Urethra

Function

The urethra is the urinary tract's final conduit — 3–4 cm in women (opening just above the vagina), 18–20 cm in men, where it also carries semen and winds through the prostate, the pelvic floor's external sphincter and finally the corpus spongiosum.

The male urethra's three parts (prostatic, membranous, spongy) with two curves guide catheter passage; its narrowings at the meatus and membranous segment catch sounds and catheters. The female urethra's brevity is its clinical biography — an express lane for bacteria to the bladder.

Blood supply

Internal iliac (inferior vesical, internal pudendal) branches.

Nerve supply

Pudendal nerve (somatic, external sphincter); autonomic continuation of the bladder's supply.

Clinical relevance

Urethral stricture

Trauma, catheterisation or infection scars the lumen — a weakening stream that sprays; urethroplasty rebuilds it.

UTI in women

The short female urethra is a major reason UTIs are far more common in women.

Related conditions

• Urinary tract infection
• Urinary incontinence