Surgical anatomy of the male and female urethra.

The urethra is lined by transitional and stratified columnar epithelium. The urethra can be divided into both anatomic (prostatic, membranous, bulbar, and pendulous) and functional (anterior and posterior) segments. In the male, the anterior urethra is contained within the corpus spongiosum and penis. The urethra in the male and female is located within the urogenital triangle and pierces the superficial and deep perineal spaces of the pelvic floor. The urethra is surrounded by perineal and pelvic musculature that provide support and also form the urethral sphincter mechanism. Cancers of the anterior urethra preferentially drain into superficial inguinal lymph node channels. Those of the posterior urethra (prostatic, membranous, and bulbar segments in the male and the proximal two thirds of the urethra in the female) generally drain into pelvic lymphatic channels. A thorough knowledge of urethral and regional anatomy allows for complete tumor excision, optimal reconstruction, and in selected cases, restoration of urinary tract function.