Vas deferens


Vas deferens
Vas deferens
Male anatomy en.svg
Male Anatomy
Gray1149.png
Vertical section of the testis, to show the arrangement of the ducts.
Artery Superior vesical artery, Artery of the ductus deferens
Lymph external iliac lymph nodes, internal iliac lymph nodes
Precursor Wolffian duct
MeSH Vas+Deferens

The vas deferens (plural: vasa deferentia), also called ductus deferens, (Latin: "carrying-away vessel"; plural: ductus deferentes), is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation.

Contents

Structure

There are two ducts, connecting the left and right epididymis to the ejaculatory ducts in order to move sperm. Each tube is about 30 centimeters long (in humans) and is muscular (surrounded by smooth muscle).

They are part of the spermatic cords.

Function in ejaculation

During ejaculation the smooth muscle in the walls of the vas deferens contracts reflexively, thus propelling the sperm forward. This is also known as peristalsis. The sperm is transferred from the vas deferens into the urethra, collecting secretions from the male accessory sex glands such as the seminal vesicles, prostate gland and the bulbourethral glands, which form the bulk of semen.

Significance in contraception

The procedure of deferentectomy, also known as a vasectomy, is a method of contraception in which the vasa deferentia are permanently cut, though in some cases it can be reversed. A modern variation, which is also known as a vasectomy even though it does not include cutting the vas, involves injecting an obstructive material into the ductus to block the flow of sperm.

Investigational attempts for male contraception have focused on the vas with the use of the intra vas device and reversible inhibition of sperm under guidance

Blood supply

The vas deferens is supplied by an accompanying artery (artery of vas deferens). This artery normally arises from the superior vesical artery, a branch of the internal iliac artery.

Variation among vertebrates

Most vertebrates have some form of duct to transfer the sperm from the testes to the urethra. In cartilaginous fish and amphibians, sperm is carried through the archinephric duct, which also partially helps to transport urine from the kidneys. In teleosts, there is a distinct sperm duct, separate from the ureters, and often called the vas deferens, although probably not truly homologous with that in humans.[1]

In cartilaginous fishes, the part of the archinephric duct closest to the testis is coiled up to form an epididymis. Below this are a number of small glands secreting components of the seminal fluid. The final portion of the duct also receives ducts from the kidneys in most species.[1]

In amniotes, however, the archinephric duct has become a true vas deferens, and is used only for conducting sperm, never urine. As in cartilaginous fish, the upper part of the duct forms the epididymis. In many species, the vas deferens ends in a small sac for storing sperm.[1]

The only vertebrates to lack any structure resembling a vas deferens are the primitive jawless fishes, which release sperm directly into the body cavity, and then into the surrounding water through a simple opening in the body wall.[1]

Pathology

The vas deferens may be obstructed, or may be completely absent (the latter a potential feature of cystic fibrosis), causing male infertility. It can be overcome by testicular sperm extraction (TESE), collecting sperm cells directly from the testicles.

Additional images

See also

References

  1. ^ a b c d Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 393–395. ISBN 0-03-910284-X. 

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Vas deferens — Vas Vas, n.; pl. {Vasa}. [L., a vessel. See {Vase}.] (Anat.) A vessel; a duct. [1913 Webster] {Vas deferens}; pl. {Vasa deferentia}. [L. vas vessel + deferens carrying down.] (Anat.) The excretory duct of a testicle; a spermatic duct. [1913… …   The Collaborative International Dictionary of English

  • vas deferens — [vas def′ə renz΄] n. pl. vasa deferentia [vā′sə def΄ə ren′shē ə] [ModL < L vas, vessel + deferens, carrying down: see DEFERENCE] the highly convoluted duct that conveys sperm from the testicle to the ejaculatory duct of the penis …   English World dictionary

  • vas deferens — ► NOUN (pl. vasa deferentia) Anatomy ▪ the duct which conveys sperm from the testicle to the urethra. ORIGIN from VAS(Cf. ↑V) + Latin deferens carrying away …   English terms dictionary

  • vas deferens — /vas def euh renz , euhr euhnz/, pl. vasa deferentia /vay seuh def euh ren shee euh, sheuh/. Anat., Zool. the duct that transports the sperm from the epididymis to the penis. [1880 85; < NL vas deferens lit., vessel for carrying off. See VAS,… …   Universalium

  • vas deferens — vas de•fe•rens [[t]ˈvæs ˈdɛf əˌrɛnz, ər ənz[/t]] n. pl. va•sa de•fe•ren•ti•a [[t]ˈveɪ sə ˌdɛf əˈrɛn ʃi ə, ʃə[/t]] anat. zool. a duct that transports sperm from the epididymis to the penis • Etymology: 1880–85; < NL vās dēferēns lit., vessel… …   From formal English to slang

  • Vas deferens — Vas deferens,   der Samenleiter …   Universal-Lexikon

  • vas deferens — Duct in male passage of sperm from testis to penis [McLaughlin, 1980]. Ducts in males for passage of spermatozoa from testis to penis [Moore and McCormick, 1969]. Male duct from the testis to the penile papilla for the passage of sperm [Wilson,… …   Crustacea glossary

  • vas deferens — vas def·er·ens def ə rənz, .renz n, pl vasa def·er·en·tia .def ə ren ch(ē )ə a sperm carrying duct esp. of a higher vertebrate that in humans is a small but thick walled tube about two feet (0.6 meter) long formed by the union of the vasa… …   Medical dictionary

  • Vas deferens — Der Samenleiter (lat. Ductus deferens, Vas efferens) verbindet bei männlichen Säugetieren, Vögeln und Reptilien den Nebenhoden mit der Harnröhre und dient der Weiterleitung der Spermien. Der Samenleiter durchzieht, vom Nebenhoden kommend,… …   Deutsch Wikipedia

  • vas deferens — [ dɛfərɛnz] noun (plural vasa deferentia ˌdɛfə rɛnʃɪə) Anatomy the duct which conveys sperm from the testicle to the urethra. Origin C16: from vas + L. deferens carrying away , pres. participle of deferre …   English new terms dictionary


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.