Prostate

Anatomically, the prostate lies inferior to the bladder neck, anterior to the rectum, and superior to the urogenital diaphragm, with the prostatic urethra running through it and the ejaculatory ducts entering from behind. Because the rectum sits directly posterior, the gland is palpable on digital rectal examination. Its blood supply comes from branches of the internal iliac artery, and venous drainage passes through the prostatic venous plexus, which communicates with the vertebral venous plexus — an anatomic route that helps explain the vertebral bone metastases seen in prostate cancer.

The gland secretes a milky, slightly alkaline fluid contributing roughly a fifth to a third of ejaculate volume. Its components include prostate-specific antigen (PSA), a protease that liquefies semen, along with citrate, zinc, and acid phosphatase. The alkalinity helps buffer the acidic vaginal environment. Development is androgen-dependent: the prostate arises from the urogenital sinus under the influence of dihydrotestosterone (DHT), which is why 5-alpha-reductase deficiency results in an underdeveloped prostate.

Two zones matter clinically. The transition zone surrounds the urethra and is where benign prostatic hyperplasia arises, compressing the urethra and producing hesitancy, weak stream, nocturia, and incomplete emptying; treatment targets smooth muscle tone with alpha-1 blockers or gland size with 5-alpha-reductase inhibitors. The peripheral zone lies posteriorly and is where most adenocarcinomas begin — which is why prostate cancer is often detectable as a hard nodule on rectal exam and why it may not cause urinary symptoms until late. Prostatitis, either acute bacterial or chronic, is the third common disorder.

USMLE Step 1 covers prostate anatomy, its embryologic origin from the urogenital sinus, and the zonal basis of BPH versus carcinoma. The NPTE for physical therapists and physical therapist assistants includes the prostate within genitourinary and reproductive system content and in oncology material, where recognition of referred pain patterns and red flags matters for screening and referral.