Quick Facts
Location: Pelvis and perineum.
Arterial Supply: Urethral artery.
Venous Drainage: Internal pudendal vein.
Innervation: Sympathetic: lumbar splanchnic nerves, vaginal nerve and uterovaginal plexus (females), prostatic plexus (males); Parasympathetic: pelvic splanchnic nerves, lumbosacral nerves, vaginal nerve, and uterovaginal plexus (females); Somatic: pudendal nerve.
Lymphatic Drainage: External and internal iliac lymph nodes.
Related parts of the anatomy
Structure/Morphology
The urethral wall consists of three layers, including a mucosal, muscular, and erectile layer. The proximal epithelium is transitional epithelium, while the distal epithelium is stratified squamous.
The male urethra is approximately 20 cm long and divided into four segments (intramural, prostatic, membranous, and spongy). The female urethra is approximately 4 cm long and is not subdivided into multiple portions.
Anatomical Relations
The urethra connects the bladder to the urinary meatus. In males the urethra runs through the penis, in females the urethra emerges anterior to the vaginal opening.
Function
Provides passage for urine (and semen in males only).
Arterial Supply
In males, the urethral artery passes medially to travel through the corpus spongiosum to reach the glans penis. It travels through the perineal membrane and corpus spongiosum to reach the glans penis.
As the urethra is much shorter in females, the urethral artery is much small in caliber and is not always present. In these cases, the urethra in is supplied by the vaginal and inferior vesical arteries.
Venous Drainage
Venous plexuses around the urethra drains into the vesical venous plexus around the bladder, which drains into the internal pudendal veins.
Innervation
The urethra receives both autonomic and somatic innervation. Somatic innervation is primarily received through the perineal branch of the pudendal nerve. Autonomic fibers travel through the inferior hypogastric, uterovaginal (females) or prostatic (males) plexuses in order to reach the urethra. Splanchnic innervation is primarily from lumbar splanchnic nerves, whereas parasympathetic innervation is received via pelvic splanchnic nerves and caudal lumbosacral nerves. In addition, the urethra sends somatic information via the perineal branch of the pudendal nerve (Standring, 2016).
Lymphatic Drainage
Lymphatic drainage of the urethra mainly passes to the internal and external iliac lymph nodes. Some, however, may pass to the deep and superficial inguinal lymph nodes (Földi et al., 2012).
List of Clinical Correlates
—Kidney stones
—Hypospadias
—Urethritis
—Catheterization
References
Földi, M., Földi, E., Strößenreuther, R. and Kubik, S. (2012) Földi's Textbook of Lymphology: for Physicians and Lymphedema Therapists. Elsevier Health Sciences.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.
