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Male Reproductive System: Accessory Gland Functions

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  • 0:05 Semen
  • 1:39 Seminal Vesicles
  • 3:45 Prostate
  • 4:29 Bulbourethral Gland
  • 5:21 Lesson Summary
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Lesson Transcript
Instructor
Heather Adewale

Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.

Expert Contributor
Ashleigh Heinz

Ashleigh earned her Master's in Physiology from NC State University and has taught college level natural sciences courses for the last 6 years

Males require a number of different glands to aid in the production of semen. Find out more about those glands in this lesson covering the male accessory glands.

Semen

Okay, class. Today's assignment is simple - all you have to do is count! Count how many sperm are in one tiny little mL of semen. Sounds simple, right? While you do that, let me first go over what exactly semen is.

I know what you're thinking - 'Aren't sperm and semen the same thing?' Well, yes and no. You see, sperm is actually part of the semen and only accounts for about 5% of the total fluid contents of semen. Sperm is produced by the testes and transported up to the male's ductus deferens, where it is stored in a region called the ampulla. It doesn't become part of semen until it is combined with fluids from the male's accessory glands.

So, semen is actually a combination of sperm and fluids secreted from the accessory gland structures found in males. This is what leaves the male's penis during the process known as ejaculation.

Wait, wait. I know your next question - 'What are accessory glands?' Right? Well, accessory glands are specialized structures found in males that produce fluids essential for the motility, nourishment and protection of sperm. These are the topics of today's lesson.

Males have three of these glands, and each one contributes to the production of semen. They are:

  1. the seminal vesicles
  2. the prostate gland
  3. the bulbourethral glands

Seminal Vesicles

The seminal vesicles produce about 60-70% of the seminal fluid
Seminal Vesicles Location

The first pair we will talk about are the seminal vesicles. These are paired secretory glands located on either side of the ampulla of the ductus deferens. They secrete about 60-70% of the seminal fluid found in semen. This fluid contains fructose for nutrition because, you know, sperm have to eat, right? It contains fibrinogen to stimulate the formation of a sperm plug or clot in the female after ejaculation. Any guesses as to the reason for this?

Well, it's kind of two-fold. First, it helps keep the sperm inside the female tract, and second is to prevent another male's sperm from fertilizing the female. Now, this may not be that useful in humans, but in the animal kingdom where many males compete over access to the same female, this sperm plug comes in quite handy.

Seminal fluid also contains prostaglandins. Prostaglandins stimulate smooth muscle contractions in both the male and female reproductive tracts. These contractions are known as peristaltic contractions and are wavelike contractions of smooth muscle.

Now, while these contractions can occur in other parts of your body - like in the esophagus as you're swallowing food - within the male reproductive tract, their purpose is to aid in the movement of sperm through the reproductive tract. Why would sperm need help, you ask? Well, they aren't really that mobile when it comes to the navigation of the reproductive tract.

You see, sperm are released from the epididymis, which completes the sperm maturation process, but this maturation process doesn't include giving sperm the mobility, or in other words the ability, to move their flagella.

So, these immobile sperm - they have to wait until they're combined with fluid from the seminal vesicles before they can start practicing their swimming. Now, even though they are somewhat mobile at this point, they can only move forward and aren't really that coordinated yet, so they still need help from the peristaltic contractions to move down the rest of the tract.

Location of the prostate gland
Prostate Gland Location

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Additional Activities

Critical Thinking Discussion Questions

Putting your critical thinking skills to the test is one of the best ways to test your knowledge and gain a deeper understanding of concepts. Try out these questions below to test your ability to extend your new knowledge to real-life scenarios. Keep in mind that you can always do additional research to help you answer these questions but you should be able to answer them through critical thinking and extension of your knowledge from the lesson.

1. Describe how the quality of the semen would be affected if the contribution by the seminal vesicles was reduced by half.

      • Hint: For this question think about the individual substances contained in the seminal vesicle fluid and what their function is. For example, what is the function of fructose and what might be the effect be of reducing the amount available?

2. The Bulbourethral glands secrete an important fluid that helps clear the male urethra of any residual urine prior to ejaculation. Why might this be important? How might urine exposure affect sperm?

      • Hint: Think about the chemical properties of urine (for example its acidic pH) and what is contained in urine (for example salts, hydrogen ions, uric acid) and how those things might impact the semen.

3. Imagine a male who is currently diagnosed with prostate cancer and how this might affect the male in a reproductive sense.

      • Hint: Take a look at the anatomy again and analyze where the prostate is located and what structures and processes could be affected by a tumor present. Also, think about the fluid produced by the prostate and how the semen might be affected if there was an over or underproduction of the prostatic fluid.

4. Sperm do not attain the ability to swim until they are mixed with the fluid from the seminal vesicles. Describe what you think would happen if sperm were able to swim without being exposed to this fluid.

      • Hint: Take a second look at the male anatomy and the location of the ampulla where sperm is stored and think what might happen if the sperm were already able to swim prior to exposure with seminal vesicle fluid.

Example Answer for #1

We learned in the lesson that the fluid from the seminal vesicles contains fructose which is used by the sperm for energy production so they can "swim" using their flagellum. Well, let's think about what might happen if we reduced the amount of available sugar by half. Now we have a reduction in the amount of sugar available which means potentially not all the sperm are able to attain enough fructose to produce adequate energy stores to swim all the way to the oocyte. If sperm are unable to reach the oocyte, there will be no fertilization so this means a change like this could definitely impact a male's fertility. We also learned about how prostaglandins are contained within this fluid and that they are responsible for producing peristaltic contractions which helps transport the sperm throughout the female reproductive tract. A reduction in seminal vesicle fluid also means a reduction in the amount of prostaglandins which could result in insufficient peristaltic contractions. Without the help of those contractions, sperm might not be able to reach the oocyte on their own without that help which will reduce the chances of an ensuing pregnancy.

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