seminal vesicles

Embryologically derived from the mesonephric (Wolffian) duct, seminal vesicles develop alongside the vas deferens, epididymis, and ejaculatory ducts—explaining why congenital anomalies here often co-occur with renal agenesis (since the ureteric bud also arises from the mesonephric duct). Histologically, they are lined by pseudostratified columnar epithelium with a highly folded mucosa. Their secretions are alkaline, helping neutralize vaginal acidity, and contain fructose to nourish sperm, prostaglandins to stimulate smooth muscle contractility (aiding sperm transport), and semenogelin, which coagulates semen after ejaculation (later liquefied by PSA from the prostate). Clinically, seminal vesicle invasion by prostate cancer upstages disease to at least T3b, indicating locally advanced disease and worse prognosis—assessed via digital rectal exam, transrectal ultrasound, or MRI. Congenital absence of the vas deferens (as seen in cystic fibrosis) is often associated with seminal vesicle agenesis or hypoplasia, contributing to obstructive azoospermia and infertility. Seminal vesicle cysts can be associated with ipsilateral renal agenesis (Zinner syndrome). On semen analysis, absence of fructose suggests seminal vesicle dysfunction or obstruction of the ejaculatory ducts.