bulbourethral gland

**Anatomy** - Paired, pea-sized (~1 cm) exocrine glands located in the deep perineal pouch, posterolateral to the membranous urethra and embedded in the external urethral sphincter (sphincter urethrae). - Each gland has a duct (~2.5 cm) that passes through the perineal membrane and empties into the proximal bulb of the spongy (penile) urethra. - Blood supply: branches of the internal pudendal artery (artery of the bulb of the penis). Innervation: sympathetic (via hypogastric/pelvic plexus) stimulates emission; parasympathetic input contributes to pre-ejaculatory secretion. - Lymphatics: internal iliac nodes.

**Embryology** - Arise from endoderm of the urogenital sinus (urethral epithelium) under the influence of dihydrotestosterone (DHT) via 5-alpha-reductase type 2. - Homologous to the greater vestibular (Bartholin) glands in females (which lie in the superficial perineal pouch and open at the vaginal vestibule). Mnemonic: Cowper (male) = Bartholin (female). - Contrast: seminal vesicles, vas deferens, epididymis derive from the mesonephric (Wolffian) duct; prostate derives from the urogenital sinus endoderm.

**Histology/Physiology** - Compound tubuloalveolar glands lined by mucus-secreting cuboidal/columnar cells. - Secretion (pre-ejaculate): clear, viscous, alkaline mucus/galactose-rich glycoprotein fluid that (1) lubricates the urethra, (2) neutralizes acidic residual urine and the acidic vaginal environment (protective for sperm), and (3) flushes out urethral debris. Contains few or no sperm normally (though sperm may be present from prior ejaculation). - Semen contribution order (approx.): seminal vesicles ~60–70% (fructose, prostaglandins, fibrinogen/semenogelin), prostate ~20–30% (citrate, PSA, acid phosphatase, zinc), bulbourethral ~5%, testes/epididymis ~5% (sperm). - Sequence of ejaculation: Emission (sympathetic, T10–L2) → Ejaculation (somatic, pudendal nerve S2–S4, bulbospongiosus contraction). Erection is parasympathetic (S2–S4, pelvic splanchnic nerves, NO-mediated), "point" (pudendal nerve).

**Clinical Significance** - Cowperitis (bulbourethral gland inflammation): usually from ascending urethral infection, e.g., Neisseria gonorrhoeae or Chlamydia; presents with perineal pain/fullness, dysuria, and purulent discharge. Abscess is rare. - Cowper duct syringocele (cystic dilation of the duct): can cause obstructive voiding symptoms, post-void dribbling, hematuria, or recurrent UTI in children; diagnosed by voiding cystourethrogram, treated by endoscopic marsupialization. - Injury: straddle injuries or urethral injury at the bulbar/membranous urethra region may involve the glands. Remember that the urogenital diaphragm/perineal membrane lies between the membranous and bulbar urethra: rupture of the **bulbar (spongy) urethra** (straddle injury) causes urine extravasation into the superficial perineal pouch (butterfly-pattern bruising of perineum, scrotum, penis, limited by Colles fascia and Scarpa fascia, not into the thigh because of fascial attachments to fascia lata), while rupture of the **membranous urethra** (pelvic fracture) causes extravasation into the deep perineal pouch/retropelvic space with a high-riding prostate. - Cancer: primary carcinoma of the bulbourethral gland is extremely rare. - Pre-ejaculate may contain sperm and pathogens (e.g., HIV), which explains the failure rate of the withdrawal (coitus interruptus) method of contraception. - Vasectomy does not affect bulbourethral secretions or ejaculate appearance because the accessory glands remain intact; only sperm (~5% of volume) is lost. - Androgen dependence: glands atrophy with androgen deficiency; 5-alpha-reductase deficiency impairs development of external genitalia and prostate, but Wolffian derivatives (epididymis, vas, seminal vesicles) develop normally because they depend on testosterone, not DHT.

**High-yield pearls** - Location: deep perineal pouch (male); Bartholin glands: superficial perineal pouch (female). - Duct opens into the bulbar (proximal spongy) urethra. - Produces alkaline mucus pre-ejaculate (neutralizes acidic urethra). - Homologue: Bartholin gland.