penile urethra

The male urethra is divided into four anatomical segments: preprostatic, prostatic, membranous, and spongy (penile) urethra. The penile urethra is the longest portion (~15 cm), running from the bulb of the penis (after the membranous urethra passes through the external urethral sphincter and perineal membrane) through the corpus spongiosum to the external urethral meatus. Along its course, it receives secretions from the bulbourethral (Cowper's) glands and numerous small mucous glands (glands of Littré), which lubricate the urethra. The epithelium is pseudostratified columnar for most of its length, transitioning to nonkeratinized stratified squamous epithelium at the fossa navicularis near the meatus, providing durability at the exit point. Clinically, the penile urethra is important in several contexts: it is the most common site of urethral strictures following trauma or infection (e.g., gonococcal urethritis, which classically causes anterior urethral strictures), hypospadias (ventral displacement of the meatus due to failure of urethral fold fusion) and epispadias, and it is the anatomical location involved in urethral catheterization complications like false passage creation. Straddle injuries can cause bulbar urethral trauma at the junction with the penile urethra. The spongy urethra's association with the corpus spongiosum protects it from compression during erection, allowing safe passage of semen. Diagnostic evaluation of the penile urethra often utilizes retrograde urethrogram (RUG) to assess for strictures, trauma, or fistulas. Understanding this anatomy is essential for urologic procedures (catheterization, cystoscopy) and evaluating congenital anomalies in pediatric practice.