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 somniferous tubules
(hundreds of tiny tubes), Leyden cells (which is where
testosterone is produced), and Sterol 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.
Epidermis
Found at the top of the testes, the epidermis is a set of
tightly coiled tubes. How tightly coiled? Well, if you stretched
it out, the epidermis would reach 20 feet long. The epidermis
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 epidermis 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
Gonadotroptin 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 luteinizing
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
epidermis. 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.
