Download Male Reproductive System

Science Sponge
• What is the name of the tubes that the
egg travels down to become fertilized?
• How long does it take for the zygote to
implant?
• What is the temperature needed for
semen to form properly?
Male Reproductive System
External
organs
• Penis
• scrotum
Internal
Organs
• Testes
• Various ducts
• Seminal vesicles
• Prostate gland
• Bulbourethral gland
Testes
• Paired walnut shaped
organs that are located in
the scrotum
• Consists of highly coiled
tubes called seminiferous
tubules, where sperm are
formed
• Leydig cells are scattered
between the seminiferous
tubules and produce
testosterone and other
androgens.
Why place the testes outside
the body?
• Normal sperm development must occur
at a lower temperature (2°C lower in
scrotum)
• Scrotum is a fold of tissue that develops
from the abdominal wall cavity
• Testes develop high in the abdominal
cavity and then descend into the
scrotum just prior to birth
• In some mammals,
such as rodents, the
testes are drawn back
into the abdominal
cavity between
breeding seasons.
• Some mammals that
have low body
temperatures
(monotremes, whales
and elephants) retain
their testes within the
abdominal cavity
permanently
Ducts
• From seminiferous
tubules, the sperm pass
into coiled tubes called
the epididymis
• It takes about 20 days
for sperm to pass
through the 6 meter
long tubes
• As they progress
through the epididymis,
the sperm become
motile (move) and gain
the ability to fertilize an
egg
• During ejaculation, sperm are propelled from
the epididymis through the muscular tubes of
the vas deferens ducts
• The vas deferens run from the scrotum
around and behind the urinary bladder, where
each joins a duct from the seminal vesicle
forming an ejaculatory duct that opens into
the urethra
• The urethra runs through the penis to the
outside environment (remember that both
urine and semen pass through the urethra)
Accessory Glands
• Three sets of glands that contribute
secretions to form semen (sperm and
secretions)
• Seminal vesicles- contribute most of the
volume of semen. Secretes mucus and
fructose, a sugar which provides
nutrients to sperm
• Prostate gland- secretes anticoagulant
enzymes and nutrients
• Bulbourethral glands- secretes a mucus
that neutralizes any acidic urine left in
the urethra
Penis
• Composed of 3 cylinders of spongy
erectile tissue derived from modified
veins and capillaries.
• During sexual arousal, the erectile
tissue fill with blood from arteries.
• As tissue fills, increasing pressure seals
off the veins that drain the penis
causing it to engorge with blood and
stiffen.
Semen
• Approximately 2-5 mL of
semen is released with each
ejaculation and carries 50-130
million sperm.
• Once in the female
reproductive tract,
prostaglandins in the semen
cause thinning of the mucus
and stimulate uterine
contractions to move the
sperm toward the waiting egg
Growth and Development
• The fertilized egg (zygote) becomes an
embryo once the first cell division
occurs.
• 11-12 days after fertilization,
implantation occurs. This means the
baby has implanted itself on the uterine
wall of the mother.
Growth and Development
• The placenta is a special two-way
exchange organ that provides the baby
with nutrients, and oxygen.
Growth and Development
• A normal pregnancy lasts for 280 days
• At the end of week 4 implantation is
complete and the woman is pregnant.
The embryo’s blood begins to form.
Growth and Development
• Weeks 5 to 8 a tiny amniotic sac of fluid
surrounds the baby to protect from
bumps and injury.
• The umbilical cord develops along with
heart, brain, other organs, and blood
vessels. Limbs are also in development.
Growth and Development
• At week 9-16 the baby is officially called
a fetus. The muscles of the baby grow
stronger and the baby grows rapidly
during this stage.
Growth and Development
• At about 25 or 26 weeks the fetus has
developed lungs although the fetus still
gets oxygen from its mother. By 32
weeks the fetus can open and close its
eyes. By 36 weeks the fetus is ready to
be born.
Pregnancy is full of
Surprises