Seminal Vesicles and Bulbourethral Glands as Male Accessory Sex Organs

What are the Male Accessory Sex Organs?

Semen produced by males require the active functions of the male accessory sex organs to become properly formed. In fact, without these accessory organs, sperms present within the semen may become unable to fertilize an ova or egg within the fallopian tube (or oviduct) of the female reproductive system.

To better comprehend the distinctions between semen and sperm, Please read on the male reproductive system (scrotum and its contents) here.

The accessory male reproductive organs include the followings:

1. Seminal Vesicles
2. Prostate Gland

   Please read on the Male Accessory Sex Organs (Prostate Glands) and Ejaculatory Ducts here.

3. Bulbourethral Glands or Cowper's Glands

The focus of this article will be on the seminal vesicles and and Bulbourethral Glands as male accessory sex organs:

• Seminal Vesicles

A male has a pair of seminal vesicles (vesicula seminalis) located just above the prostrate gland; and posterior to the base of the urinary bladder.

Below is an image showing the anatomical position of the seminal vesicle:

The main function of the seminal vesicle is to add viscous and alkaline secretions to the sperm already present in the ejaculatory ducts.

The secretions or fluid of the seminal vesicle does the following:

• The alkalinity of this fluid helps to neutralize any acidity produced in the environment of the urethra. (The acidity of the urethral environment may result from the passage of acidic urine through it).
  You can read on the Concepts and Definitions of Acid here.
• The secretions of the seminal vesicles also neutralizes the acidic environment of the vagina, hence fostering sperm survival within it.

The seminal fluid is composed up of the followings:

1. Fructose

This is a simple sugar that's used for ATP (Adenosine Tri Phosphate) generation.

ATP is the energy essential for sperm motility. This is important because the sperms may swim upwards (against gravity) in the female reproductive tract.

For now, think of ATP as the energy currency of the body.

Please read on Carbohydrates and Sugars here.

2. Prostaglandins

They reduce the negative effects of the female immune system that may act upon the sperm cells. This process increasing the chances of a sperm's survival in the female reproductive tract.

Please read on Immunization here.

3. Semenogelin

This fluid creates a gel like structure around the sperm, thus protecting it. The appearance of semen is largely attributed to the viscosity of the semenogelin.

• Bulbourethral Glands

They are also called the Cowper’s gland.

The bulbourethral glands are two pea like shaped organs located just below the prostate gland and at the beginning (or root) of the penis.

Please read on Male Reproductive System (Penis and Parts of the Penis) here.

The anatomical position of the bulbourethral glands are shown in the diagram below:

In addition to the prostate and seminal fluids, the bulbourethral glands also secrete fluid into the semen during the process of ejaculation. The fluid from the bulbourethral glands serve the following functions:

• The fluid is clear and thick, functioning to lubricate the urethra. The semen flows out of the penis through the lubricated urethra.
• It is also considered that the bulbourethral secretions creates a better condition for sperm cells to survive.

Note: Although the urethra isn't considered a part of the male accessory reproductive gland, it still performs a vital role in the male reproductive system.

You can read on the Introduction to Human Brain here.

Below is a summarized explanation on the urethra:

• Urethra

The male urethra is a single tube-like structure that serves two functions. These are:

1. Micturition. (The act of urinating).
2. Conduction and Movement of semen during ejaculation.

In males, the urethra is a narrow fibro-muscular tube that conducts urine from the bladder to the exterior. It also conducts semen from the ejaculatory ducts to the exterior.

The conduction on urine and semen through the urethra does not occur simultaneously.

The male urethra is about 7 to 8 inches in length; and it runs through the prostate gland, seminal vesicles and the entire length of the penis before emptying its content to the exterior.

The urethra has three sections. These are:

1. Prostatic Urethra: This is the uppermost portion of the urethra. It lies inside the prostate gland.

3. Membranous Urethra: This is the segment within the urethral sphincter. It is important to state that urine or semen can only come out singly (one at a time); and that's when the membranous urethra is opened.

3. Spongy or Penile Urethra: This is the lowest and longest section of the urethra. It lies within the entire length of the penis, leading to the exterior. (Please see the image above)

Note: The exterior opening of the urethra is also called the external urethral orifice or meatus.