by the ovaries. Therefore, A is correct as ovaries primarily produce oestrogen.

Correct Answer: A

Rationale: The correct answer is A because gastrin primarily stimulates gastric acid secretion and gastric mucosal growth but not insulin secretion. Gastrin acts on parietal cells to stimulate acid production and chief cells to release pepsinogen. Choice B and C are incorrect as gastrin does have a trophic effect on colonic and gastric mucosa, respectively. Choice D is also incorrect as gastrin stimulates pepsin secretion.

Correct Answer: D

Rationale: The correct answer is D because creatinine excretion is not depressed in starvation. Creatinine is a byproduct of muscle metabolism and is relatively constant even during starvation when muscle breakdown occurs. A: Incorrect, as increasing respiratory quotient > 1.0 indicates excessive carbohydrate utilization. B: Incorrect, SDA is the energy used for digestion and absorption of nutrients, not specific to protein metabolism. C: Incorrect, glucagon stimulates protein breakdown to release amino acids for energy during fasting.

Correct Answer: D

Rationale: Step 1: Activation of protein kinase A leads to phosphorylation of phosphorylase kinase. Step 2: Phosphorylase kinase phosphorylates and activates phosphorylase. Step 3: Active phosphorylase cleaves 1,4-glycosidic linkages in glycogen, not 1,6 linkages (eliminates A). Step 4: Phosphorylase is activated by phosphorylase kinase, not norepinephrine (eliminates B and C). Step 5: Inhibition of glycogen synthesis occurs when phosphorylase is activated, supporting choice D as the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Gonads. Gonads are the primary reproductive organs, responsible for producing sex hormones and gametes. In males, the testes produce testosterone and sperm, while in females, the ovaries produce estrogen and eggs. Adrenal glands (A) produce hormones like cortisol and adrenaline, which are not sex-specific. Parathyroid glands (C) regulate calcium levels in the body. Pancreas (D) produces insulin and digestive enzymes, unrelated to sex differences. Therefore, the secretion from gonads is the only one that differs between males and females due to their distinct reproductive functions.