Male urethra

Anatomical divisions:

• posterior urethra
  • prostatic urethra:
    • 3-4 cm in length
    • verumontanum is a prominence on the posterior wall; ejaculatory ducts open on either side
  • membranous urethra:
  • 2 cm in length
    • from apex of the prostate to the bulb of the penis
    • site of sphincteric activity
• anterior urethra:
  • includes bulbar and penile urethra
  • surrounded by corpus spongiosum
  • involved in emptying of urine at end of voiding and emission of semen during ejaculation
  • corpora cavernosa lie dorsally

Blood supply:

• branches from internal pudendal artery; run through the corpus cavernosum in the 5 'o' clock and 7 'o' clock positions
• branches of dorsal arteries to the penis; run proximally from glans penis into corpus cavernosum

Determinants of sphincteric activity:

• inner layer of smooth muscle
• outer layer of striated muscle, innervated by S2 and S3

Histology:

• transitional cell epithelium proximally
• squamous cell epithelium near external meatus at fossa navicularis