🧬

Overview of the Reproductive System

May 5, 2025

Chapter 27 - Reproductive System

Introduction

  • Primary sex organs (gonads):
    • Male: Testes
    • Female: Ovaries
  • Gonads produce gametes and secrete sex hormones.
  • Male function: Manufacture sperm and deliver to female tract for potential fertilization.
  • Fertilization: Sperm fuses with egg to form a zygote (first cell of new individual).

Objective 1: Describe the process of meiosis

  • Occurs in ovaries and testes; process for genetic makeup of eggs and sperm.
  • Human cells: 46 chromosomes (23 pairs of homologous chromosomes).
  • Meiosis vs Mitosis:
    • Mitosis: 1 DNA replication, 1 division, results in diploid cells.
    • Meiosis: 1 DNA replication, 2 divisions, results in 4 haploid cells.
  • Meiosis Steps:
    • Meiosis I: Reduction division, homologous pairs separate (diploid to haploid).
    • Meiosis II: Duplicates (sister chromatids) separate, forming 4 cells with 23 chromosomes each.
  • Genetic Variability:
    • Crossing over during Meiosis I.
    • Random lining up of homologous chromosomes.

Objective 2: Describe the process of spermatogenesis

  • Begins at puberty in testes; stem cells produce primary spermatocytes.
  • Process:
    • Spermatocytes move from outer edge of seminiferous tubule to lumen.
    • Meiosis I: Forms secondary spermatocytes.
    • Meiosis II: Forms spermatids.
    • Spermiogenesis: Spermatids elongate, shed cytoplasm, form a tail.
  • Sperm Structure:
    • Head: Genetic material.
    • Midpiece: Contains mitochondria.
    • Tail: Flagellum for propulsion.

Objective 3: Male reproductive organs and pathway of sperm

  • Testes:
    • Located in scrotum (3°C lower than body temp for sperm production).
    • Divided into lobules with seminiferous tubules for sperm production.
    • Leydig cells produce testosterone.
  • Pathway of Sperm:
    • From seminiferous tubules → epididymis (gain motility) → vas deferens → ejaculatory duct → urethra.
  • Accessory Glands:
    • Seminal vesicles produce alkaline fluid with fructose, enzymes, prostaglandins.
    • Prostate gland produces acidic fluid with nutrients and enzymes.
    • Bulbourethral glands produce mucus for urethra lubrication.
  • Erection and Ejaculation:
    • Erection: Blood influx into penile tissue, driven by nitric oxide.
    • Ejaculation: Sympathetic reflex, ducts contract, bladder sphincter constricts, penile muscles contract.
  • Hormonal Influence:
    • Hypothalamus stimulates FSH and LH production.
    • FSH: Stimulates spermatogenesis.
    • LH: Causes testosterone secretion.
    • Testosterone: Triggers sperm formation, secondary male characteristics.

Objective 4: Female reproductive organs and pathway of the egg

  • Ovaries: Produce eggs, estrogen, progesterone.
    • Follicles house oocytes.
    • Monthly, one follicle develops, releases egg (ovulation).
  • Pathway of Egg:
    • Ovulation: Egg released into peritoneal cavity.
    • Fimbriae and cilia move egg into uterine tube (site for potential fertilization).
    • Fertilized egg (zygote) or unfertilized egg moves to uterus.
  • Uterus:
    • Layers: Endometrium (inner), myometrium (muscular), perimetrium (outer).
    • Function: Receive, nourish, retain fertilized ovum.
  • Cervix and Vagina:
    • Cervix: Produces mucus, changes consistency mid-cycle.
    • Vagina: Acidic pH, protective but hostile to sperm.
  • Egg Supply and Hormonal Effect:
    • Females born with egg supply; eggs complete meiosis upon ovulation.
    • Estrogen promotes oogenesis, follicle growth, secondary female characteristics.

Objective 5: Describe the process of oogenesis

  • Before birth, stem cells form primary oocytes in primordial follicles.
  • Primary oocytes begin meiosis I, stall early.
  • Monthly, one primary oocyte resumes, ends meiosis I (forms secondary oocyte and first polar body).
  • Secondary oocyte begins meiosis II, halts at metaphase II.
  • If fertilized, completes meiosis II (yields ovum and second polar body).

Objective 6: Menstrual and ovarian cycles and hormones

  • Follicular Phase:
    • FSH and LH stimulate follicle growth, estrogen secretion.
    • Primordial follicle develops into Graafian follicle.
  • Ovulation:
    • Burst of LH releases oocyte (day 14).
  • Luteal Phase:
    • LH surge forms corpus luteum, secretes progesterone and estrogen.
    • If pregnancy: Corpus luteum persists, placenta takes over hormone production.
    • If no pregnancy: Corpus luteum degenerates, hormone levels fall.
  • Cycle Effects:
    • Progesterone prepares endometrium for implantation.
    • Menstruation occurs if no pregnancy.

Objective 7: Diseases of the Reproductive System

  • Gonorrhea: Caused by Neisseria gonorrhoeae, affects mucosal surfaces.
  • Syphilis: Caused by Treponema pallidum, primary sore to tertiary CNS lesions.
  • Genital Warts: Caused by human papillomavirus, linked to cervical cancer.
  • Genital Herpes: Caused by human herpes virus type 2, blister-like lesions.