Which hormone initiates and sustains labor contractions?

Correct Answer: D

Rationale: The correct answer is D: oxytocin. Oxytocin is the hormone responsible for initiating and sustaining labor contractions by stimulating the uterine muscles. It acts on the smooth muscle cells of the uterus to increase contractions. Estrogen (A) plays a role in preparing the uterus for labor but doesn't initiate contractions. HCG (B) is a hormone produced during pregnancy but is not directly involved in labor. Relaxin (C) helps relax the pelvic ligaments to facilitate childbirth, but it doesn't initiate contractions.

Correct Answer: D

Rationale: The correct answer is D because the ovaries produce secondary oocytes, which are released during ovulation for fertilization. Additionally, the ovaries produce estrogen and progesterone, which are essential for the menstrual cycle and reproductive health. Choice A is incorrect as primary oocytes are present before birth and insulin is produced by the pancreas. Choice B is incorrect because cortisol is produced by the adrenal glands, not the ovaries. Choice C is incorrect as tertiary oocytes do not exist, and insulin is produced by the pancreas.

Correct Answer: C

Rationale: The correct answer is C: Ovary. Line "C" is pointing to the ovary because it is the reproductive organ responsible for producing eggs and hormones in females. The ovary is located near the fimbriae and not the bladder or uterus. The fimbriae are finger-like projections near the ovary that help guide the released egg into the fallopian tube. The bladder is an organ unrelated to reproduction, and the uterus is a separate reproductive organ responsible for housing a developing fetus. Therefore, the correct choice is the ovary as it aligns with the function and location indicated by the diagram.

Correct Answer: A

Rationale: The correct answer is A: SRY. The Sex-determining Region Y (SRY) gene is the master switch for male development. It initiates the development of male gonads. Choice B, MIS, is a hormone involved in female reproductive development. Choices C and D, XYY and XXY, are genetic conditions related to male chromosomal variations and are not the master switch gene for male development.

Correct Answer: B

Rationale: The correct answer is B: Graafian follicle. Within the ovary, thousands of small sacs called follicles develop and grow, with one dominant follicle eventually maturing into a Graafian follicle. This structure contains the ovum (egg) and is released during ovulation. Ova (A) are the mature eggs released from the Graafian follicle. Corpus luteum (C) forms after ovulation and produces hormones to support pregnancy. Cysts (D) are abnormal fluid-filled sacs that can develop in the ovaries, different from the normal follicles.