Male Reproductive Organs and Functions

The anatomy and the location of the male reproductive system.

The male reproductive system includes the following structures:

• Penis
• Scrotum
• Testes (testicles)
• Vas deferens
• Seminal vesicles
• Prostate gland
• Urethra

What Is the Penis?

The penis consists of three main parts, the root, the body, and the glans penis.

The root is attached to the abdominal and pelvic walls.

The body is the middle portion. The body of the penis consists of three cylindrical spaces of soft tissue. When the two larger spaces fill with blood, the penis becomes large and rigid, forming an erection. Two larger cylindrical spaces of soft tissue called the corpora cavernosa are located side by side and form the bulk of the penis. The third cylindrical space of soft tissue, called the corpus spongiosum, surrounds the urethra, which forms the urinary passage.

The glans penis is the cone-shaped end or head of the penis, which is the termination of the corpus spongiosum. The small ridge that separates the glans penis from the shaft or body of the penis is called the corona.

The testes (or testicles) are two olive-sized oval bodies, one on the right side and one on the left side. The testes have two main functions,

• to produce sperm (the male reproductive cell), and
• to produce testosterone (the male sex hormone).

The epididymides and the vasa deferentia are attached to the testicles and are important in transporting sperm cells after they develop in the testes.

The term testicles include the testes as well as the surrounding structures, such as the vas deferens and the epididymis. These two names, testes, and testicles, are often used interchangeably even though their definitions are slightly different.

The scrotum is a thin sac of skin and thin muscle in which lie the testicles. The scrotum acts as a climate control system, allowing the testicles to be slightly away from the rest of the body and keeping them slightly cooler than normal body temperature for optimal sperm development.

• The muscles in the scrotum called the cremasteric muscles, move the testicles slightly within the scrotum depending on the surrounding temperature.

Once sperm are produced, they travel through a collection area, called the epididymis, and then through a tube or duct, called the vas deferens, which then joins the seminal vesicles to form the ejaculatory duct. The seminal vesicles produce a fluid that provides nutrients for the sperm and lubricates the urethra. This fluid mixes with other fluids to create semen.

During ejaculation, muscles surrounding the seminal vesicles contract and push out the sperm and the fluid from the seminal vesicles, much like squeezing a tube of toothpaste. The seminal vesicles are located behind the prostate and the bladder.

Illustration of the prostate gland.

The prostate is a walnut-sized gland that lies below the urinary bladder and surrounds the urethra. Along with the seminal vesicles, the prostate gland produces a fluid, called prostatic fluid, that contains, protects, nourishes, and supports the sperm. The white, sticky fluid originally from the prostate forms most of the volume of the semen. The prostate has no known function other than reproduction.

The prostate grows throughout life. This growth often causes a blockage in the urethra that affects voiding with such symptoms as

• urinary frequency,
• excessive urination at night (nocturia),
• the urgency of urination, and
• weakening of the urinary stream.
• This enlargement of the prostate, called benign prostatic hyperplasia (or BPH), can be treated with medication or various surgical procedures.

The prostate is also the source of a prostate-specific antigen (or PSA) that is used as a blood test to detect and monitor prostate cancer.

The urethra is surrounded by the corpus spongiosum, one of the cylindrical spaces of the soft tissue of the penis described earlier. In men, the urethra provides a dual purpose,

• to transport urine from the bladder, and
• to transport the semen (sperm cells and fluid from the seminal vesicles and the prostate) out of the tip of the penis.

Scar tissue in this passage, called strictures, can cause urinary difficulty.