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Although women have the chance to get
pregnant only once a month (when they ovulate), men seem
to have the ability to fertilize an egg at any time.
However, the production of sperm is not a simple one. In
fact, it takes about 74 days for sperm to be produced
and readied for ejaculation. It is important to
understand just how the male reproductive system works
in order to fully appreciate just how difficult it is
for a child to be conceived.
Testes
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).
Scrotum
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.
Epididymis
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.
Vas deferens
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
ejaculated.
Seminal vesicles
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.
Prostate gland
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.
Cowper's glands
Positioned just below the prostate, these are two small
glands that produce about 5% of the alkaline secretions
that make up semen.
Ejaculatory ducts
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.
Urethra
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.
Penis
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.
The Hormones
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).
FSH:
This
hormone is responsible for stimulating and maintaining
sperm production.
LH:
This
hormone is responsible for getting the production of
testosterone started.
Testosterone:
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.
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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. |
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