The male urethra is a narrow fibromuscular tube that conducts urine and semen from the bladder and ejaculatory ducts, respectively, to the exterior of the body (see the image below). Although the male urethra is a single structure, it is composed of a heterogeneous series of segments: prostatic, membranous, and spongy.
Male urethra and its segments.
Most proximally, the prostatic urethra is responsible for involuntary continence, transmission of semen into the common genitourinary tract, and the most common site of bladder outlet obstruction in the Western world. The membranous urethra is critical to voluntary continence and, because of its rigid attachments, is highly susceptible to injury in pelvic trauma. The spongy urethra is surrounded by the corpus spongiosum and forms the terminal conduit communicating with the outside of the body.
Knowledge of male urethral anatomy is essential for all health professionals because urethral catheterization is one of the most commonly performed procedures in health care. The male urethra is susceptible to a variety of pathologic conditions, ranging from traumatic to infectious to neoplastic. Pathophysiologic variants of the urethra may have devastating consequences, such as renal failure and infertility.