Reproductive System Anatomy and Physiology

Male & Female Anatomy

  • Final Exam:
    • In-Person: May 6 @ 11:30 AM in Tukey Lecture Hall
    • Online: April 30 - May 6, Closes at 1:30 PM on May 6
    • Requires Respondus Lockdown
    • 100 Questions
      • 2/5 for Unit 4
      • 3/5 for Units 1-3

Reproductive System Comparison

  • Similarities:
    • Not necessary for survival
    • Develop from similar fetal tissue
    • System fully develops after puberty
    • Gonads (ovaries/testes) produce gametes (ova/sperm) and release sex hormones
  • Differences:
    • Time of function:
      • Female: ~30 years
      • Male: Throughout life
    • Gamete production:
      • Females: One ovum per month, produce ova during fetal development
      • Males: Produce 100,000,000 sperm/day after puberty
    • Cycling:
      • Female cycle controlled by hormones
      • Males do not cycle

Male Reproductive System

  • Major Divisions:
    • Testes
    • Accessory organs
    • Tubules
  • Scrotum:
    • Houses and separates testes
    • Layers: Epithelium, Raphe (seam at closure of fetal tissue), Muscle (Dartos & Cremaster muscles), Fascia
  • Testes:
    • Walnut-sized, form in body and descend
    • Site of spermatogenesis, produce androgens (testosterone)
    • Divided into lobules separated by septa
    • Connective tissue coatings: Tunica albuginea, Tunica vaginalis
  • Ducts:
    • Seminiferous tubules → Rete testis → Efferent ductules
  • Cells:
    • Sustentacular cells (caretakers, create blood-testis barrier)
    • Spermatogonia cells (form sperm)
    • Interstitial cells (between tubules)
    • Blood supply
  • Spermatic Ducts:
    • Carry sperm to outside
      • Epididymis: Highly coiled tube, site of sperm maturation (head, body, tail)
      • Ductus deferens: Passes through inguinal canal, behind bladder
      • Ejaculatory ducts: Connects to urethra
      • Urethra: Prostatic, Membranous, Penile
  • Accessory Glands:
    • Seminal vesicles: Posterior to bladder
    • Prostate gland: Inferior to bladder
    • Bulbourethral glands: In abdominal wall
  • Penis:
    • Erectile columns (tissue which fills with blood):
      • 2 corpora cavernosa (superior)
      • 1 corpus spongiosum (inferior, houses urethra)
    • Blood Supply: Dorsal artery/vein, Deep dorsal vein, Central arteries, Venous spaces
  • Connective Tissue Sheathes:
    • Tunica Albuginea, Deep Fascia, Superficial Fascia, Skin
  • External Regions:
    • Root (internal area): Bulb (corpus spongiosum connected to perineum), Crus (corpus cavernosa connected to pubic bone)
    • Body (external area)
    • Glans penis (contains urethral orifice)

Female Reproductive System

  • Ovaries:
    • Paired (~1.5 in x 1 in)
    • Supporting ligaments: Broad (binds to abdominal wall), Ovarian (binds to uterus), Suspensory (binds internal organs to abdominal wall)
  • Internal Structure:
    • Hilum: Entrance for ovarian vein and artery
    • Tunica albuginea: Connective tissue capsule
    • Medulla: Inner layer (blood vessels, lymph vessels, and nerves)
    • Cortex: Outer layer (contains ovarian follicles)
  • Follicles:
    • Primordial follicles: Present at birth
    • Primary follicles: Contain primary oocyte
    • Secondary follicles: Antrum (expanding fluid space)
    • Corpus luteum: Releases hormones (progesterone & estrogen)
    • Corpus albicans: If ovum not fertilized, corpus luteum disintegrates
  • Uterine Tubes:
    • Transport ova to uterus, site for fertilization
    • Structure: ~4 in long, Fimbriae
    • Layers: Mucosa (ciliated columnar epithelium), Muscularis, Serosa
  • Uterus:
    • Superior/posterior to bladder
    • Parts: Fundus, Body, Cervix
    • Suspensory ligaments: Broad, Round
  • Wall Layers:
    • Perimetrium: Outer connective tissue layer (visceral peritoneum)
    • Myometrium: Layers of smooth muscle
    • Endometrium: Inner layer sloughed off at menstruation
  • Vagina:
    • Muscular tube, Fornix
    • Three layers: Mucosa (stratified squamous tissue), Muscularis, Adventitia
    • Acidic secretions inhibit bacteria
  • Vulva:
    • Mons pubis
    • Labia majora (folds of skin)
    • Labia minora (smaller, internal folds, surround vestibule)
    • Vestibular glands
    • Urethra, Vagina
    • Clitoris (erectile tissue homologous to penis)

Male Physiology

  • Testes:
    • Seminiferous tubules: Spermatogenesis (receptor proteins for FSH in Sertoli cells).
    • Leydig cells: Secrete testosterone (receptor proteins for LH).
    • Scrotum: Maintains temperature 2-3°C below core temp (Dartus and Cremaster muscles).
  • Testosterone Secretion:
    • Initiation and maintenance of body changes in puberty.
    • Stimulates growth of muscles, larynx, and bone (until epiphyseal discs seal).
    • Promotes hemoglobin synthesis and spermatogenesis.
  • Estrogen Secretion:
    • Sertoli and Leydig cells secrete small amounts of estradiol.
    • May be responsible for negative feedback in brain, sealing of epiphyseal plates, and regulatory function in fertility.
  • Anterior Pituitary and Testes:
    • Hypothalamus releases GnRH → Anterior pituitary releases FSH and LH.
    • FSH stimulates Seminiferous tubules.(Sertoli cells) (Inhibin). LH stimulates Interstitial cells (Leydig) - Testosterone
      • Testosterone has negative feedback on the anterior pituitary.
  • Interactions Between Two Compartments of the Testes
    • FSH stimulates Spermatogenesis in the Seminiferous tubules. LH stimulates Interstitial (Leydig) cells.
    • Interstitial cells produce testosterone which has negative feedback on LH.
  • Spermatogenesis:
    • 64-72 days for sperm to mature.
    • Sertoli cells are important for sperm production.
    • Spermatogenesis: production of sperm (spermatozoa).
  • Sertoli Cells:
    • Blood-testes barrier: Tight junctions form barrier.
      • Prevents autoimmune destruction of haploid sperm and sperm antigens from escaping into blood.
  • Epididymis:
    • Nonmotile sperm enter, pass slowly through (~20 days), become motile.
    • Can be stored several months.
    • During ejaculation, epididymis contracts, expels sperm into ductus deferens.
  • Male Duct System:
    • Ducts carry sperm from testes to body exterior
      • Epididymis → Ductus deferens → Ejaculatory duct → Urethra (Prostatic, Membranous, & Penile)
  • Male Accessory Glands:
    • Produce Semen: Milky-white mixture of accessory gland secretions.
    • 2–5 ml semen are ejaculated containing 20–150 million sperm/ml.
  • Semen Characteristics:
    • Contains fructose (ATP production).
    • Alkaline fluid neutralizes acidity.
    • Contains prostaglandins (decrease viscosity of mucus in cervix) and hormone relaxin
    • Contains ATP for energy, clotting factors, and antibiotic chemicals.
    • Suppresses local female immune response.
  • Male Accessory Organs:
    • Epididymis: Sperm maturation, storage of sperm.
    • Seminal vesicles (2): Viscous alkaline fluid (fructose, citric acid, coagulating enzyme, prostaglandins).
      • Comprises 70% volume of semen.
    • Prostate secretes: Milky, slightly acid fluid (coagulation proteins, Citrate, enzymes).
      • One-third of semen volume.
    • Bulbourethral glands: Pre-ejaculatory alkaline fluid, lubricates glans penis and neutralizes acidic urine.
  • Erection, Emission, and Ejaculation:
    • Erection: Erectile tissue fills with blood, enlarges and becomes rigid.
      • Increased vasodilation of arterioles.
      • Blood flow into the erectile tissues of the penis.
    • Emission: Movement of semen into the urethra.
    • Ejaculation: Forcible expulsion of semen from the urethra out of the penis.
  • Penis - Prepuce:
    • Root and shaft that ends in glans penis.
    • Prepuce, or foreskin: Cuff of loose skin covering glans.
    • Circumcision: Surgical removal of foreskin.

Female Physiology

  • Oogenesis:
    • Production of female gametes takes years to complete.
    • Begins in fetal period, ovulation begins @ puberty.
    • @ 5 months gestation ovaries contain 6-7 million oogonia.
    • Apoptosis occurs: 2 million primary oocytes at birth, 400,000 primary oocytes at puberty.
    • 400 oocytes ovulated during the reproductive years.
  • Menstrual (fertility) Cycle:
    • 3 phases: Follicular Phase, Ovulation, Luteal Phase.
    • Duration approximately 28 days. Day 1 is the first day of menstruation.
  • Follicular Phase:
    • FSH (follicle-stimulating hormone) stimulates production of FSH receptors on granulosa cells.
      • Granulosa cells secrete estradiol. FSH and estradiol stimulate production of LH receptors in follicle.
    • Follicle matures: Fluid-filled antrum forms; follicle bulges from ovary surface.
    • Positive feedback: LH surge begins 24 hours before ovulation. Triggers ovulation.
  • Ovulation:
    • FSH causes follicle to grow large and thin-walled.
    • Triggers LH surge.
    • Wall of follicle ruptures (Day 14).
    • Ovulation: Ejection of oocyte from ripening follicle.
    • Corpus luteum develops from ruptured follicle after ovulation.
    • Fallopian (uterine) tubes: Ova drawn into the tube by cilia.