Overview
The male urethra is a 20 cm fibromuscular tube connecting the urinary bladder with the external urethral meatus. It contains small blinding ending pockets (lacunae) and numerous mucous urethral glands (of Littre). It is the terminal portion of the genitourinary tract, transporting urine and semen.
Course
Prostatic urethra
- Continuation of the bladder neck, passing through the prostate gland
- Wide, most dilatable
- Receives:
- Ejaculatory ducts – contains spermatozoa from testes, seminal fluids from seminal vesicle glands
- Prostatic ducts – contains alkaline fluid
Membranous urethra
- Continuation of the prostatic urethra, passing through the pelvic floor and deep perineal pouch
- Narrow, least dilatable
- Surrounded by the external urethral sphincter
- Voluntary control of micturition
- Tonically contracted via somatic fibers that originate in Onuf’s nucleus and pass through sacral spinal nerves S2-S4 then the pudendal nerve to synapse on the muscle
Bulbous (penile or spongy) urethra
- Continuation of the membranous urethra, passing through the bulb and corpus spongiosum of the penis, ending at the external urethral orifice
- Receives:
- Bulbourethral glands (Cowper’s glands) proximally and posterolaterally – pea-shaped excocrine gland contributing to the volume of semen by producing a lubricating mucous secretion
- Largest part (15cm) within the corpus spongiosum (erectile tissue) of the penis
- In the glans of the penis, dilates to form the navicular fossa
Blood supply
- Prostatic urethra – supplied by the inferior vesical artery (branch of the internal iliac artery which also supplies the lower part of the bladder)
- Membranous urethra – supplied by the bulbourethral artery (branch of the internal pudendal artery, branch of the internal iliac artery)
- Bulbous/penile/spongy urethra – supplied directly by branches of the internal pudendal artery
Veins
- Dorsal veins of the penis and internal pudendal veins, drain into prostatic and vesical venous plexuses and into internal iliac veins
Lymphatics
- Anterior urethra drains into deep and superficial inguinal nodes
- Posterior urethra drains into obturator and internal iliac nodes
Nerves
- Perineal branches of pudendal nerve (S2-4) supplies external sphincter
- Inferior hypogastric plexus
Variants
- Epispadias – defect of the dorsal wall of the urethra
- Hypospadias – urethra opens on the underside of penis
- Anterior and posterior urethral valves
- Duplication
- Congenital stricture