(Students: Bolded, italicized, and underlined sections will be on the exam)
The Reproductive System:
I. Function of the System:
The purpose of the reproductive system is to create offspring using sexual
reproduction. It allows for the sperm from the male to join and fertilize the egg in
the female. This provides for greater genetic variation than asexual reproduction
would provide.
II. The Main Parts of the System:
Overview: The testes in the male store sperm, and the ovaries in the female store the
eggs. During human sexual reproduction, the male penis ejaculates inside of the
female vagina, releasing semen into the uterus. The semen contains sperm which finds
the egg(s) and fertilizes them. Once an egg is fertilized by one sperm, no other sperm
can enter it because its outer surface become hardened. The fertilized egg will then
undergo mitosis and develop into the baby.
The Male Reproduction System: The male reproductive system is shown below. This
system produces sperm and delivers it to the female reproductive system. The major
parts of the male reproductive system include the testes, prostate gland, urethra, and
penis.
A. Testes: The testes (singular, testis) make sperm and testosterone. Testosterone
is the principal male sex hormone; it regulates the production of sex cells and
the development of male characteristics. The testes produce and store the
sperm. The males testis is packed with tightly coiled tubes, called somniferous
tubules, which can be up to 70 cm. (28 inches) long. Thousands of sperm cells
mature inside these tubules every second. The sperm are then passed into the
epididymis, cord like structure at the back of the testes, where the maturing process
is completed. The testes are located in the scrotum, which keeps the testes away
from the body, helping to prevent the sperm from being destroyed due to excess
heat. Sperm are produce throughout a male’s life.
B. Prostate Gland: The prostate gland is responsible for producing fluids that mix
with sperm to create semen. Semen is the mixture or sperm and fluids. Semen
then passes through the urethra.
C. Urethra: The urethra carries semen out of the body through the penis. It also
carries urine from the urinary system.
D. Penis: The penis is the organ that transfers the sperm outside of the male and
into the female’s body. It is is actually made of two parts: the shaft and the glans.
The shaft is the main part of the penis, and the glans is the tip (sometimes called the
head). All boys are born with a foreskin, a fold of skin that covers the glans. Some
boys have a circumcision (usually done within a few days after birth), which means
that a doctor or a clergy member cuts away the foreskin. Whether a boy is
circumcised can depend on the preference of the individual family, the part of the
world he lives in, or his family's religion. Boys who have circumcised penises and
those who do not are no different: all penises work and feel the same, regardless of
whether the foreskin has been removed. At the end of the glans is a small slit or
opening by which urine or sperm pass.
The Female Reproduction System: The female reproductive system is shown below.
This system produces eggs which are fertilized by the male’s sperm. The major parts
of the female reproductive system include the ovaries, oviduct, uterus, and vagina.
A. Ovaries: The ovaries produce eggs and the hormones which cause sex
characteristics in women. A normal woman has two ovaries which are located in
the lower part of the female’s abdomen, about 4 or 5 inches down from a girl's
waist, and each one is about the size of an almond in its shell. They are shaped
like eggs and measure about 1 1/2 to 2 inches in length in a grown woman. The
ovaries sit on either side of the uterus, and special tissue keeps them connected to
the fallopian tubes. Each woman's ovaries contain about 1 million ova (eggs).
A baby girl is born with all these eggs, but it isn't until puberty that the eggs
begin to be released. Usually, after a girl reaches puberty, one ovum (or egg) will
be released from an ovary each month until she begins menopause. An egg pops
out of the ovary and enters the fallopian tube, where it makes its journey to the
uterus.
B. Oviduct (Fallopian Tubes): The oviduct is a narrow tube that leads from the
ovaries to the uterus. It is where fertilization between the sperm and egg can
take place. The tubes are attached on one end to either side of the uterus, and
they extend out and back from the uterus. Each oviduct (fallopian tube) is about
4 inches long and is about as wide as a piece of spaghetti. Within each tube is a
tiny passageway no wider than a sewing needle. At the other end of each
fallopian tube is a fringed area that looks like a funnel. This fringed area wraps
around the ovary, but is not completely attached to the ovary. When an egg pops
out from the ovary, it enters the fallopian tube. Once the egg is in the fallopian
tube, tiny hairs in the tube's lining help push the egg down the narrow
passageway toward the uterus.
C. Uterus: If the egg joins with sperm in the fallopian tube and is fertilized, it will
attach to the inner lining (endometrium) of the uterus and begin to develop
into a baby. About 9 months later, a mother gives birth to her baby. If the egg
isn't fertilized, it is washed away along with the blood and tissue of the
endometrium that grows on the inside walls of the uterus each month, otherwise
known as a menstrual period. The uterus has thick muscular walls and looks like
an upside-down pear. Normally, the size of a woman's uterus is about the same as
her closed fist, and the walls of the uterus touch one another. The uterus contains
some of the strongest muscles in a woman's body. These powerful muscles are
able to expand and contract in order to accommodate a growing baby and to
then help push the baby out during labor.
More on menstruation: The uterus is also where menstruation begins each month - it
builds up its inner lining, known as the endometrium, with extra blood and tissue,
anticipating that an egg might be fertilized by sperm entering the woman's body.
The fertilized egg can then attach to the endometrium and pregnancy occurs. If
an egg is not fertilized, the uterus sheds this extra blood and tissue, which comes
through the cervix and out of the vagina as a menstrual period.
D. Vagina: The vagina is a canal that leads from the uterus to the outside of the
female’s body. The cervix is a sphincter muscle that separates the uterus from
the vagina. The vagina is a muscular, hollow tube that is about 3 to 5 inches long
in a grown woman. Because it is made of muscle, it can expand and contract. Its
ability to become wider or narrower allows the vagina to accommodate something
as slim as a tampon and as wide as a baby. The opening of the vagina is
completely or partially covered by the hymen, a thin piece of tissue that has one
or more holes in it. Hymens are often different from person to person.!Most
women find their hymens have stretched or torn after their first sexual experience.
Some women who have had sex!do not have much of a change in their hymens.!If
the hymen is stretched or torn, it may bleed a little, but this usually causes little, if
any, pain.
III. Interactions With Other Systems:
Some examples of systems that directly interact with the system include:
• The Urinary System: The urethra allows both sperm and urine to travel through it.
• The Endocrine System: The male testes and female ovaries produce hormones for
the endocrine system that cause sex characteristics. They also produce sperm and
eggs for the reproductive system.
IV. Some Disease and Disorders:
• Vulvovaginitis: Vulvovaginitis, an inflammation of the vulva and/or vagina, is the
most common childhood gynecological problem. In young girls, it is most often
caused by irritating substances (such as laundry soaps or bubble baths), and may
be exacerbated by poor personal hygiene (such as wiping from back to front after
a bowel movement). Symptoms include redness and itching in the vaginal area and
sometimes vaginal discharge. Vulvovaginitis can also be caused by an overgrowth
of candida, a yeast-like fungus normally present in the vagina, although yeast
infections are more common in teenagers and adults.
• Vaginal Bleeding: Vaginal bleeding, when it occurs in premenstrual girls, is most
commonly due to the presence of a foreign body in the vagina, such as wadded-up
toilet paper. Less often it may be due to urethral prolapse, a condition in which the
mucous membranes of the urethra protrude into the vagina and form a mass that
bleeds easily. It can also be due to an injury or sexual abuse.
• Phimosis: Phimosis is a tightening of the foreskin of the penis, which is common in
newborns and young children and usually resolves without treatment. If it
interferes with urination, circumcision may be recommended.
• Micropenis: Micropenis is a rare disorder where the penis, although normally
formed, falls well below the average size, as determined by standard measurements.
Testicular trauma. Even the slightest injury to the testicles can cause severe pain,
bruising, or swelling. Most testicular injuries occur when the testicles are struck,
hit, kicked, or crushed, usually during sports. To protect their testicles from trauma,
boys and men should always wear athletic cups during contact sports.
• Testicular Torsion: This testicular problem occurs most frequently in males
between the ages of 12 and 18. Within the scrotum, the testicles are secured by a
structure called the spermatic cord. When the testicle twists on this cord, the blood
supply to the testicle is cut off. Torsion might occur as the result of trauma to the
testicles, strenuous activity, or for no apparent reason at all. In the United States,
testicular torsion occurs in one out of 4,000 males younger than 25.
• Undescended Testicles: A male baby may be born with his testicles not having
descended into the scrotum. The testes form in the abdominal cavity in the early
stages of fetal development, and then descend in the month before birth. If the
testicles do not drop by themselves, surgery can bring them down.
• AIDS: AIDS!is one of the most serious, deadly diseases in human history. AIDS is
caused by the!HIV virus (human immunodeficiency virus). HIV destroys a type of
defense cell in the body called a CD4 lymphocyte. Normally these lymphocytes are
part of the body's immune system, the defense that fights infectious diseases. But
as the number of!lymphocytes drop!because of HIV,!people with the virus begin to
get serious infections that they normally wouldn't. That is, they become immune
deficient and are said to have acquired immune deficiency syndrome (AIDS).
About 20 years ago, the first cases of AIDS were identified in San Francisco and
New York. Since that time,!more than 20 million!people have died!of AIDS-related
illnesses worldwide, and millions more are living with the disease.
• Various Sexually Transmitted Diseases: There are dozens of sexually transmitted
diseases besides AIDS all of which have various symptoms and treatment. All of
these can be prevented by abstinence (condom use decreases the chances of
transmission). You will study these in depth in 8th grade during the sex ed unit.