Spongy Urethra

Structure/Morphology

In a flaccid penis, the spongy urethra is approximately 15 cm long and extends from the membranous urethra to the external urethral orifice (Standring, 2016). The proximal part of the spongy urethra is termed the bulbar urethra. This because the bulbourethral glands open into the urethra here. The distal part of the spongy urethra curves downwards and is termed the penile urethra. The penile urethra dilates at its terminal portion within the glans penis as the navicular fossa.

Anatomical Relations

The spongy urethra lies within the corpus spongiosum of the penis.

Function

The spongy urethra provides passage for urine and semen out of the body by way of the male external urethral orifice.

Arterial Supply

The urethral artery, a branch of the internal pudendal artery, enters the penis, just inferior to the perineal membrane. It supplies the spongy urethra and surrounding erectile tissue. Circumflex branches of the dorsal artery of the penis also supply the spongy urethra.

Venous Drainage

The venous drainage of the spongy urethral is mainly through dorsal veins of the penis and internal pudendal veins, which drain into the prostatic plexus.

Innervation

Autonomic fibers arrive at the spongy urethra by way of the prostatic plexus, an inferior extension of the inferior hypogastric plexus. Lumbar splanchnic nerves supply sympathetic innervation, whereas the pelvic splanchnic nerves supply parasympathetic innervation to the spongy urethra. Somatic innervation is supplied by dorsal nerve of the penis, a branch of the pudendal nerve.

Lymphatic Drainage

Lymphatic drainage of the spongy urethra drains mainly into the deep inguinal and external iliac lymph nodes.

List of Clinical Correlates

—Kidney stones

—Hypospadias

—Urethritis

—Catheterization

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.