Epididymis
Epididymis
A comma-shaped structure on the posterior border of the testis, formed by a single tightly coiled duct about 6 m long, in which sperm mature, gain motility and are stored.
Overview
The epididymis has a head (caput) at the upper pole formed by the coiled efferent ductules, a body (corpus) along the posterolateral border, and a tail (cauda) at the lower pole that turns sharply upward as the ductus deferens. The duct of the epididymis is about 4–6 m long, compressed into ≈5 cm by tight coiling.
Its lining is pseudostratified columnar epithelium with long, non-motile microvilli called stereocilia (absorptive) and basal stem cells, surrounded by a thin layer of smooth muscle that thickens towards the tail. The epididymis reabsorbs much of the testicular fluid (concentrating sperm), secretes glycoproteins, carnitine and sialic acid that modify the sperm surface, and phagocytoses degenerating sperm.
During transit (≈10–14 days), sperm acquire progressive forward motility and the ability to recognise and bind the zona pellucida. The tail stores sperm for weeks; smooth muscle contraction during emission propels them into the ductus deferens.
- Location
Posterolateral surface of the testis, inside the tunica vaginalis except for its posterior border; the sinus of the epididymis (a recess of tunica vaginalis) separates its body from the testis.
Parts & subdivisions
- Head (caput)Efferent ductules converging into the epididymal duct; contains the appendix of the epididymis (a Wolffian remnant).
- Body (corpus)Coiled duct along the posterolateral testis.
- Main storage site; continuous with the ductus deferens.
Anatomy
- Innervation
Sympathetic fibres from the testicular and pelvic plexuses (contraction at emission).
- Arterial supply
Branches of the testicular artery; the tail also from the artery to the ductus deferens.
- Venous drainage
Pampiniform plexus.
- Lymphatic drainage
With the testicular lymphatics to para-aortic (lumbar) nodes.
- Histology
Pseudostratified columnar epithelium with stereocilia (principal cells) and basal cells; smooth muscle coat thickening from head to tail; lumen packed with sperm.
- Development
Mesonephric (Wolffian) duct, retained under the influence of testosterone; efferent ductules from mesonephric tubules.
Function
- Maturation of sperm (motility, zona-binding capacity).
- Concentration of sperm by fluid reabsorption.
- Storage of sperm (tail).
- Propulsion of sperm during emission (smooth muscle).
Clinical significance
Epididymitis
Painful swelling of the epididymis, often with urethritis; Chlamydia trachomatis and N. gonorrhoeae in sexually active younger men, enteric organisms (E. coli) in older men or after instrumentation. Elevation may relieve pain (Prehn sign — unreliable for excluding torsion).
Epididymal cyst and spermatocele
Smooth, transilluminating swellings separate from and usually above the testis.
Compiled from standard anatomy and physiology references — see the Reproductive System sources. For education only; not medical advice.