Human Reproductive
System
Living Environemnt
Puberty – when a person becomes sexually
mature and is capable of reproduction.
 Male Reproductive System:
- Gonads = Testes
- Gametes = Sperm Cells
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Sperm Cells made in the testes
Testes - also act as an endocrine gland secreting
testosterone, which is responsible for
secondary sex characteristics. Body Hair,
muscle development, deeper voice…
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Each testis consists of small coiled
tubes called the Seminiferous
Tubules. Immature sperm are
produced in the seminiferous
tubules. After being produced sperm
move to the epididymis where they
are stored. Lave the epididymis
through the vas deferens.
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The two vas deferens meet at the
urethra. Glands secrete fluids into
the sperm. The mixture or fluids and
sperm = semen. The semen passes
through the urethra by the process of
ejaculation. Urine is blocked shortly
before and after ejaculation.
Female Reproductive System:
- Gonads = Ovaries
- Gametes = Eggs
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Ovaries make Eggs
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Ovaries – also secret female hormones
including estrogen, which is responsible
forsecondary sex characteristics. Breast
Development, Broadened Pelvis…
2 ovaries that contain about 200,000 tiny egg
sacs called follicles. Each Follicle contains 1
immature egg. These immature eggs are
present at the time of birth.
When one of the follicles ruptures the egg
is released at the surface of the ovary =
ovulation. First occurs at puberty.
 Oviduct or Fallopian Tube = tube with
funnel like opening. Ciliated cells draw
the egg into the oviduct. Passes through
the oviduct into the uterus. Uterus =
thick walled muscular pear shaped organ.
 Once the egg is in the uterus it can be
fertilized by a sperm cell.
 Cervix connects uterus to the Vagina.
During Pregnancy the child will pass
through the cervix and leave the mother
through the Vagina.
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Menstrual Cycle
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Mature egg is developed and released from one
of the ovaries approximately every 28 days.
The walls of the uterus have been building up
preparing to accept the egg.
If the egg is not fertilized the wall of the uterus
breaks down. Material from the wall and the
unfertilized egg and eliminate from the body.
The cycle begins again with the maturing of
another egg.
This process is called the menstrual cycle.
Begins during puberty age 12-15.Controled by
hormones.
Stages of the Menstrual Cycle:
 Follicle Stage = FSH (Follicle) Stimulating Hormone is secreted by
the pituitary gland. FSH causes several follicles to begin to
develop. Usually only one matures. As the follicle develops it
secretes estrogen. Estrogen causes the uterine lining to become
thicker.Usually lasts about 10 days
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Ovulation = High level of estrogen in the blood causes the pituitary
gland to decrease the secretion of FSH and begin the secretion of
LH (Luteinizing Hormone).When LH levels reach a certain point
ovulation occurs. Follicle ruptures. Usually Takes place in the
middle of the menstrual cycle.
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Corpus Luteum Stage = After ovulation LH causes the ruptured
follicle to fill with cells forming a yellow body called the corpus
luteum. Corpus Luteum begins to excrete the hormone
progesterone, which continues the growth of the uterine lining.
Lasts about 14 days.
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Menstruation = No fertilization occurs
Menstruation = No fertilization occurs
 LH levels drop off
 Corpus Luteum breaks down
 Progesterone levels drop off
 Thick lining of uterus can not be maintained so
it breaks down
 The extra lining, unfertilized egg, and a small
amount of blood pass out the body through the
vagina.
 Lasts about 4 days
 Pituitary gland begins to produce FSH again
 New egg begins to develop and cycle starts all
over again
Menstrual Cycle will stops temporarily during
pregnancy. Around middle age (45-50) will
stop permanently = menopause.
Fertilization and
Development:
 Sex - Hundreds of
millions of sperm
are ejaculated
into the vagina.
Travel through
the cervix, across
the uterus, and
into the oviducts.
If an egg is
passing through
the oviducts
fertilization may
occur. Zygote is
formed.
Implantation – Zygote undergoes
cleavage developing into a blastula. At
the same time it is moving down the
oviduct toward the uterus. 5-10 days
after fertilization zygote enters the
uterus. Outer cells of the zygote secrets
enzymes that eat away the lining of the
uterus. Zygote attaches to that spot.
 Three germ layers develop. From this
point on the developing human is called
an Embryo. After 8 weeks the developing
human is called a fetus.
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Week 3
Week 4
Week 5
Week 6
Week 7
Week 8
During pregnancy the menstrual cycle is
stopped. A hormone is secreted that
prevents the break down of the corpus
luteum, which continues to secrete
progesterone, which maintains the thick
lining of the uterus.
 In Vitro fertilization – fertilization occurs
outside the body in a lab then zygote is
placed back in the female’s uterus to
develop.
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Between fertilization
and implantation
embryo survives off
of food stored in the
egg. After
implantation embryo
receives food and
oxygen from the
mother through the
placenta.
 Outer layer of
blastula forms
chronin. Chronin =
membrane that
surrounds the
embryo. Chronin villi
project into the
uterine lining and
form the placenta.
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Placenta – has fetal side (fetus’s blood)
and maternal side (mothers blood).
Mother’s blood and Fetus’s blood never
mix. Fetus is connected to the placenta by
the umbilical cord. Carries nutrients and
oxygen to the fetus, waste out of and
away from the fetus. Placenta protects
the fetus from harmful agents in the
mother’s blood. Some things can still pass
through the placenta = some viruses,
alcohol, nicotine, most drugs.
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Extraembryonic Membranes – same as
birds and reptiles, different purposes.
Chronin = implantation. Amnion = filled
with amniotic fluid, which surrounds and
protects the fetus. Allantois and yolk sac
= develops into the umbilical cord.
Birth:
 Gestation period = length of pregnancy. In humans it is
about nine months.
 When the fetus is ready to be born the uterus begin
slow rhythmic contractions = labor.
 Same time cervix begins to enlarge. It must expand
from 1 to 2cm to 11 or 12cm for birth to occur.
 When the cervix is completely expanded the amniotic
membrane bursts lubricating the birth canal.
 Contractions force the fetus, head first, from the uterus
into the vagina and out of the mother’s body.
 Once outside the mother’s body the umbilical cord is
still attached. It is tied and cut leaving a scar = naval
or belly button.
 Contractions continue after birth which expel the
placenta and amnion = afterbirth.
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Fraternal Twins – two
eggs become fertilized,
imbed separately and
develop separately.
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Identical twins – a fertilized egg
divides into two embryos at an early
stage of development. Each embryo
then forms separately. Pregnancy
drugs.
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Postnatal Development:
Birth
Growth
Puberty
Adult
Aging
Death