FD

Reproductive System Summary

Sex Determination

  • Ovum (XX) + Sperm (XY) leads to Zygote.
  • SRY gene on Y chromosome determines sex.
    • Presence leads to testes development.
    • Absence leads to ovaries development.

Development of Sex Organs

  • SRY gene is the sex-determining region on the Y chromosome.
  • Homologous structures develop differently in males and females.

Male Reproductive System

  • Testes: Produce sperm (exocrine) and secrete testosterone (endocrine).
  • Interstitial cells: Targeted by LH to secrete testosterone.
  • Accessory glands contribute to seminal fluid: seminal vesicles, prostate gland, bulbourethral glands.
    • Seminal vesicles: Provide fructose, prostaglandins, and bicarbonate.
    • Prostate gland: Secretes milky fluid that activates sperm.
    • Bulbourethral gland: Produces alkaline mucus for lubrication.
  • Spermatogenesis: Sperm formation, begins at puberty.

Gametogenesis

  • Diploid chromosome number (2n): 46.
  • Haploid chromosome number (n): 23.
  • Spermatogenesis: Meiosis in males.
  • Spermiogenesis: production of spermatids

Hormonal Control in Males

  • GnRH from the hypothalamus stimulates the anterior pituitary to release FSH and LH.
  • FSH stimulates spermatogonia to produce sperm.
  • LH stimulates interstitial cells to release testosterone.
  • Testosterone enhances spermatogenesis and promotes secondary sex characteristics.

Female Reproductive System

  • Ovaries: Primary reproductive organ (gonad) in females.
  • Oogenesis: Egg production.
  • Females are born with about 2 million follicles, which decreases to 300,000–400,000 by puberty.

Oogenesis

  • Oogonia: Stem cells.
  • Primary oocyte: Arrested in meiosis I until ovulation.
  • Secondary oocyte: Arrested in meiosis II until fertilization.
  • Ovum: Mature oocyte, occurs only when fertilization finishes meiosis.

Ovarian Cycle

  • Regulated by FSH and LH.
  • Follicular phase: Follicle matures.
  • Luteal phase: Corpus luteum forms.
  • Ovarian cycle – 28-day cyclic changes within the ovaries
    • FSH and LH produce estrogen and progesterone.

Uterine Cycle

  • Caused by estrogen and progesterone.
  • Menstruation (Days 1–5): Endometrium disintegrates due to low hormone levels.
  • Proliferative phase (Days 6–13): Endometrium thickens due to estrogen.
  • Secretory phase (Days 15–28): Endometrium thickens and uterine glands mature due to progesterone.

Estrogen and Progesterone

  • Responsible for secondary sex characteristics and breast development.
  • Menopause: Ovarian cycle ceases, ovaries no longer respond to gonadotropic hormones.

Fertilization and Pregnancy

  • Zygote: Fertilized egg.
  • Embryo: Developing organism after mitosis.
  • Implantation: Embryo implants in the endometrial lining.
  • Only one sperm is needed to fertilize the egg, which is then called a zygote

Key Structures and Order

  • Sperm travel: Seminiferous tubules → Rete testis → Epididymis → Ductus deferens → Ejaculatory duct → Prostatic urethra → Membranous urethra → Spongy urethra → External urethral orifice.
  • Ovum travel: Ovary → Fimbriae of uterine tube → Infundibulum of uterine tube → Uterine tube → Uterus → Cervical canal → Vagina → Vaginal orifice.

Hormonal Effects

  • Male
    • LH: Targets interstitial cells; stimulates testosterone secretion.
    • FSH: Targets seminiferous tubules; stimulates spermatogenesis.
    • Testosterone: Development/maintenance of sex organs, secondary sex characteristics, spermatogenesis
  • Female
    • LH: Stimulates ovulation, formation of corpus luteum, progesterone secretion.
    • FSH: Stimulates follicle development, estrogen secretion.
    • Estrogen: Development/maintenance of sex organs, secondary sex characteristics, endometrial proliferation.
    • Progesterone: Prepares uterus for implantation, maintains pregnancy.