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🫀 Science · Human Anatomy and Physiology · Lesson 11 of 12 · 6 min

Reproductive systems: anatomy, gametes and the menstrual cycle

🧬 Two very different systems share one goal: get a haploid sperm and a haploid egg together. The TEAS asks where each is made, which hormones run the cycle, and where fertilization happens.

💡 Key idea

FSH grows the follicle, estrogen builds the lining, an LH surge causes ovulation, progesterone keeps the lining, and fertilization happens in the uterine tube.

🧠 The idea

In males, sperm are made in the seminiferous tubules of the TESTES, mature and are stored in the epididymis, then travel the vas (ductus) deferens and ejaculatory duct to the urethra. The seminal vesicles, prostate and bulbourethral glands add fluid to form semen. In females, the OVARIES make eggs (oocytes) and hormones; the uterine (fallopian) tube carries the egg to the uterus, which opens through the cervix into the vagina. GAMETOGENESIS uses meiosis to make haploid cells (23 chromosomes): spermatogenesis yields four sperm per cell, oogenesis yields one egg plus polar bodies. The MENSTRUAL cycle averages 28 days. FSH from the anterior pituitary grows a follicle, which makes estrogen and thickens the uterine lining. A surge of LH triggers ovulation near day 14. The leftover corpus luteum makes progesterone to keep the lining ready. Fertilization normally occurs in the uterine tube; without it, progesterone falls and menstruation begins.

✏️ Worked example

Trace a sperm from production to exit. Step 1: made in the seminiferous tubules of the testis. Step 2: matures in the epididymis. Step 3: travels up through the vas deferens. Step 4: joins seminal vesicle fluid at the ejaculatory duct. Step 5: leaves through the urethra. Order: seminiferous tubules, epididymis, vas deferens, ejaculatory duct, urethra. Note that the urethra is shared with the urinary system in males but not in females.

📌 Takeaways

  • Testes make sperm and testosterone; ovaries make eggs, estrogen and progesterone.
  • Meiosis makes haploid gametes; fertilization restores the diploid number (46).
  • LH surge → ovulation; corpus luteum → progesterone; fertilization in the uterine tube.

✅ Check yourself

Question 1 of 3

Where are sperm stored while they mature?

  1. Prostate gland
  2. Seminal vesicle
  3. Epididymis
  4. Vas deferens
Show the answer and rationale

Answer: C

Sperm mature and are stored in the coiled epididymis on the back of each testis. The seminal vesicles and prostate add fluid to semen, and the vas deferens is the duct that carries sperm onward during ejaculation.

Question 2 of 3

Which hormone surge directly triggers ovulation?

  1. Follicle-stimulating hormone
  2. Oxytocin
  3. Luteinizing hormone
  4. Progesterone
Show the answer and rationale

Answer: C

A mid-cycle surge of luteinizing hormone (LH) from the anterior pituitary causes the mature follicle to release its egg. FSH grows the follicle earlier, progesterone rises after ovulation, and oxytocin acts in labor and milk letdown.

Question 3 of 3

Where does fertilization of an egg normally take place?

  1. Cervix
  2. Uterine (fallopian) tube
  3. Ovary
  4. Uterus
Show the answer and rationale

Answer: B

Sperm usually meet the egg in the outer part of the uterine tube, and the early embryo then travels to the uterus to implant. The ovary releases the egg, and the cervix is only a passage.

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