urethra

The urethra is a tubular conduit that carries urine from the urinary bladder to the exterior of the body. In males it also serves as a passage for semen during ejaculation. The urethra’s length and course differ between the sexes, reflecting its dual roles in humans.

In males, the urethra is typically about 18 to 22 cm long and is divided into four contiguous segments: the intramural (preprostatic) portion within the bladder neck, the prostatic urethra passing through the prostate, the membranous urethra traversing the pelvic floor, and the penile (spongy) urethra running through the corpus spongiosum to the external meatus at the glans penis. The male urethra is closely integrated with the reproductive tract and receives various ducts along its course.

In females, the urethra is much shorter, about 3 to 4 cm, and courses from the internal urethral orifice at the bladder neck to the external meatus located between the clitoris and the vaginal opening. The female urethra lies anterior to the vaginal canal and does not convey semen.

Histology varies along the length of the urethra. The proximal portions are lined by urothelium (transitional epithelium), with distal segments showing pseudostratified or stratified squamous epithelium near the external meatus.

Common clinical considerations include urethral infection (urethritis), urethral strictures, hypospadias in males, urethral trauma, and urinary incontinence related to urethral sphincter function. Catheterization and endoscopic procedures are common procedures involving the urethra.