More About Ductus Deferens
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.
FAQs on Ductus Deferens
1. What is the ductus deferens?
The ductus deferens, also commonly known as the vas deferens, is a long, muscular tube found in the male reproductive system. Its main role is to act as a pathway, connecting the epididymis (where sperm are stored and mature) to the ejaculatory ducts in preparation for ejaculation.
2. What is the main function of the ductus deferens in the male reproductive system?
The primary function of the ductus deferens is to transport mature sperm from the epididymis towards the urethra. During ejaculation, the thick muscular walls of the ductus deferens contract powerfully in a wave-like motion, a process called peristalsis, to propel the sperm forward.
3. Are 'ductus deferens' and 'vas deferens' the same thing?
Yes, 'ductus deferens' and 'vas deferens' refer to the exact same anatomical structure. 'Ductus deferens' is the more modern and formal term used in anatomy, while 'vas deferens' is the older and more widely recognised name for the sperm-carrying tube.
4. Where exactly is the ductus deferens located in the body?
The ductus deferens starts at the lower part (tail) of the epididymis, which is attached to the back of each testis. From there, it travels upwards within the spermatic cord, passes into the pelvic cavity, and loops behind the bladder. Its journey ends where it joins the duct of the seminal vesicle to form the ejaculatory duct.
5. What kind of tissues make up the wall of the ductus deferens?
The wall of the ductus deferens is thick and strong, which is essential for its function. It is made of three distinct layers:
- An inner mucosal lining.
- A very thick middle layer of smooth muscle, which provides the force for ejaculation.
- An outer layer of fibrous connective tissue that provides support.
6. What happens to sperm if the ductus deferens is blocked or cut, like in a vasectomy?
If the ductus deferens is blocked or surgically cut during a vasectomy, it physically stops sperm from travelling from the epididymis to mix with semen. The testes continue to produce sperm, but since they have nowhere to go, they are simply and safely reabsorbed by the body. This is why a vasectomy is an effective method of birth control.
7. How is the ductus deferens different from the ejaculatory duct?
The main difference is their specific job and structure. The ductus deferens is a long tube whose only job is to transport sperm. The ejaculatory duct is a much shorter tube formed when the ductus deferens merges with the duct from the seminal vesicle. Its job is to mix the sperm with seminal fluid and then empty the resulting semen into the urethra.
8. What path does sperm take after leaving the ductus deferens?
At the end of its path, the ductus deferens widens to form an area called the ampulla. Here, it joins with the duct from a gland called the seminal vesicle. This union forms the short ejaculatory duct. From there, the mixture of sperm and fluid (semen) is propelled into the urethra to exit the body during ejaculation.
