Epididymis
The epididymis is a tightly coiled tube on the back of each testis. Sperm pass into it from the testis, mature as they move along it and are stored in its tail. (OpenStax A&P 2e, 27.1; StatPearls, Abdomen and Pelvis: Testes)
Open it in the Male Reproductive Organs Explorer See it alone in 3D
Where is the epididymis?
It lies along the posterior border of the testis. Its head sits at the upper pole of the testis and receives fluid from the ducts of the testis. (StatPearls, Abdomen and Pelvis: Testes)
On the back and outer side of the testis, a small gap between the testis and the body of the epididymis is called the sinus of the epididymis. (StatPearls, Abdomen and Pelvis: Testes)
What are the parts of the epididymis?
It has three parts: a head, a body and a tail. Straightened out, its duct would be about 6 m, or 20 feet, long. (StatPearls, Abdomen and Pelvis: Testes; OpenStax A&P 2e, 27.1)
It develops from the mesonephric, or Wolffian, duct of the embryo. In males that duct also forms the deferent duct, the seminal vesicles and the ejaculatory ducts. (StatPearls, Abdomen and Pelvis: Kidneys)
What does the epididymis do?
Sperm arrive unable to swim. Over about 12 days in its long, coiled duct they mature and gain the ability to move, then wait in its tail until ejaculation. (OpenStax A&P 2e, 27.1; StatPearls, Abdomen and Pelvis: Testes and Physiology, Male Reproductive System; Holstein et al. 2003, Reprod Biol Endocrinol)
At ejaculation, smooth muscle contraction drives sperm out of the tail into the deferent duct. (OpenStax A&P 2e, 27.1; StatPearls, Physiology, Male Reproductive System)
What lies next to the epididymis?
It sits inside the scrotum with the testis and the spermatic cord. The tunica vaginalis wraps the testis except along its back and upper borders, where the epididymis and the spermatic cord attach, and its inner, visceral layer lies close against the epididymis, the testis and the deferent duct. (StatPearls, Abdomen and Pelvis, Scrotum and Abdomen and Pelvis: Testes)
Its tail leads into the deferent duct, which runs up inside the spermatic cord and through the inguinal canal into the abdomen. (OpenStax A&P 2e, 27.1; StatPearls, Physiology, Male Reproductive System)
How does the epididymis vary?
In about 7% of males the epididymis lies on the front of the testis. A small appendix of the epididymis, a remnant of the mesonephric duct, is present in about 25% of testes, often at the head. (StatPearls, Abdomen and Pelvis: Testes)
| Feature | Detail and source |
|---|---|
| Parts | Head, body, tail (StatPearls, Abdomen and Pelvis: Testes) |
| Uncoiled length | About 6 m (20 feet) (OpenStax A&P 2e, 27.1; StatPearls, Abdomen and Pelvis: Testes) |
| Sperm transit | About 12 days (OpenStax A&P 2e, 27.1; StatPearls, Physiology, Male Reproductive System; Holstein et al. 2003, Reprod Biol Endocrinol) |
| Leads to | Deferent duct (OpenStax A&P 2e, 27.1; Gray 1918, 3c. The Male Genital Organs; StatPearls, Physiology, Male Reproductive System) |
Touches in this model
Measured on the BodyParts3D meshes: surfaces within 2 mm of the epididymis, nearest first.
- Left deferent duct in contact
- Left testis in contact
- Right deferent duct in contact
- Right testis in contact
Sources
- OpenStax Anatomy and Physiology 2e, section 27.1, Anatomy and Physiology of the Testicular Reproductive System. CC BY-NC-SA 4.0. Read 2026-10-25.
- StatPearls, Anatomy, Abdomen and Pelvis: Testes. Manpreet S. Tiwana; Stephen W. Leslie. Last update April 15, 2023. CC BY-NC-ND 4.0. Read 2026-10-25.
- StatPearls, Anatomy, Abdomen and Pelvis: Kidneys. Felix A. Garza; Stephen W. Leslie. Last update September 15, 2025. CC BY-NC-ND 4.0. Read 2026-10-25.
- StatPearls, Physiology, Male Reproductive System. Purnima Gurung; Ekrem Yetiskul; Ishwarlal Jialal. Last update May 1, 2023. CC BY-NC-ND 4.0. Read 2026-10-25.
- Reproductive Biology and Endocrinology, Understanding spermatogenesis is a prerequisite for treatment, Reprod Biol Endocrinol 1, article 107 (full text, PMC293421; PMID 14617369). Holstein AF, Schulze W, Davidoff M. BioMed Central open access; verbatim copying and redistribution permitted with the notice. Read 2026-10-25.
- StatPearls, Anatomy, Abdomen and Pelvis, Scrotum. Rosa A. Garcia; Hussain Sajjad. Last update July 24, 2023. CC BY-NC-ND 4.0. Read 2026-10-25.
- Gray’s Anatomy of the Human Body, 20th US edition (1918), XI. Splanchnology, 3c. The Male Genital Organs, 1. The Testes and their Coverings (1918 terms: tubuli seminiferi, tubuli recti and ductuli efferentes for seminiferous tubules, straight tubules and efferent ductules). Henry Gray. Public domain. Read 2026-10-25.
The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.