Vasa Deferentia: Definition, Structure & Function

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

The male reproductive system is riddled with scary sounding vocabulary. We will unpack this information so you can understand the male reproductive system, specifically the vasa deferentia.

The Male Reproductive System

When we think of human reproduction, the focus is often on the mother and all the processes her body goes through. But, as they say, it takes two to tango! The male reproductive system, or the internal and external structures responsible for creating new life, contains a plethora of fascinating details you may have never known. For example:

  • The male reproductive system produces the smallest human cell: the sperm.
  • A man produces over 500 billion sperm cells in his lifetime.
  • The testicles are made up of a bunch of tubes, and if they were unraveled, they would be about 3 feet long.
  • In an effort to outdo the testes, if you were to uncoil the tubes making up the epididymis, they would reach 20 feet.
  • There is a muscle that lowers and raises the testicles in order to keep them at a specific temperature
  • A vasectomy is a permanent method of birth control where the vasa deferentia is severed.

But what do all of those words mean? Vasectomy? Epididymis? Vasa deferentia? Don't worry, keep reading!

Vasa Deferentia Defined

Let's focus on a piece of the male reproductive system just mentioned: the vas deferens (singular) or the vasa deferentia (plural). Most male vertebrates (animals with backbones) have vasa deferentia.

In humans, each male has two vas deferens, which are tubes that transport sperm from the epididymis to the urethra in preparation for ejaculation. Whoa, that was a bit of vocabulary. Let's unpack it.

Following the Sperm

In order to understand the function of the vasa deferentia, let's follow the path of sperm during ejaculation. Sperm is produced in the testes (singular: testicle or testis) and from there it travels to the epididymis, which is a series of tiny tubes that carry the sperm to the vas deferens.

If you were to uncoil the tubes, they would reach 20 feet (remember that fun fact!). The entire structure of the epididymis is crescent-shaped and sperm mature as they travel through them. Before we go on, let me give you some tricks to remember some of this vocabulary.

  • 'Vas deferens' translates into 'carrying away vessel' in Latin. That makes sense since it is carrying sperm away from the testicles.
  • Epididymis means 'upon or over the testicle' in Greek. If you see it's location, that's a pretty accurate name.

Location of epididymis
epidg

Okay, back to following the sperm. When a male is sexually stimulated, blood fills the penis, which causes it to become erect. The mature sperm leaves each epididymis, and travels through the vasa deferentia to a structure called the ampulla, which is just a portion of the vas deferens that is enlarged.

Ampulla and other structures
amupd3

In the ampulla, other fluids are added to the sperm. Next, the sperm and these other fluids are pushed past the prostate, which is a gland found in males that adds a milky fluid to the sperm. This fluid protects and aids the sperm once it reaches the vagina.

Semen is the term coined to describe sperm plus all of these extra fluids. Lastly, the semen is expelled from the body through the urethra. The urethra is the opening in the penis where urine (and, as just mentioned, semen) exit the body.

Structure and Function of the Vasa Deferentia

Now that you know the basic function of the vasa deferentia, let's take a moment to examine how its structure is related to its function. There are two vas deferens and each one is connected to an epididymis. Remember, males have two testicles, so two epididymides.

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