WEEK 12 NOTES ANATOMY

Page 1: General Overview of Reproductive System

• The reproductive system does not contribute to homeostasis.
• Essential for the continuation of the species but dispensable for individual survival.
• Primary sex organs (gonads):
  • Testes (males): Produce sperm and secrete androgens.
  • Ovaries (females): Produce ova and secrete estrogens and progesterone.
• Accessory organs: Ducts, glands, and external genitalia.

Page 2: Male Reproductive System Structure and Pathway

• Testes: Gonads located within the scrotum produce sperm.
• Duct system:
  • Epididymis → Ductus deferens → Ejaculatory duct → Urethra.

The Scrotum

• Sac of skin outside the abdominopelvic cavity maintaining temperature 3°C below body temperature (essential for sperm production).
• Muscles:
  • Dartos muscle: Wrinkles scrotal skin.
  • Cremaster muscles: Elevate testes.

The Testes

• Surrounded by:
  • Tunica vaginalis: Outer layer
  • Tunica albuginea: Inner fibrous capsule.
• Divided into lobules, each containing 1–4 seminiferous tubules (sperm factories).
• Interstitial endocrine cells (Leydig cells): Produce androgens.

Important Testicular Cells

1. Spermatogonia:
   • Undergo mitosis to replenish sperm stock.
2. Leydig Cells:
   • Produce testosterone, DHT, DHEA.
3. Sertoli Cells:
   • Support sperm, create blood-testis barrier, secrete inhibin B and ABP.

Page 3: Male Duct System

Epididymis

• Approximately 6 meters long.
• Absorbs testicular fluid and provides nutrients.
• Nonmotile sperm mature here over time; contracts during ejaculation to propel sperm.

Ductus Deferens (Vas Deferens)

• Carries sperm to the ejaculatory duct; joins seminal vesicle to form ejaculatory duct.
• Vasectomy: Cutting ductus deferens allows effective birth control.

Urethra

• Carries urine and sperm (at different times).
• Divisions:
  • Prostatic urethra
  • Membranous urethra
  • Spongy (penile) urethra.

Accessory Glands

Page 4: Semen Composition

• Milky-white mixture of sperm and glandular secretions.
• Volume: 2–5 mL semen, 20–150 million sperm/mL.
• Components:
  • Fructose (for ATP production)
  • Alkalinity (neutralizes acidity)
  • Relaxin and enzymes (enhance motility)
  • Prostaglandins (reduce cervical mucus viscosity)
  • Antibacterial factors
  • Clotting factors (later broken down by fibrinolysin).

Male External Genitalia and Sexual Response

Erection

• Erectile tissues fill with blood:
  • Corpus spongiosum: Surrounds urethra.
  • Corpor cavernosa: Paired structures.
• Parasympathetic stimulation: Causes NO release → smooth muscle relaxation → arterioles dilate → blood fills tissues.

Page 5: Ejaculation and Erectile Dysfunction

Ejaculation

• Sympathetic spinal reflex involves:
  • Internal urethral sphincter contracts (to prevent urine mixing).
  • Ducts and glands contract.
  • External urethral sphincter relaxes.
  • Bulbospongiosus muscles contract, expelling semen at approximately 5 m/s (~10 mph).

Viagra and Sexual Response

• Erectile dysfunction: Often due to decreased NO production.
• Viagra: Enhances cGMP action → prolongs erection.
• Warning: Seek help if erection lasts > 4 hours.

Page 6: Female Reproductive System Structures

• Ovaries: Produce ova, estrogen, and progesterone.
• Other structures:
  • Uterine tubes (fallopian tubes), Uterus, Vagina, Vulva, Clitoris.

Vagina

• Extends from cervix to exterior and serves multiple functions:
  • Receives penis
  • Birth canal
  • Contains hymen (membrane partially covering vaginal opening).

Vulva and Clitoris

• Vulva: External genitalia including:
  • Bartholin’s glands (lubricate).
  • Paraurethral glands (female prostate).
• Clitoris: Rich in somatosensory nerves, consists of erectile tissue (corpus cavernosum).

Page 7: Uterus and Its Layers

Uterus

• Regions:
  • Cervix: Connects to vagina.
  • Body: Main part of the uterus.
  • Fundus: Superior region.
• Functions: Receives, retains, and nourishes fertilized egg.

Uterine Wall Layers

Uterine Tubes (Fallopian Tubes)

• Site of fertilization; fimbriae sweep oocyte into tube; peristalsis moves oocyte toward uterus; oocytes may be lost in the peritoneal cavity.

Page 8: Pre-Embryonic Stage and Pregnancy

Pre-Embryonic Stage: Cleavage

• Stages of Development:
  • Zygote → Morula (solid ball) → Blastocyst (hollow ball) → Gastrula (invaginated ball).

Pregnancy and Trimesters

• Pregnancy length: Approximately 40 weeks (38 weeks post-fertilization).
• Three trimesters:
  • Pre-embryonic (Weeks 1–2)
  • Embryo (Weeks 3–8)
  • Fetus (Weeks 9–40).

Page 9: Third Trimester and Female Reproductive Organs

Third Trimester

• Full-term: 37–42 weeks; lung maturation occurs (surfactant production).

Female Reproductive Organ Differentiation

• Genetics: XX chromosomes.
• Gonadal differentiation: No SRY gene leads to ovary development.
• Phenotypic differentiation: Estrogen and progesterone shape female genitalia.

Hormone Production by Ovaries

Oogenesis vs. Spermatogenesis

Ovarian and Menstrual Cycles (~28 Days)

Ovarian Cycle Phases

1. Follicular Phase (Days 1–14):
   • Follicle grows.
2. Ovulation (Mid-cycle):
   • Release of dominant secondary oocyte.
3. Luteal Phase (Days 14–28):
   • Corpus luteum active (secretes progesterone and estrogen).

Menstrual Cycle

• Changes occur in the uterus in preparation for potential implantation.
• If no fertilization occurs, menstruation follows.