|
Reproductive system
Reproductive system: Humans, like other mammals, reproduce
sexually. This means that both the male and the female
participate in producing another individual.
Size and location The male and female reproductive systems
differ in fundamental ways.
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.
|
