Male Reproductive System Anatomy

Male Reproductive System

• The male reproductive system consists of the testes, a system of ducts, accessory sex glands, and supporting structures like the scrotum and penis.

Testes

• The testes produce sperm and secrete hormones, such as testosterone.
• Each testis is an oval organ within the scrotum.
• The testes are covered anteriorly and laterally by a serous membrane called the tunica vaginalis.
• The tunica vaginalis has an outer parietal layer and an inner visceral layer.

Scrotum

• The scrotum is a skin-covered sac that provides the testes with a cooler environment than body temperature (about 2-3°Celsius below normal body temperature).
• The scrotum is homologous to the labia majora in the female.
• The scrotum has a midline ridge called the raphe.
• The dartos muscle is a layer of smooth muscle that is part of the wall of the scrotum.

Spermatic Cord

• The spermatic cord originates in the inguinal canal and consists of:
  • Internal spermatic fascia from deep abdominal muscles.
  • Cremaster muscle and cremasteric fascia, which form from extensions of internal oblique muscles and their aponeuroses.
  • External spermatic fascia, which forms from the aponeurosis of the external oblique muscle.
  • Testicular artery, a branch of the abdominal aorta.
  • Pampiniform plexus, a network of veins surrounding the testicular artery.

Duct System

• The duct system transports and stores sperm, assists in their maturation, and conveys them to the exterior.
• The duct system consists of:
  • Rete testis
  • Efferent ductules
  • Epididymis
  • Ductus deferens (vas deferens)
  • Ejaculatory duct
  • Urethra

Epididymis

• The epididymis is situated on the posterosuperior surface of the testes.
• The epididymis stores sperm cells and assists in their maturation.
• The epididymis contains a long, convoluted duct.

Ductus Deferens

• The ductus deferens is a thick-walled duct that propels sperm through smooth muscle contractions.
• The ductus deferens travels within the spermatic cord and enters the pelvic cavity through the inguinal canal.
• The ductus deferens enlarges to form the ampulla as it approaches the prostate gland.

Ejaculatory Duct

• The ejaculatory duct is formed by the union of the ampulla of the ductus deferens and the proximal portion of the seminal vesicle.
• Each ejaculatory duct is 1-2 cm long.
• The ejaculatory duct conducts sperm and seminal vesicle secretions to the prostatic urethra.

Urethra

• The urethra transports semen from both ejaculatory ducts to the outside of the body.
• The male urethra is subdivided into three regions:
  • Prostatic urethra in the prostate gland.
  • Membranous urethra through the urogenital diaphragm.
  • Spongy urethra through the penis.

Accessory Glands

• Three glands secrete fluids to mix with sperm to create seminal fluid:
  • Seminal vesicles
  • Prostate gland
  • Bulbourethral glands

Seminal Vesicles

• The seminal vesicles are paired, elongated, hollow organs that secrete a viscous, whitish-yellow, alkaline fluid.
• The fluid contains fructose, prostaglandins, and bicarbonate, which nourish the sperm and facilitate their entry into the uterus.

Prostate Gland

• The prostate gland is located immediately inferior to the urinary bladder.
• The prostate gland secretes directly into the prostatic urethra.
• The prostatic secretion is slightly acidic and contains mucin, citric acid, seminalplasmin, and prostatic-specific antigen (PSA).

Bulbourethral Glands

• The bulbourethral glands are paired, pea-shaped glands that sit in the urogenital diaphragm on either side of the membranous urethra.
• The glands secrete clear, viscous mucin that lubricates the urethra prior to ejaculation.

Semen

• Seminal fluid from the three accessory glands combines with sperm from the testes to make up semen.
• When released during intercourse, semen is called ejaculate.
• Ejaculate normally measures about 3-5 ml in volume and contains 200-500 million sperm.

Penis

• The penis and scrotum form the external genitalia in males.
• The penis consists of:
  • The root, forming the bulb and crura of the penis.
  • The body (shaft), an elongated portion.
  • The glans, which surrounds the external urethral orifice.
  • The prepuce, the foreskin of an uncircumcised penis.
• The shaft of the penis contains three parallel, cylindrical erectile bodies:
  • Paired corpora cavernosa, located dorsolaterally.
  • A single corpus spongiosum, ventral and along the midline, surrounding the spongy urethra.

Erection and Ejaculation

• Erection occurs when the erectile bodies fill with blood, aided by parasympathetic innervation.
• Ejaculation is the expelling of semen from the penis, aided by rhythmic contraction of smooth muscle in the urethra and sympathetic innervation.