ejaculatory duct

**Anatomy** - Formed by the union of the ampulla of the vas deferens (carries sperm from epididymis) and the duct of the seminal vesicle (secretes ~60-70% of semen volume: fructose, prostaglandins, fibrinogen/semenogelin). - Length ~2 cm; paired. Travels obliquely through the central zone of the prostate, then opens into the prostatic urethra on either side of the prostatic utricle at the seminal colliculus (verumontanum). - Blood supply: inferior vesical artery and artery to the vas (branch of the superior/inferior vesical artery). - Embryology: derived from the mesonephric (Wolffian) duct. The prostatic utricle is a remnant of the paramesonephric (Müllerian) ducts (homologue of the uterus/vagina). The seminal vesicle arises as an outgrowth of the mesonephric duct. Wolffian duct development depends on testosterone from Leydig cells. - Prostate zones: ejaculatory ducts run through the central zone (~25% of prostate; resistant to cancer and BPH, associated with inflammation).

**Physiology** - Sympathetic control (T10-L2 via hypogastric nerve) causes emission: smooth muscle contraction of the vas, seminal vesicles, and prostate moves fluid into the prostatic urethra. - Somatic control (pudendal nerve, S2-S4) causes expulsion: rhythmic contraction of bulbospongiosus and ischiocavernosus muscles. Mnemonic: "Point (parasympathetic) and Shoot (sympathetic)"; erection = parasympathetic (S2-S4 pelvic splanchnic nerves, NO/cGMP), emission = sympathetic, ejaculation = visceral and somatic (pudendal) nerves. - Bladder neck (internal urethral sphincter) closes during emission (sympathetic α1) to prevent retrograde ejaculation.

**Clinical significance** - Ejaculatory duct obstruction (EDO): cause of low-volume, acidic (seminal vesicle fluid is alkaline, so absence lowers pH), fructose-negative azoospermia or oligospermia. Causes: congenital (Müllerian duct/utricle cysts, Wolffian duct cysts), acquired (prostatitis, instrumentation/TURP, stones, trauma). Dx: transrectal ultrasound (dilated seminal vesicles >1.5 cm AP diameter, dilated ducts, cysts). Tx: transurethral resection of ejaculatory ducts (TURED). - Congenital bilateral absence of the vas deferens (CBAVD): associated with CFTR mutations (cystic fibrosis); also yields low-volume, acidic, fructose-negative azoospermia with normal spermatogenesis and normal FSH/testosterone. - Obstructive azoospermia: normal FSH, normal testis size, normal spermatogenesis on biopsy (versus nonobstructive: high FSH, small testes). - Retrograde ejaculation: damage to sympathetic innervation or bladder neck (diabetic neuropathy, retroperitoneal lymph node dissection, TURP, α-blockers such as tamsulosin); causes post-orgasm cloudy urine with sperm. - Hematospermia: can result from inflammation or obstruction of the ejaculatory ducts or seminal vesicles; usually benign. - Prostatitis can lead to ejaculatory duct reflux and inflammation. - Surgical relevance: vasectomy interrupts the vas deferens proximal to the ejaculatory duct; ejaculate volume remains largely unchanged since sperm contribute <5% of volume.

**High-yield pearls** - Vas deferens + seminal vesicle duct = ejaculatory duct → prostatic urethra. - Seminal vesicle: fructose (energy source for sperm), alkaline fluid; absence of fructose points to EDO or CBAVD. - Ejaculatory ducts open at the verumontanum; the prostatic utricle (Müllerian remnant) lies between the openings. - Wolffian derivatives (SEED): Seminal vesicles, Epididymis, Ejaculatory duct, Ductus (vas) deferens.