Urethra: Anatomy and Role in the Urinary System

The urethra is a fibromuscular tube conveying urine from the bladder to the exterior—part of the lower urinary tract (with bladder).

Key Features

• Lining: Transitional epithelium (proximal) → stratified columnar → stratified squamous (distal)
• Sphincters: Internal (involuntary, smooth muscle at bladder neck); external (voluntary, skeletal muscle in urogenital diaphragm)
• Male urethra (~20 cm): Prostatic → membranous → bulbar → penile. Also conveys semen.
• Female urethra (~4 cm): Shorter, straighter; higher UTI risk

Function

Continence (sphincters + pelvic floor) and controlled voiding (detrusor contraction + sphincter relaxation coordinated by pontine micturition center).