Braxton Hicks contractions are a sign

Correct Answer: B

Rationale: The correct answer is B: oxytocin. Braxton Hicks contractions are irregular, painless contractions of the uterus that occur throughout pregnancy. Oxytocin is the hormone responsible for stimulating contractions during labor. Therefore, the presence of Braxton Hicks contractions indicates the preparation of the uterus for labor under the influence of oxytocin. Choices A, C, and D are incorrect as they do not directly relate to the physiological mechanism of Braxton Hicks contractions.

Correct Answer: D

Rationale: The correct answer is D: 14 days. During oogenesis, the process of ovulation occurs approximately 14 days prior to the start of the next menstrual cycle. This is crucial for timing fertilization and pregnancy. The other choices are incorrect because: A: an ovum is the mature egg released during ovulation, not directly related to the menstrual cycle. B: 7 days is not a relevant timeframe in the context of oogenesis and menstrual cycles. C: a primary oocyte is the initial stage of egg development and needs further maturation before ovulation, not directly linked to the menstrual cycle timing.

Correct Answer: D

Rationale: The correct answer is D: Sertoli cells. Seminiferous tubules are lined with Sertoli cells, which provide structural support and nourishment to developing sperm cells. These cells also help in the process of spermatogenesis. A: Oocytes are female germ cells found in the ovaries, not in the seminiferous tubules. B: Red blood cells are not found in the seminiferous tubules. They are responsible for carrying oxygen in the bloodstream. C: Leydig cells are found in the interstitial tissue of the testes and are responsible for producing testosterone, not lining the seminiferous tubules. Therefore, the correct choice is D as Sertoli cells play a crucial role in sperm production within the seminiferous tubules.

Correct Answer: A

Rationale: The correct answer is A because oestrogen actually has a negative feedback effect on the hypothalamus. When oestrogen levels rise, it signals the hypothalamus to stop producing gonadotropin-releasing hormone (GnRH), which in turn decreases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) production. This negative feedback loop helps regulate the menstrual cycle. Choices B, C, and D are correct statements about oestrogen. Oestrogen does stimulate retention of fluid, growth of ovaries and follicles, and the development of female body characteristics.

Correct Answer: B

Rationale: The correct answer is B because oestrogen levels in females rise and fall every month in response to the menstrual cycle. This hormone is produced by the ovaries and plays a key role in regulating the menstrual cycle. During the menstrual cycle, oestrogen levels increase during the first half of the cycle (follicular phase), peak around ovulation, and then decrease in the second half of the cycle (luteal phase). This cyclical pattern is essential for preparing the uterus for potential pregnancy. Choices A, C, and D are incorrect because oestrogen levels do not follow a continuous decline throughout a female's life, peak during gestation, or reach their highest level just after birth.