Composed of the same material that
ovaries are formed from, a man’s testicles originally
develop in his abdomen. About two months before his
birth, though, the two testes descend from the abdomen
into the scrotum, which acts as a support sac to the
testicles. The main function of testicles is two-fold:
they are responsible for producing sperm as well as the
hormone testosterone. The testicles are made up of
seminiferous tubules (hundreds of tiny tubes), Leydig
cells (which is where testosterone is produced), and
Sertoli cells (which are responsible for nurturing
immature sperm cells).
Because the testicles need to remain
about 1°C cooler than normal body temperature, the
scrotum helps to regulate the temperature of the testes.
When exposed to cold air, the scrotum contracts to keep
the testes warm but hangs lower when it is hot outside.
Found at the top of the testes, the
epididymus is a set of tightly coiled tubes. How tightly
coiled? Well, if you stretched it out, the epididymus
would reach 20 feet long. The epididymus acts as a
temporary storing place for sperm as they continue to
mature. It is within these tubes that sperm gain the
ability to move.
This long tube extends from the
epididymus in the testicle, up, over the bladder and
finally ending at the seminal vesicles. The vas deferens
acts as both a passageway for the sperm as they exit the
body and as another storing place as the sperm wait to
These two pouch-like sacs are found
behind the bladder. The seminal vesicles add an alkaline
fluid that makes up 30% of the total semen volume. This
secretion helps give the sperm energy, thereby giving
their motility a boost.
This gland sits just below the bladder
and contributes about 60% of the total semen volume.
This alkaline secretion is similar to the fluid produced
in the seminal vesicles and is necessary to the sperms’
survival by helping neutralize the naturally occurring
acids in the urethra and the vagina.
Positioned just below the prostate, these
are two small glands that produce about 5% of the
alkaline secretions that make up semen.
These are two short ducts that connect
the prostate gland to the urethra. The joining of the
two vas deferens makes up the ejaculatory ducts.
Used as the final passageway for both
semen and urine, this tube starts at the bladder, goes
through the prostate and extends to the tip of the
penis. When a man climaxes, the prostate closes off the
bladder to prevent any urine from joining the semen.
The method of delivery for sperm, this
organ is made up of veins, arteries and spongy tissue.
When a man becomes sexually aroused, the arteries dilate
allowing the tissue to become engorged with blood. This
causes the penis to stiffen and become erect.
Gonadotropin Releasing Hormone (GnRH):
Originating in the hypothalamus in the brain, GnRH is
responsible for signaling the pituitary gland to start
production of follicle stimulating hormone (FSH) and
lutenizing hormone (LH).
hormone is responsible for stimulating and maintaining
hormone is responsible for getting the production of
Produced in the Leydig cells in the testes, this hormone
helps with sperm production but it is mainly responsible
for male maturation (the deepening of the voice, sex
drive, growth and development of the sex organs).
Making It All Work
At birth, males have simple round cells contained within
their seminiferous tubules. This is the most primitive
form of sperm. During puberty, stimulation by
testosterone and other hormones cause the cells to
divide, thereby beginning the maturation process of
sperm. The sperm cells will divide and mature until they
begin to resemble tadpoles, with an oval head and long,
thin tail. Contained within the sperm head is all of the
genetic information that a man contributes to his child.
The tail is used to propel the sperm along its journey.
Once the sperm has developed its head and tail, it is
shuttled along to the epididymus. Here it will enjoy a
three-week stay by the end of which it will have gained
the ability to move. Next, the sperm move through the
vas deferens to the seminal vesicles where they stay
until they are ejaculated. All along this trip, the
sperm will be provided with fructose, a type of sugar,
to give it energy as it travels along.
During ejaculation, fluid from the prostate, seminal
vesicles, and Cowper’s gland combine with the sperm to
make semen. This will be expelled from the body during
orgasm. For fertilization of the female egg to occur, it
is necessary to ejaculate inside the vagina.
Anywhere from 250 million to 1 billion sperm are
produced and ejaculated at one time in a healthy male.
However, only about 200 of these will actually make it
up through the vagina, cervix and uterus and into the
correct fallopian tube. From this drastically reduced
group, only one sperm will actually be able to fuse
together with the egg to create a child. In total, it
takes a few days for sperm to make the trip through the
female reproductive system to the egg.