Sperm move from the seminiferous tubules within each testis, through the rete testis and the efferent ductules, to the epididymis, and hence to the vas deferens. Passage through the epididymis contributes to sperm maturation. The columnar epithelial cells lining the epididymis absorb testicular fluid, secrete a variety of factors for sperm cell maturation and maintenance, and remove damaged sperm and residual bodies.
The epididymis is essentially a long, highly coiled tube. The epididymis is the initial portion of the duct which eventually continues as the vas deferens. This tube is surrounded by smooth muscle and embedded within a loose, vascular stroma.
- The epididymal duct is extremely long (4 to 5 meters) but is highly convoluted to fit within a small space beside the testis.
- The head of the epididymis receives the efferent ductules. Smooth muscle is quite thin around the head portion of the epididymal duct.
- The tail of the epididymis leads into the vas deferens. Smooth muscle grows progressively thicker along the epididymal duct from the head toward the tail.
- The lumen of the epididymal duct may contain clusters of spermatozoa, with small dense heads.
The epididymal duct is lined by a pseudostratified columnar epithelium, with tall columnar cells and shorter basal cells giving the appearance of two rows of nuclei. This pseudostratified epithelium lines not only the epididymis but also the vas deferens. The columnar cells are characterized by apical stereocilia (giant microvilli, not true cilia; "stereo" means "solid"). The basal cells are believed to be precursors of the columnar cells.
Note that, as an organ packed with coiled tubules, the epididymis somewhat resembles the testis. However, in the epididymis the tubules are larger, less numerous, and less closely packed; the tubule epithelium lacks germ cells; and the stroma lacks both dense fibrous connective tissue septa and conspicuous acidophilic interstitial (Leydig) cells.
SIUC / School
of Medicine / Anatomy / David
Last updated: 19 May 2022 / dgk