Parathormone receptors are expressed on the surface of:

Correct Answer: D

Rationale: The correct answer is D because parathormone receptors are expressed on the surface of osteoblasts, osteoclasts, and gut mucosal cells. Parathormone regulates calcium and phosphate levels in the body, influencing bone metabolism and intestinal absorption. Osteoblasts are bone-forming cells, osteoclasts are bone-resorbing cells, and gut mucosal cells are involved in calcium absorption. Therefore, parathormone receptors are present on all three cell types to coordinate calcium homeostasis. Choices A, B, and C are incorrect because parathormone receptors are not exclusive to any one cell type but are present on all three mentioned in the question.

Correct Answer: A

Rationale: The correct answer is A (1-2 months) because fertility typically returns quickly after stopping the combined estrogen-progestin contraceptive pill. Estrogen and progestin hormones are quickly metabolized and cleared from the body, allowing the menstrual cycle to resume within a month or two. Choice B (4-6 months) is incorrect as fertility usually returns sooner. Choice C (6-12 months) is also incorrect as it is an extended timeframe for fertility to return. Choice D (Uncertain period) is incorrect as there is a general understanding of the timeline for fertility to return after stopping the pill.

Correct Answer: A

Rationale: The correct answer is A: Long acting progestin. Injectable hormonal contraceptives typically contain progestin alone, as it suppresses ovulation and thickens cervical mucus. Estrogen is not commonly used in injectable contraceptives due to its higher risk of side effects like blood clots. Chorionic gonadotropin is not a component of injectable contraceptives and is typically used in fertility treatments. Therefore, choice A is correct as it aligns with the mechanism of action and formulation of injectable hormonal contraceptives.

Correct Answer: C

Rationale: The correct answer is C because progestin and estrogen work together to suppress ovulation by inhibiting the release of gonadotropins. Progestin thickens cervical mucus, making it hostile to sperm, while estrogen stabilizes the endometrium. Choices A and B are incorrect because the hormones don't block each other's side effects. Choice D is incorrect because it oversimplifies the mechanism of action.

Correct Answer: D

Rationale: Step-by-step rationale for choice D being correct: 1. Oral mifepristone is a progesterone receptor antagonist, leading to detachment of the pregnancy. 2. Oral misoprostol, a prostaglandin, causes uterine contractions and expulsion of the products of conception. 3. This regimen is safe, effective, and widely used for early pregnancy termination. 4. Choice A, B, and C involve different medications and routes not typically used for nonsurgical termination of early pregnancy.