REPRODUCTIVE SYSTEM (MALE & FEMALE)

• Gonads — primary sex organs

  • Testes in males
  • Ovaries in females
• Gonads produce gametes (sex cells) and secrete hormones

  • Sperm — male gametes
  • Ova (eggs) — female gametes
• ANATOMY OF THE MALE REPRODUCTIVE SYSTEM

  Testes

  • Duct system

  - Epididymis

  - Ductus (vas) deferens

  - Urethra
• ANATOMY OF THE MALE REPRODUCTIVE SYSTEM

  Testes

  Accessory organs

  - Seminal glands (vesicles) - Prostate - Bulbourethral glands
• ANATOMY OF THE MALE REPRODUCTIVE SYSTEM

  Testes

  External genitalia

  • Penis
  • Scrotum
• Each testis is connected to the trunk via the spermatic cord, which houses:

  • Blood vessels
  • Nerves
  • Ductus deferens
• Coverings of the testes

  Tunica albuginea — capsule that surrounds each testis Septa — extensions of the capsule that extend into the testis and divide it into lobules
• Each lobule contains one to four seminiferous tubules

  • Tightly coiled structures
  • Function as sperm - forming factories
  • Empty sperm into the rete testis
• Sperm travels from the rete testis to the epididymis
• Interstitial cells in the seminiferous tubules produce androgens such as testosterone
• The duct system transports sperm from the body and includes:

  • Epididymis
  • Ductus deferens
  • Urethra
• Epididymis

  • Highly convoluted tube 6 m (20 ft) long
  • Found along the posterior lateral side of the testis
  • First part of the male duct system
  • Temporary storage site for immature sperm
  • Sperm mature as they journey through the epididymis
  • During ejaculation, sperm are propelled to the ductus deferens
• Vas Deferens

  • Runs from the epididymis via the spermatic cord through the inguinal canal and arches over the urinary bladder
  • Moves sperm by peristalsis into the urethra
• Ampulla — end of the ductus deferens, which empties into the ejaculatory duct
• Ejaculatory duct — passes through the prostate to merge with the urethra
• Ejaculation — smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze sperm forward
• Vasectomy — cutting of the ductus deferens at the level of the testes prevents transportation of sperm (form of birth control)
• Urethra

  • Extends from the base of the urinary bladder to the tip of the penis
  • Carries both urine and sperm
  • Sperm enters from the ejaculatory duct
• Urethra regions

  Prostatic urethra — surrounded by prostate gland

  Membranous urethra — prostatic urethra to penis

  Spongy (penile) urethra — runs the length of the penis to the external urethral orifice
• Ejaculation causes the internal urethra sphincter to close

  • Prevents urine from passing into the urethra
  • Prevents sperm from entering the urinary bladder
• Accessory Organs and Semen

  • Seminal Glands (Vesicles)
  • Located at the base of the bladder Produce a thick, yellowish secretion (60% of semen) that contains:
  • Fructose (sugar)
  • Vitamin C
  • Prostaglandins
  • Other substances that nourish and activate sperm
  • Duct of each seminal vesicle joins that of the ductus deferens on each side to form the ejaculatory duct
• Prostate

  • Encircles the upper (prostatic) part of the urethra
  • Secretes a milky fluid
  • Helps to activate sperm
  • Fluid enters the urethra through several small ducts
• Bulbourethral Gland

  • Pea-sized glands inferior to the prostate
  • Produce a thick, clear mucus - Mucus cleanses the spongy (penile) urethra of acidic urine prior to ejaculation - Mucus serves as a lubricant during sexual intercourse
• Semen

  • Milky white mixture of sperm and accessory gland secretions
  • Components of accessory gland secretions
  • Liquid portion acts as a transport medium to dilute sperm
  • Sperm are streamlined cellular “tadpoles”
  • Fructose provides energy for sperm cells
  • Alkalinity of semen helps neutralize the acidic
  • environment of vagina
  • Semen inhibits bacteria
• External Genitalia

  Scrotum

  • Divided sac of skin outside the abdomen that houses the testes
  • Viable sperm cannot be produced at normal body temperature
  • Maintains testes at 3°C lower than normal body temperature
• External Genitalia

  Penis


  Male organ of copulation that delivers sperm into the female reproductive tract
• Regions of the penis

  • Shaft
  • Glans penis (enlarged tip)
  • Prepuce (foreskin)
• Prepuce (foreskin)

  - Folded cuff of skin around proximal end - Often removed by circumcision
• Internally there are three areas of spongy erectile tissue around the urethra
• Erections occur when this erectile tissue fills with blood during sexual excitement
• MALE REPRODUCTIVE FUNCTIONS


  Chief roles of the male in the reproductive process

  - Produce sperm - Produce a hormone, testosterone
• Spermatogenesis

  Sperm production

  - Begins at puberty and continues throughout life - Millions of sperm are made every day
• Sperm are formed in the seminiferous tubules of the testis

  • Spermatogonia (primitive stem cells) begin the process by dividing rapidly
  • During puberty, follicle-stimulating hormone (FSH) is secreted in increasing amounts
• Each division of a spermatogonium stem cell produces:

  • Type A daughter cell, a stem cell, that continues the stem cell population
  • Type B daughter cell, which becomes a primary spermatocyte, destined to undergo meiosis and form four sperm
• Meiosis

  • Special type of nuclear division that differs from mitosis
  • Occurs in the gonads
  • Includes two successive divisions of the nucleus (meiosis I and II)
  • Results in four daughter cells (gametes)
• Gametes are spermatids with 23 chromosomes

  23 chromosomes are half the usual 46 found in other body cells

  23 is known as the haploid number (n)—half the genetic material as other body cells
• Union of a sperm (23 chromosomes, n) with an egg (23 chromosomes, n) creates a zygote (2n, or 46 chromosomes)
• Spermiogenesis

  • Spermatids are nonmotile and not functional as sperm
  • A streamlining process is needed to strip excess cytoplasm from a spermatid and modify it into a sperm
  • A sperm has three regions: head, midpiece, tail
  • Acrosome sits anterior to the sperm head (nucleus)
  • The entire process of spermatogenesis, including spermiogenesis, takes 64 to 72 days
• Testosterone Production

  During puberty:

  • Follicle-stimulating hormone (FSH) begins prodding seminiferous tubules to produce sperm
  • Luteinizing hormone (LH) begins activating the interstitial cells to produce testosterone
• Testosterone

  • Most important hormonal product of the testes
  • Stimulates reproductive organ development
  • Underlies sex drive
  • Causes secondary sex characteristics