The epididymis is part of the human male reproductive system and is present in all male mammals. It is a
narrow, tightly-coiled tube connecting the efferent ducts
from the rear of each testicle to its vas deferens.
Regions
The epididymis can be divided into three main regions
- the head (caput)
- the body (corpus)
- the tail (cauda)
Role in storage of sperm and ejaculation
Spermatozoa formed in the testis enter the caput epididymis, progress to the corpus, and
finally reach the cauda region, where they are stored. Sperm entering the caput epididymis are incomplete - they lack the ability
to swim forward (motility) and to fertilize an egg.
During their transit in the epididymis, sperm undergo maturation processes necessary for them to acquire these functions.[1] Final maturation is completed in the female reproductive tract (capacitation).
During ejaculation, sperm flow from the lower portion of the epididymis (which functions
as a storage reservoir). They are packed so tightly that they are unable to swim, but are transported via the peristaltic action of muscle layers within the vas deferens, and are mixed with the diluting fluids of the seminal
vesicles and other accessory glands prior to ejaculation (forming semen).
The epididymis is one of only two regions of the body to have stereocilia
(the inner ear being the other.)[2]
Pathology
An inflammation of the epididymis is called epididymitis. It is a swollen blood vessel
from the testicle that appears or feels like an enlarged epididymis.
Embryology and vestigial structures
A Gartner's duct is a homologous remnant
in the female.
Embryologically, the epididymis is derived from tissue that once formed the
mesonephros, a primitive kidney found in many aquatic
vertebrates. Persistence of the cranial end of the mesonephric duct will leave behind a remnant called the appendix of the epididymis. Additionally, some mesonephric tubules can persist as the
paradidymis, a small body caudal to the efferent ductules.
Additional images
Male reproductive system.
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Schematic drawing of a cross-section through the vaginal process.
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References
- Moore, Keith L. & Persaud, T.V.N. (2003). The Developing Human: Clinically Oriented Embryology (7th ed.).
Philadelphia: Saunders. ISBN 0-7216-9412-8
External links
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Male reproductive system |
| Scrotum |
layers (skin, Dartos,
External spermatic fascia, Cremaster, Internal spermatic fascia) •
Perineal raphe • Spermatic cord |
| Testes |
layers (Tunica vaginalis, Tunica albuginea) •
Appendix • Mediastinum •
Lobules • Septa • Leydig cell • Sertoli cell • Blood-testis barrier |
| Spermatogenesis |
Spermatogonium •
Spermatocytogenesis • Spermatocyte •
Spermatidogenesis • Spermatid •
Spermiogenesis • Spermatozoon |
| seminal tract |
Seminiferous tubules (Tubuli seminiferi recti,
Rete testis, Efferent ducts) • Epididymis (Appendix) • Vas deferens • Ejaculatory duct
Seminal colliculus |
| urinary tract |
Internal urethral
orifice • Urethra (Prostatic,
Intermediate, Spongy) • Urethral crest • Urethral gland • External urethral orifice |
| Penis |
Corpus cavernosum • Corpus
spongiosum • Navicular fossa of male urethra •
Glans penis • Fundiform
ligament • Suspensory ligament • Foreskin • Frenulum |
| accessory glands |
Seminal vesicles (Excretory duct of seminal
gland) • Prostate (Prostatic
utricle, Prostatic sinus) • Bulbourethral glands |
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