The epididymis (plural: epididymides) is situated adjacent to the testes within the scrotal sac. Its primary function is the collection, maturation and transport of sperm via the ductus deferens.

The epididymis is an elongated structure, posterolateral to testes, with head, body and tail regions. 

The total length of the epididymis is usually 6-7 cm in length but it is tightly coiled and would measure 6 m if uncoiled 3.

The head is its largest and most recognisable part and is found at the superior pole of the testis. The head of the epididymis measures approximately 5-12 mm in length and may have a small projection called the appendix of the epididymis 3. The tail of the epididymis is found at the inferior pole of the testis 3.

Seminiferous tubules carry the sperm via tubuli recti into a dilated space within mediastinum testes which is known as rete testes. Rete testes drains into epididymis through 10-15 efferent ductules 1. Efferent ducts in the head of epididymis (globus major) unite to form a single duct  in the body and tail region (globus minor), which continues as the ductus deferens.

Deferential artery (a branch of superior vesical artery) and testicular artery (a branch off the aorta) supply the inferior and superior portions of the epididymis, respectively.

Some sources state that the epididymis is supplied only by branches of the testicular artery 5.

See article: Testicular and scrotal ultrasound

Normal epididymis is iso-to-hyperechoic to the testes, with equal or less vascularity on colour and spectral Doppler. The head of the epididymis is visualized superior and lateral to the testes, while the body and the tail are smaller with variable locations 2.

  • T1: epididymis has homogenously intermediate signal
  • T2: epididymis has hyperintense signal, with slightly lower signal than testes.

"Epididymis" derives from the Greek έπιδιδνμίς (έπί "upon" + δίδνμος "testicle"). Δίδνμοι (meaning "twins") was an older term for both testicles and ovaries. Galen originally used the term to refer to what we now call the tunica, and used the term "parastates" ("standing beside") for what we call the epididymis. Herophilus may have been the first to use it in the current sense.

Abdominal and pelvic anatomy
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Article information

rID: 17879
System: Urogenital
Section: Anatomy
Synonyms or Alternate Spellings:
  • Epididymides

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