The hormone that stimulates uterine contractions is

Correct Answer: A

Rationale: The correct answer is A: oxytocin. Oxytocin is the hormone responsible for stimulating uterine contractions during labor and childbirth. It is produced by the pituitary gland and plays a crucial role in the initiation and progression of labor. Estrogen (B) and progesterone (D) are involved in the menstrual cycle and pregnancy maintenance but do not directly stimulate uterine contractions. Granular cell carcinoma (C) is a type of cancer and not a hormone related to uterine contractions.

Correct Answer: A

Rationale: Step 1: Newborn infants have limited hepatic capacity to store and synthesize glycogen and glucose. Step 2: This limited capacity results in the plasma glucose concentration not being maintained in a normal range for more than a few hours after feeding. Step 3: Feeding every few hours ensures a constant supply of glucose to maintain plasma glucose levels. Step 4: Thus, it is important to feed newborn infants every few hours to prevent hypoglycemia. Summary: A: Correct - Maintaining plasma glucose levels due to limited hepatic capacity. B: Incorrect - Protein concentration is not the primary concern for feeding frequency. C: Incorrect - Keeping food in the stomach constantly does not improve gastrointestinal function. D: Incorrect - Hypoproteinemic edema is not the primary reason for feeding frequency.

Correct Answer: D

Rationale: The correct answer is D: Abnormally high levels of testosterone in the maternal blood. This can cause virilization of the female fetus, leading to the development of male external genitalia. Testosterone exposure during fetal development can result in the formation of a penis and scrotum without testes in a genetic female (XX). Rationale: 1. Testosterone is responsible for the development of male external genitalia. 2. XX chromosomes indicate a genetic female. 3. Lack of testes indicates incomplete masculinization. 4. High levels of testosterone can override the default female development pattern. Other choices are incorrect because: A: Human chorionic gonadotropin does not directly affect fetal genital development. B: Estrogen is not responsible for male genital development. C: Luteinizing hormone does not directly influence the development of external genitalia in the fetus.

Correct Answer: D

Rationale: Step 1: The trophoblast cells of the blastocyst invade the endometrial lining during implantation. Step 2: The trophoblast cells secrete enzymes to digest the nutrient-rich endometrial cells. Step 3: The digested nutrients are absorbed by the trophoblast cells. Step 4: These nutrients are then utilized by the blastocyst for its growth and development. Step 5: This process ensures that the blastocyst receives the necessary nutrition for the first week after implantation. Summary: A: Incorrect. Endometrial secretions are no longer the source of nutrition after implantation. B: Incorrect. While the blastocyst may contain some stored nutrients, they are not sufficient for the first week post-implantation. C: Incorrect. The placenta is not fully functional until later in pregnancy, so it does not provide nutrition in the first week.

Correct Answer: B

Rationale: The correct answer is B, after ovulation in a female. After ovulation, the ruptured follicle transforms into a corpus luteum, which secretes progesterone to support the uterine lining. Prior to ovulation (choice A) there is a mature follicle, not a corpus luteum. Choice C is incorrect as the corpus luteum is a structure in the female reproductive system, not present in semen. Choice D is incorrect as the corpus luteum persists for about 14 days after ovulation, not just on the day of ovulation.