All Access Pass - 1 FREE Month!
Institutional email required, no credit card necessary.

Male Reproductive Tract (Anatomy)

Overview
  • The reproductive system facilitates sexual maturation of individuals and sexual reproduction of offspring.
  • In the male, this includes the production of semen and its delivery to the outside environment.
  • Specific anatomical adaptations, such as the penis, facilitate semen delivery close to the site of conception, within the female reproductive tract.
  • Semen comprises sperm cells and seminal plasma, which nourishes and protects the sperm.
  • Reproductive structures are classified as either primary or accessory (aka, secondary):
    • The primary structures are referred to as gonads; their function is to produce gametes, aka, sex cells. In males, the primary structures are the testes (aka, testicles), which produce sperm and hormones.
    • The accessory structures are the organs, ducts, and glands that facilitate delivery of the gametes to the external environment.
Ejaculation
  • Emission is when semen is ushered into proximal urethra.
  • Expulsion is when semen is projected through urethra.
Testes
Epididymis
  • Wraps over posterior-superior aspect of testis.
  • Long coiled tube that stores developing sperm.
Ductus deferens
  • Continuous with epididymis, ascends to enter the pelvis, then passes over the urinary bladder and ureter.
  • It is a muscular tube that actively conducts sperm from the epididymis to the ejaculatory duct; this transport occurs during the emission phase of ejaculation.
  • Ampulla is the widened end of the ductus deferens.
Seminal vesicle
  • Is adjacent to the ampulla.
  • Contributes the majority of the total seminal plasma volume.
Ejaculatory duct
  • Drains the ductus deferens and the seminal vesicle into the prostatic urethra.
Prostate gland
  • Its secretions enter the prostatic urethra.
Bulbourethral glands (aka, Cowper's glands)
  • Lie lateral to the prostate and secrete lubricating mucus into the spongy urethra.
  • During the expulsion phase of ejaculation, secretions from the bulbourethral glands precede the rest of the seminal fluid.
Key Function:
Conduct urine and semen to the outside environment.
2ND CARD:
Key Anatomical Features of the Penis:
Skin
  • Prepuce covers glans, is retractable in the adult.
Vessels
  • Superficial dorsal vein and artery
  • Deep dorsal vein
  • Deep arteries within corpus cavernosa
Connective tissues
  • Deep fascia surrounds erectile bodies and binds them together
  • Intercavernous fascia separate corpora cavernosa from corpus spongiosum.
  • Covered in tunica albuginea
  • Comprise vascular tissues that engorge with blood upon arousal.
Singular corpus spongiosum surrounds the urethra:
  • Glans is distal expansion; corona is rim of glans
  • Bulb is the widened proximal end
  • The bulb anchors the corpus spongiosum to the perineal membrane (not shown);
  • The bulb is wrapped in the bulbospongiosum muscle, which contracts to: force blood into the erectile tissues, eject residual urine from the urethra,
and produce pulsatile movements during ejaculation.
Paired corpus cavernosa (singular = cavernosum)
  • Lie dorsal to corpus spongiosum
  • Crus (singular = crura) of the corpus cavernosa extend laterally
  • Crus attach to the pubic arch of the pelvis (not visible here), and are wrapped by ischiocavernosus muscles; like the bulbospongiosum, these muscles force blood into the erectile tissues.
Root
  • Comprises bulb and crus of penis
Shaft
  • Free, pendulous portion of penis between root and glans
Urethra
  • Conducts semen to external environment
  • Terminates at external urethral orifice
  • Urethral glands secrete mucus to protect urethra from urine
Anatomical orientation
  • Dorsal surface faces the torso
  • Ventral surface faces away from the torso.
Clinical correlations:
  • Vasectomy: the paired ductus deferens are surgically sealed shut; sperm is still produced, but cannot be transported to the ejaculatory ducts to join the seminal plasma.
    • Thus, it is a highly effective form of contraception that is sometimes surgically reversed.
  • Cryptorchidism, aka, undescended testis, is a common birth abnormality in boys; the testicles usually move into the scrotum on their own, but, if not, surgery may be necessary.
    • Complications of cryptorchidism include increased likelihood of testicular cancer and reduced fertility.