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Reproductive System
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.
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
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