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Epididymis
Illu testis surface.jpg
1: Epididymis
2: Head of epididymis
3: Lobules of epididymis
4: Body of epididymis
5: Tail of epididymis
6: Duct of epididymis
7: Deferent duct (ductus deferens or vas deferens)
Gray1148.png
The right testis, exposed by laying open the tunica vaginalis.
Gray's subject #258 1242
Vein Pampiniform plexus
Precursor Wolffian duct
MeSH Epididymis

The epididymis (pronounced /ɛpɨˈdɪdɨmɪs/, plural: epididymides /ɛpɨˌdɪdɨˈmiːdiːz/) is part of the male reproductive system and is present in all male amniotes. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. A similar, but probably non-homologous, structure is found in cartilaginous fishes.

Contents

Regions

The epididymis can be divided into three main regions

  • The head (Caput). The head of the epididymis receives spermatozoa via the efferent ducts of the mediastinum of the testis. It is characterized histologically by a thin myoepithelium. The concentration of the sperm here is dilute.
  • The body (Corpus)
  • The tail (Cauda). This has a thicker myoepithelium than the head region, as it is involved in absorbing fluid to make the sperm more concentrated.

In reptiles, there is an additional canal between the testis and the head of the epididymis, which receives the various efferent ducts. This is, however, absent in all birds and mammals.[1]

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.[2] 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 have not been activated by products from the prostate gland, and 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 possesses numerous, long atypical microvilli. These processes are often called stereocillia; this is incorrect, as they neither contain the microtubular structures of cilia nor function like cilia.[3]

Pathology

An inflammation of the epididymis is called epididymitis.

Embryology and vestigial structures

A Gartner's duct is a homologous remnant in the female.

In the embryo, the epididymis develops 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. In addition, some mesonephric tubules can persist as the paradidymis, a small body caudal to the efferent ductules.

Epididymectomy

This is the surgical removal of the Epididymis carried out under local anaesthesia. This is most often performed to relieve pain associated post-Vasectomy.

Gallery

Notes

  1. ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 394-395. ISBN 0-03-910284-X.  
  2. ^ Jones R (1999). "To store or mature spermatozoa? The primary role of the epididymis". Int J Androl 22 (2): 57–67. doi:10.1046/j.1365-2605.1999.00151.x. PMID 10194636.   abstract
  3. ^ Stevens, Alan; Lowe, James N. (2005). Human histology. Philadelphia: Elsevier Mosby. ISBN 978-0-323-03663-4.  

External links


Simple English

Epididymis
1: Epididymis
2: Head of epididymis
3: Lobules of epididymis
4: Body of epididymis
5: Tail of epididymis
6: Duct of epididymis
7: Deferent duct (ductus deferens or vas deferens)
Gray's subject #258 1242
Vein Pampiniform plexus
Precursor Wolffian duct
MeSH Epididymis

The epididymis is the part of the human male reproductive system. It is the tube that holds the testicles in place. It stretches from the back of each testicle to the van deferens.

Contents

Parts

The dinges is made up of three parts:

  • The head (Caput)
  • The body (Corpus)
  • The tail (Cauda)

Uses

Sperm made in the testis go into the head (caput) of the epididymis, go through the body (corpus) and stop at the tail (cauda), where they are stored. When sperm are first made and travel to the head, they are not yet ready to be ejaculated. They cannot swim or fertilize an egg. By the time they reach the tail, the sperm can fertilize an egg. The sperm are transferred to the Seminal visicle through the vas deferens. The sperm can not swim yet, so muscle contractions push the sperm to the seminal vesicle where final development is finished. .[1]

When the sperm are ejaculated, they move through the tail of the epididymis. There are so many sperm that they cannot swim, but use peristalsis from muscles in the vas deferens.

Disease

An injury or infection of the epididymis causes epididymitis, a painful condition that can take months to heal. Sometimes the testicle has to be removed. There does not seem to be any single cause, or treatment for this condition. Some doctors treat it with antibiotics, some take a "wait and see" attitude. At times just one testicle is affected and at others, both.

Pictures

References








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