|
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.
--------------------------------------------------------------------------
|
