Ductus Deferens Definition - The vas deferens is also called the ductus deferens, a tube-like muscular structure found in the sperm cord that forms a major part of the male reproductive system. This creates a continuous epididymis that participates in the transport of sperm from the epididymis to the ejaculatory ducts.
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The male vas deferens is a 45cm long structure found at the back of the bone and close to the epididymis in the sperm cord. It incorporates a seminal vesicle pathway to form the ejaculatory duct.
Ductus Deferens Anatomy
The ductus vas deferens are about 45 inches long and begin to convoluted but straighten as they ascend from the course posterior to the testis and medial to the epididymis. When it reaches the upper part of the testicles, it moves superiorly in the posterior aspect of the spermatic cord. The ductus deferens then crosses the inguinal canal before it emerges from the sperm canal into the deep inguinal ring and It also surrounds the lower epigastric artery and extends anteriorly to the external iliac artery. The vas (ductus) deferens then crosses the outer iliac vessels in an oblique and slightly posterior direction.
Following this, ductus defence enters the lesser pelvis, where it is retroperitoneal, and transverse medially and posteriorly to the vesicle vessels. The vas (ductus) deferens then crosses over the ureter at a posterolateral angle of the bladder. As soon as it crosses the ureter, the vas (ductus) deferens expands and is called the ampulla of the vas (ductus) deferens. It then passes between the upper part of the seminal vesicle and the posterior surface of the bladder in an anteromedial direction.
The vas (ductus) deferens then moves downward along the base of the bladder, anterior to the rectum, before it joins the seminal vesicle duct, at an acute angle, to form the ejaculatory duct.
The Function of Vas Deferens
The primary function of vas deferens (ductus deferens) is to transport spermatozoa from the epididymis to the ejaculatory ducts. The sympathetic nervous system during ejaculation encapsulates the muscle layers of the ductus deferens causing them to produce strong peristaltic contractions to aid in the propulsion of spermatozoa. As a result, the vas deferens transfers sperm to the urethra which helps to prepare for ejaculation. Sperm is transferred from the vas deferens to the urethra mixing partially with the secretion from the male accessory gland (bladder glands, abdominal tissues and bulbourethral glands).
Parts of Ductus Deferens
The structure of tissue of ductus deferens consists of epithelial tissue, a middle layer of connective tissue and visceral muscle and finally an outer layer of adventitia.
Epithelial tissue is pseudostratified columnar that makes up the inner lining of the vas deferens and it contains many absorptive stereocilia. The function of the vas deferens of this layer is to absorb excess liquid and also dead sperm while secreting nutrients to support sperm during their storage and transportation.
The thickest layer of the ductus deferens of is the middle layer, which contains many elastin fibres and visceral muscle cells arranged in longitudinal and circular bundles.
Visceral muscle will push the sperm along the length of the ductus deferens due to the action of contraction, while elastin fibres allow the wall of the tubule to expand and contract along with the muscle cells.
In the last, the outer adventitia of ductus deferens consists of areolar connective tissue, which helps to surround the tissue, so that it remains stationary throughout the person’s life and through the countless waves of the peristalsis.
Do You Know?
That the ductus deferens serves a dual function in the male reproductive system: one is the transportation of sperm from the testes to the ejaculatory duct and urethra, and the other is to store sperm until it is ready for ejaculation.
The sperm that passes through the ductus deferens is not matured enough to be able to swim or move (motile) and thus it has to be transported through peristalsis movement. The smooth muscle tissue in the walls of the ductus deferens contracts in a way to create peristalsis movement to slowly move the sperm along its length. Once the sperm has reached its end of the ductus deferens, it will be stored in the widened ampulla for several months, until the ejaculation occurs. When the sperms left vas deferens become old and damaged they will be absorbed by the epithelial lining of the ampulla and it is broken by the body and their parts reused in other cells.