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Male reproductive system
Male reproductive system Sperm are formed in the two testes.
These hang below the penis because human body temperature is
too high for proper sperm formation. The sperm are stored in
the epididymis, just above the testes. During sex, the sperm
move through tubes and are mixed with secretions from the
prostate gland and Cowper's gland, both ducted glands. The
result is called semen. Semen exits the body through a tube
in the penis called the urethra.
Female reproductive system Corresponding to the testes in
males, the ovaries produce eggs (also known as ova). Unlike
sperm, eggs can be stored at human body temperature, so the
ovaries are located inside the pelvis. Eggs pass through the
Fallopian tubes to the uterus or womb, which is partly sealed
at the other end by the cervix. The fetus develops in the
uterus. On the other side of the cervix is a muscular tube
called the vagina. The vagina is the main part of the birth
canal, so named because the offspring passes through the canal
to be born.
Role The purpose of the reproductive system is to produce
offspring. The process begins when the precursor to an egg
cell, or ovum, goes through a complex maturation process that
eventually makes it the largest cell in the human body, just
barely observable to the naked eye. The reason for this great
size is that the mature ovum is filled with the nutrient
substance called yolk. When this process, which takes about
ten days, is complete, the ovum is released from the ovary,
an event called ovulation (OV-yoo-LAY-shun). The ovum moves
into the nearby Fallopian tube, where it may encounter sperm
cells if copulation has taken place. A fertilized cell moves
to the uterus.
Conditions that affect the reproductive system In some ways
the reproductive system is fragile - often it seems as if any
disease, from AIDS to yellow fever, interferes with
reproduction. Some diseases, such as alcoholism and diabetes
mellitus , are likely to produce impotence, which interferes
with copulation. Other disorders, including anorexia nervosa
and some hormonal imbalances, can produce amenorrhea, or loss
of menstruation; this is also accompanied by loss of ovulation.
In other ways, however, the reproductive system is quite
robust, and couples who are in poor health are often able to
have offspring.
The main hazards to the reproductive system itself are the
sexually transmitted diseases and cancers of the different parts
of the reproductive system. The gonads, the prostate, and the
cervix are at particular risk.
testes: The male glands known as the testes are also sometimes
called the testicles, Latin for "little testes." The singular
for testes is testis. The testes are the male reproductive
glands, or gonads (GOH-nads), corresponding to the ovaries in
women.
Size and location The testes are somewhat smaller than chicken
eggs and roughly egg shaped. They are normally found in a
pouch of skin beneath the base of the penis called the scrotum.
Role The testes have two important products: the male hormone
testosterone and sperm. Testosterone is an endocrine hormone
released into the bloodstream. Sperm are produced in the testes
and stored in a sac in the body.
Conditions that affect the testes Sometimes, most often by
deliberate mutilation, a person is deprived of both testes;
this is called castration. If a boy is castrated before puberty,
he does not go through the changes of puberty.
Sometimes the testes remain inside a baby's body instead of
moving into the scrotum. One undescended testis may not be
much of a problem, although it can be corrected surgically and
often is. Two undescended testes produce sterility, apparently
because the temperature of the interior of the body is too
high for sperm production.
The place in the abdominal wall where the tube carrying sperm,
called the vas deferens, passes into the body is often weak,
and a hernia is a common result. Sometimes the hernia allows
part of the intestines to descend into the scrotum.
Cancer of the testes is rare but can be detected in its early
stages by self-examination for a lump. Any lump in a testis
may be harmful and should be examined by a physician. The
treatment is surgical removal of the testis. If done early
complications such as spread to the lungs can be avoided and
recovery is complete. The other testis produces enough
testosterone and sperm for normal function. Swelling of the
entire testis is usually not harmful and often goes away by
itself.
Some sexually transmitted diseases may invade the testes. In
addition, the scrotum may become involved in the fungal
infection known as jock itch.
Sometimes lack of the hormone testosterone can produce or
contribute to impotence. Production of the hormone tends to
decline in older men, often resulting in muscle weakness as
well.
penis: Male humans possess a multipurpose external organ
called the penis (PEE-nis). It contains the urethra
(yuu-REE-thruh), which is the tube used for expelling urine
from the body (in a female human, the urethra is in the abdomen).
That same male urethra is the passage for sperm-containing
semen during copulation.
Size and location Although the penis normally is soft and
flexible, it needs to be hard and stiff to enter a woman's
vagina during copulation. To achieve this transformation,
called erection, the penis is made from three different masses
of spongy tissue filled with many blood vessels. During
erection, which can take place spontaneously (usually during
sleep) or when there is sexual stimulation, the arteries
enlarge to admit more blood while the veins shut down to keep
the blood in the penis. Fluid pressure produces the erection.
Before erection a typical adult penis is about four inches long;
during erection it is about six inches long.
Role During copulation muscular contractions at the end of the
process expel about a teaspoonful or two of semen, which can
contain as many as 500 million sperm.
Conditions that affect the penis Inability to achieve erection
is termed impotence or erectile dysfunction. Certain sexually
transmitted diseases, especially syphilis and genital herpes,
often have a sore on the exterior of the penis as an early
symptom. Warts may be sexually transmitted or may simply
develop on the penis. Because cancer and syphilitic sores can
resemble warts, consult a physician about any growth on the
penis. Do not use over-the-counter wart treatments on the
penis as its thin and sensitive skin is easily damaged. Cancer
of the penis is rare, but it does occur and can spread into
the lymphatic system.
Other sexually transmitted infections, such as gonorrhea or
trichomonas, are primarily located inside the urethra. Often
the cause of infection of the urethra is unknown, and may be
labeled nonspecific urethritis by a physician. Infection of
the urethra can result in blockage, known as urethral stricture,
which is corrected by scraping its interior.
Sometimes an erection begins and will not go away, a condition
called priapism (PRY-uh-piz-uhm). This painful condition is
a serious disorder that requires emergency treatment. If not
corrected within three or four hours, priapism can cause
permanent impotence.
Hernias: Though heavy lifting is popularly thought of as the
cause of the physical breakdowns of body walls called hernias,
one does not necessarily have to do anything strenuous to get
a hernia. Some people are just born with a weakness in their
abdominal muscles. Sometimes a cough will produce a hernia at
a weak spot in the wall. Some babies are born with hernias.
Cause Thin sheets of muscle hold our internal organs in place.
Whenever part of an organ pushes through a weak spot or rip in
surrounding muscle, a hernia exists. Any organ can create a
hernia. For example, the stomach bulging up through a weak
spot in the diaphragm is called a hiatal (hy-AYD-uhl) hernia.
The hernias most people know about occur in the groin area,
where the abdominal wall meets the thighs. These inguinal
(ING-gwuh-nuhl) hernias occur when part of the intestine
pushes through the muscle wall. Many people are born with a
weak spot, called a congenital weakness, in this muscle wall,
but they may reach adulthood before a hernia finally appears.
Other people acquire a weak spot by straining abdominal
muscles until they tear, either through lifting too much
weight or lifting improperly. What finally causes the
intestine to push through is not always apparent, but coughing,
straining, lifting, and even accidents have brought on hernias.
Though women sometimes get inguinal hernias, they are much
more likely to suffer femoral (FEHM-uhr-uhl) hernias. Here
part of the intestine pushes down the canal carrying the femoral
artery into the thigh. Infants sometimes have umbilical hernias.
Part of the intestine bulges through the abdominal wall at the
point where the umbilical cord attaches.
Incidence Men are most likely to get hernias, and inguinal
hernias account for about three-quarters of all instances.
Overweight and pregnant women are more likely than other
women to suffer femoral hernias. Of all hernia types the
femoral variety is most likely to result in the dangerous
condition called strangulation.
Symptoms you are likely to notice You may suddenly experience
some discomfort when lifting heavy objects or bending over.
A telltale sign is a small, soft lump under the skin in the
groin area. Sometimes there is little pain in this early stage.
The hernia will often be reducible, meaning the intestine can
be gently pushed back in place by a physician and so make the
lump disappear. Get medical attention as soon as possible
after you notice a lump in the groin area.
Sometimes abdominal hernias push through at a point where they
protrude into the scrotum. Called an indirect inguinal hernia,
this type can be very painful and may make the scrotum swell.
Hernias left untreated can be extremely dangerous if they
become strangulated. Normally, when the intestine pushes
through the abdominal wall, the opening tends to get narrower
behind it. But if the opening gets small enough to cut off
the blood flow to the intestinal bulge, the hernia becomes
strangulated and swells up. Blood flow must be restored
quickly to prevent gangrene from developing. Immediate medical
attention is required. An untreated strangulated hernia may
result in death If you have a hernia that abruptly grows larger
and will not go back into place, it probably has become
strangulated. Usually there is sharp pain and nausea with a
strangulated hernia, but for the elderly especially there may
be no pain. Get immediate medical help when a hernia becomes
strangulated. Otherwise serious complications may develop.
Symptoms your physician may observe Physicians' training often
enables them to find small hernias during physical exams, even
before their patients have noticed them.
Treatment options Doctors may recommend wearing trusses and
corsets to keep a hernia from getting larger. But abdominal
(inguinal) hernias generally do not heal by themselves. Surgery
is the preferred treatment.
Stages and progress Usually hernias begin as a small lump,
perhaps no bigger than a marble. Over time pressure from
inside the abdomen gradually enlarges the opening in the
muscle wall. This allows more of the intestine to push through,
increasing the size of the lump. The hernia will probably be
reducible during this early stage.
prostate gland: Until recently the prostate gland was virtually
unknown to the public. Two factors have changed that and made
this small gland, found only in men, famous. One is that men
are beginning to live much longer - prostate enlargement,
which can cause difficulty with urination and pain, nearly
always occurs with sufficient age. The other is that prostate
cancer rates have risen dramatically, in part because of
better methods of detection but also due to greater longevity.
Size and location The walnut-sized gland is located at the
base of the urethra in men.
A physician can reach the prostate by inserting a finger into
the patient's rectum and feeling the gland's size and shape.
Older men should have a digital rectal exam every year or two.
Role The only known role of the prostate is the production of
a thick liquid that mixes with the sperm produced by the testes.
The combination, with sperm in place, is called semen.
The prostate also causes the blood to contain a compound
called prostate specific antigen (PSA). The larger or more
active the gland, the more PSA found in the blood. Thus older
men often have their PSA checked. If PSA levels rise sharply,
most physicians then use ultrasound to examine the prostate.
Conditions that affect the prostate gland Enlargement of the
prostate, or hypertrophy, without cancer is common. It leads
to difficulty in urination. Correction is often possible.
Bacteria can infect the gland causing prostatitis, a serious
condition that requires treatment with antibiotics.
Cancer is the most serious problem, but prostate cancer is
often slow growing and may not require immediate treatment.
If possible prostate cancer is found, different steps may be
taken depending on the indications and on the age and overall
health of the patient. Physicians usually use "watchful waiting,
" monitoring a slow-growing cancer frequently with PSA blood
tests and ultrasound. If PSA levels remain low, an older
patient is more likely to die from other causes than from
prostate cancer. If surgical removal of a cancerous prostate
is needed and is done early, it completely cures nearly 90% of
prostate cancer patients. Surgery at later stages cures more
than half of all prostate cancers. Removal of the gland may
lead to impotence in some cases.
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