Reproductive System Vocabulary

Male Reproductive System

• Testes:
  • Seminiferous Tubules: Sperm production.
  • Interstitial Cells: Testosterone production.
• Scrotum:
  • Provides ideal temperature conditions for sperm formation; hangs outside the body.
• Epididymis:
  • Sperm maturation and storage.
  • Tubular storage site for sperm; hugs the lateral aspect of the testes.
• Ductus (Vas) Deferens:
  • Transports sperm from the epididymis to the ejaculatory duct.
  • Structure cut or cauterized during a vasectomy.
  • Joins epididymis to urethra.
• Prostate Gland:
  • Contributes to seminal fluid.
  • Surrounds the urethra at the base of the bladder; produces a milky alkaline fluid.
• Cowper's Glands (Bulbourethral Glands):
  • Contributes to seminal fluid.
  • Empties a lubricating mucus into the urethra.
• Seminal Vesicles:
  • Contributes to seminal fluid; contains sugar to nourish sperm.
  • Produces over half of the seminal fluid.
• Penis:
  • Organ that delivers semen to the female reproductive tract.
  • The male copulatory organ.
• Urethra:
  • Carries both sperm and urine.
  • Portion of the duct system that also serves the urinary system.

Path of Sperm

• Seminiferous Tubules → Rete Testis → Epididymis → Vas Deferens → Urethra.

Seminal Fluid Components

• Cowper's Glands: Lubricating mucus.
• Prostate Gland: Milky alkaline fluid.
• Seminal Vesicles: Sugar (nourishment).

Sperm Structure

• Tail (Flagellum): Movement.
• Midpiece: ATP (energy) production via mitochondria.
• Head: Contains DNA.
• Acrosome: Enzymes for egg penetration.

Testosterone

• Functions:
  • Maturation of reproductive organs/sperm development.
  • Secondary sex characteristics (hair, voice deepening, muscle mass, sex drive, wide shoulders, narrow waist).

Homeostatic Regulation of Testosterone

• Hypothalamus releases Gonadotropin-Releasing Hormone (GnRH).
• GnRH stimulates the anterior pituitary to release Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).
• LH stimulates interstitial cells in the testes to produce testosterone.
• FSH stimulates seminiferous tubules to produce sperm (and inhibin).
• High testosterone levels inhibit GnRH release.
• Inhibin inhibits GnRH release when sperm production is high.

Female Reproductive System

• Ovaries:
  • Follicles: Egg development and estrogen production.
  • Corpus Luteum: Progesterone and estrogen production.
• Oviducts (Fallopian Tubes):
  • Site of fertilization.
  • Transport of the egg to the uterus (aided by cilia).
  • Usual site of fertilization.
• Uterus:
  • Chamber that houses the developing fetus.
  • Location of fetal development.
• Endometrium:
  • Uterine lining.
• Cervix:
  • Opening to the uterus.
• Vagina:
  • Receives the penis during intercourse.
  • Birth canal.
  • The female organ of copulation.
• Clitoris:
  • Erectile tissue for sexual stimulation.
  • Homologous to male penis.

Estrogen

• Responsible for the proliferation phase of the endometrium.
• Responsible for the secondary sex characteristics of females.

Ovarian Cycle

• Follicular Phase (Days 0-14):
  • Follicle development stimulated by FSH.
  • Estrogen is produced by the developing follicle.
  • A spike in estrogen triggers a surge in LH, leading to ovulation.
• Ovulation (Day 14):
  • Egg release.
• Luteal Phase (Days 15-28):
  • Corpus luteum develops and produces progesterone and estrogen.
  • High progesterone levels inhibit LH and FSH release.
  • If no pregnancy, the corpus luteum degenerates, hormone levels drop, and the cycle repeats.

Uterine Cycle

• Menstruation:
  • Low hormone levels cause the uterine lining to shed.
• Proliferative Phase:
  • Estrogen causes the uterine lining to thicken.
• Secretory Phase:
  • Progesterone causes the uterine lining to thicken further and the glands to secrete mucus.

Hormonal Control of Ovarian and Uterine Cycles

• GnRH: Stimulates LH and FSH release.
• FSH: Promotes follicle growth and estrogen production.
• LH: Triggers ovulation; promotes the corpus luteum.
• Estrogen: Stimulates uterine lining growth; inhibits FSH release; is secreted by the follicle.
• Progesterone: Maintains uterine lining; inhibits LH and FSH release; it's secreted by the corpus luteum.

Hormonal Changes During Implantation

• Human Chorionic Gonadotropin (HCG) is produced.
  • HCG maintains the corpus luteum.
  • The corpus luteum produces progesterone.

Positive Feedback Mechanism

• Oxytocin during childbirth.

Key Terms

• Spermatogenesis: Process of producing male sex cells (sperm).
• Oogenesis: Process of producing female sex cells (eggs).
• Ovulation: Release of an egg.
• Fertilization: Sperm and oocyte unite.
• Zygote: Fertilized egg.
• Implantation: Zygote embeds into endometrial lining.

Additional Notes

• Sperm count per ejaculation: 300,000 - 400,000. They are designed for a short life, but move quickly.
• Number of eggs to mature: ~400 out of 2,000,000. It is not related to orgasm.
• Vas Deferens: ~ 6 meters long.

Hormones

• FSH: Promotes growth of ovarian follicles and production of estrogen.
• LH: Triggers ovulation.
• Estrogen and Progesterone: Inhibit follicle-stimulating hormone (FSH) release by the anterior pituitary.
• GnRH: Stimulates luteinizing hormone (LH) release by the anterior pituitary.