Free Reproduction MCQs with Answers

1. Spermatogenesis in the human male takes place in the

• A. seminiferous tubules
• B. epididymis
• C. prostate gland
• D. vas deferens

Explanation: The germinal epithelium lining the seminiferous tubules of the testis divides by mitosis and then meiosis to form spermatids, which mature into spermatozoa. The epididymis is where sperm are stored and gain motility after leaving the testis, so it is the tempting answer, but no division occurs there. The prostate and the vas deferens contribute secretions and transport, not gamete formation.

2. Testosterone is secreted by the

• A. Sertoli cells
• B. interstitial cells of Leydig
• C. germinal epithelium
• D. seminal vesicles

Explanation: The Leydig cells lie in the connective tissue between the seminiferous tubules and secrete testosterone in response to luteinising hormone from the anterior pituitary. Sertoli cells sit inside the tubules and nourish the developing sperm, which is why they are the usual confusion. Testosterone maintains sperm production and the secondary sexual characters such as voice and body hair.

3. Fertilisation of the human ovum normally occurs in the

• A. uterus
• B. cervix
• C. ampulla of the fallopian tube
• D. ovary

Explanation: The secondary oocyte is swept into the oviduct at ovulation and meets sperm in the wide upper third, the ampulla, within about a day. The zygote then divides as it travels down and reaches the uterus as a blastocyst several days later, so the uterus is the site of implantation rather than of fertilisation. Fertilisation in the ovary or in the abdominal cavity is possible but is an abnormal ectopic pregnancy.

4. The blastocyst implants itself in the

• A. myometrium
• B. perimetrium
• C. cervix
• D. endometrium

Explanation: The endometrium is the inner glandular lining of the uterus, thickened and richly supplied with blood by progesterone during the secretory phase, which is exactly what implantation requires. The myometrium is the thick smooth muscle layer whose contractions expel the baby at birth, and the perimetrium is the outer covering. Implantation in the cervix or oviduct is an ectopic pregnancy and is dangerous.

5. After ovulation the ruptured follicle becomes the corpus luteum, which mainly secretes

• A. progesterone
• B. FSH
• C. LH
• D. oxytocin

Explanation: Progesterone from the corpus luteum maintains the thickened endometrium and inhibits FSH and LH so that no further follicle ripens. FSH and LH are pituitary hormones acting on the ovary rather than products of it, which is the trap here. If no implantation occurs the corpus luteum degenerates after about ten days and progesterone falls, which brings on menstruation.

6. Ovulation is triggered by a sharp rise in

• A. oestrogen alone
• B. luteinising hormone
• C. progesterone
• D. follicle stimulating hormone

Explanation: Rising oestrogen from the ripening follicle switches the pituitary from negative to positive feedback and produces a sudden LH surge, which ruptures the follicle within about a day. Oestrogen is the signal that causes the surge rather than the trigger itself, which is why it is the tempting choice. Progesterone rises only after ovulation, once the corpus luteum has formed.

7. In a regular 28 day menstrual cycle, ovulation usually occurs on about day

• A. 5
• B. 8
• C. 21
• D. 14

Explanation: Ovulation falls near the midpoint of the cycle, roughly fourteen days before the next period begins, because the luteal phase is the fixed part at about fourteen days while the follicular phase varies. Day five is still within menstruation and day twenty one lies in the secretory phase, when the corpus luteum is already active. Counting backwards from the next expected period is the more reliable method in irregular cycles.

8. Menstruation begins when

• A. oestrogen rises sharply
• B. follicle stimulating hormone falls to zero
• C. the corpus luteum degenerates and progesterone falls
• D. the blastocyst implants in the uterine wall

Explanation: Without implantation the corpus luteum breaks down, progesterone withdrawal removes the support of the endometrium, its blood vessels constrict and the lining is shed as the menstrual flow. The falling progesterone also releases the pituitary from inhibition, so FSH rises again and the next cycle begins. Implantation has the opposite effect, since it keeps the corpus luteum alive and prevents menstruation.

9. The hormone detected by a standard urine pregnancy test is

• A. luteinising hormone
• B. follicle stimulating hormone
• C. progesterone
• D. human chorionic gonadotropin

Explanation: The chorion of the young embryo secretes hCG, which keeps the corpus luteum alive so that progesterone continues and the endometrium is not shed. Because only a pregnancy produces it, hCG is specific, whereas progesterone is high in the luteal phase of every cycle and so would give false positives. It appears in urine within about two weeks of fertilisation.

10. Which of the following is NOT a function of the placenta?

• A. Production of the fetus's red blood cells
• B. Exchange of oxygen and carbon dioxide
• C. Secretion of progesterone and hCG
• D. Transfer of nutrients from mother to fetus

Explanation: The fetus makes its own blood cells, first in the yolk sac and liver and later in the bone marrow, and maternal and fetal blood never actually mix in the placenta. What the placenta does is bring the two circulations close enough for exchange of gases, nutrients, wastes and antibodies, and it also works as an endocrine gland from about the third month. It further acts as a partial barrier, though alcohol, nicotine and many viruses cross it.