Regarding the function of placenta

Correct Answer: B

Rationale: Step 1: The placental barrier is semi-permeable, allowing small molecules like oxygen and nutrients to pass but blocking larger molecules like antibodies. Step 2: IgG antibodies are the only type that can cross the placenta through active transport mechanisms. Step 3: This transfer provides passive immunity to the fetus. Step 4: Options A, C, and D are incorrect as the placenta has 4 main layers, progesterone does not induce preterm labor, and gas diffusion depends on concentration gradients, not pressure gradients.

Correct Answer: B

Rationale: The correct answer is B: seminal vesicle. Seminal vesicles produce fructose-rich fluid that serves as a nutrient source for sperm metabolism. This energy supply enables sperm to swim and undergo various metabolic processes. The other choices are incorrect because the prostate produces components of semen, Cowper's gland secretes pre-ejaculatory fluid, and the testes produce sperm cells but not the substrate for sperm metabolism. Thus, the seminal vesicle is the most direct source of the metabolic substrate for sperm.

Correct Answer: B

Rationale: The correct answer is B: broad ligament. The broad ligament is the largest ovarian ligament, providing support to the uterus and ovaries. It consists of layers of peritoneum and serves as a protective barrier. The other choices are incorrect because the ovarian ligament specifically connects the ovary to the uterus, the suspensory ligament supports the ovary and contains blood vessels, and the sacral ligament is not related to the ovary.

Correct Answer: D

Rationale: The correct answer is D: stratified squamous epithelium. This type of epithelium is found in the vagina to provide protection against abrasion and infection due to its multiple layers of cells. The stratified nature allows for wear and tear resistance. Simple cuboidal and columnar epithelia are not ideal for this function due to their single layer structure. Mucous epithelium is not a recognized epithelial type.

Correct Answer: C

Rationale: The correct answer is C: estrogens. Estrogens inhibit their own secretion through negative feedback. When estrogen levels rise, they signal the hypothalamus and pituitary gland to decrease the production of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), ultimately leading to a decrease in estrogen secretion. This self-regulation maintains hormonal balance in the body. Incorrect choices: A: FSH - FSH stimulates the production of estrogen by the ovarian follicles, so it does not inhibit estrogen secretion. B: LH - LH also plays a role in stimulating estrogen production and does not inhibit its secretion. D: Progesterone - Progesterone is involved in the menstrual cycle and pregnancy but does not directly inhibit estrogen secretion.