Composed of the same material that ovaries are formed
from, a manís 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 1įC 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 be
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 spermsí
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 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
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 Cowperís 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.