prostatic urethra

The prostatic urethra is the widest and most dilatable portion of the male urethra, extending from the internal urethral orifice (bladder neck) through the prostate gland to the urogenital diaphragm, where it becomes the membranous urethra. Key anatomical landmarks include: the urethral crest, a longitudinal ridge on the posterior wall; the seminal colliculus (verumontanum), an elevation on the crest where the prostatic utricle (a vestigial remnant of the paramesonephric duct) opens along with the two ejaculatory ducts (carrying sperm from the vas deferens and seminal vesicles); and the prostatic sinuses on either side of the crest, into which numerous prostatic ducts drain secretions containing PSA, zinc, and citrate. The prostatic urethra is lined by transitional epithelium proximally and stratified/pseudostratified columnar epithelium distally. Clinically, this region is central to benign prostatic hyperplasia (BPH), where hyperplasia of the periurethral (transition) zone compresses the prostatic urethra causing bladder outlet obstruction, presenting with urinary hesitancy, weak stream, nocturia, and incomplete emptying. Prostate cancer typically arises in the peripheral zone and is often asymptomatic until advanced, unlike BPH. Transurethral resection of the prostate (TURP) is performed through this segment to relieve obstruction, and retrograde ejaculation is a known complication due to disruption of the internal urethral sphincter/bladder neck function. The prostatic urethra also serves as an important landmark in Foley catheter placement and cystoscopy. Autonomic innervation (sympathetic fibers via hypogastric nerve) mediates smooth muscle tone at the bladder neck and prostate, relevant to alpha-1 blocker (e.g., tamsulosin) therapy in BPH.