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Human Reproductive
System Review
Sexual Development
• After birth, the gonads produce
small amounts of sex hormones that
continue to develop the reproductive
organs
• Neither testes nor ovaries are
capable of producing active
reproductive cells until puberty
• Puberty = period of rapid growth and
sexual maturation beginning between
ages 9-15 when the hypothalamus
signals the pituitary gland to produce
increased levels of folliclestimulating hormone (FSH) and
Male Reproductive
System
• The release of FSH and LH
stimulates the testes to produce
testosterone, a steroid that
stimulates target cells all over
the body producing secondary
sex characteristics (facial and
body hair, body growth, deeper
voice)
• FSH and testosterone stimulate
Male Reproductive
System
Sperm Formation
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MEIOSIS forms sperm in gametes
Sperm forms in testes
Scrotum keeps cooler than rest
Semen is sperm plus protecting fluid
Semen leaves testes through the vas
deferens (sperm ducts) to the
urethra before it exits.
Secondary Sexual
Characteristics - Male
• Produced by testosterone
– Deeper voice
– Chest and facial hair
– Lengthen bones
– Increased size of testes for
sperm production
Female Reproductive
System
• The structures of the female
reproductive system produce
eggs as well as prepares the
female’s body to nourish a
developing embryo
– Ovaries – produce ova (eggs)
from follicles
– Fallopian tubes (oviduct) –
carry eggs from ovaries to
Female Reproductive
System
Mrs. Degl
Ovum Formation
• MEIOSIS forms the eggs (ova)
• Eggs are formed before birth
• 1 egg per month is matured and
released from ovaries, most of
the time
• Eggs travel through the fallopian
tube where they may become
fertilized
Secondary Sexual
Characteristics - Female
• Induced by increased LH, FSH,
estrogen, and progesterone
hormone levels
– Pubic hair
– Widen pelvis
– Enlarge mammary tissue
(breasts)
– Begin menstrual cycles
The Menstrual Cycle
Section 39-3
Fertilization
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Occurs in upper 1/3 of Fallopian tube
Only 1 sperm can fertilize an egg
Fertilized egg = zygote
An average woman is pregnant
(gestational period) for 9 whole
months. That is 40 weeks. Babies
can survive if they are born earlier,
but they may have complications due
to being premature.
Implantation
• Fertilized eggs are implanted into
thick walls of uterus
• Chorion membranes dig into uterus to
form placenta
• Zygote grows into an embryo
• Embryo gets air and nutrients
through the umbilical cord
• Once pregnant, progesterone levels
stay high in mom
• Mom’s uterus grows with the baby
BLASTULA TO
GASTRULA
BLASTOCYST
GASTRULA
THREE LAYERS
OF CELLS ARE FORMED.
THIS IS CALLED
Animations:
DIFFERENTIATION
http://learningobjects.wesleyan.edu/gastrulation/animations.php?a
ni=3D
http://www.hhmi.org/biointeractive/media/human_emb_devlg.mov
CELLS PINCH INWARD
A.K.A. INVAGINATION
1st Trimester =
1st 12 weeks
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Placenta forms
Heart develops first
Neural tube develops
All body systems appear by
Week 8 – Now a Fetus
Fertilization and
Implantaton
Section 39-4
Fallopian tube
Day 2
Day 3
Day 1
Day 4
4 cells
Morula
Day 7
Blastocyst
2 cells
Fertilization
Zygote
Day 0
Implantation of
blastocyst
Uterine wall
Ovary
Egg released
by ovary
Figure 39–20 The
Placenta
Section 39-4
Amniotic sac
Placenta
Umbilical cord
Fetal
portion of
placenta
Maternal
portion of
placenta
Villus in chorion
Amnion
Uterus
Amnion
Umbilical cord
Maternal
artery
Umbilical arteries
Umbilical vein
Maternal
vein
2nd Trimester =
up to 24 weeks
• Most growth
• Looks more like a baby
• Some preemies survive at this
stage
3rd Trimester
= Up to 40 weeks
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More growth
Kicking, rolling, stretching
Eyes open – Week 32
Lungs mature
Rotates to head-down
position, unless baby is
breech
Birth
• Labor
– Uterine contractions begin
– Cervix dilates to 10 cm.
• Birth
– Uterus pushes baby through vaginal
canal
– Placenta delivered after baby
– Cesarean Section (c-section) is a surgery
that cuts through the uterus to deliver
the baby if it cannot be born vaginally
Multiple Births?
• Fraternal twins = when 2 eggs are released
and fertilized by 2 sperm during the same
cycle
– Not identical because different eggs
fertilized by different sperm
• Identical twins = when 1 zygote splits
producing 2 embryos
– Identical because contain genetic
information from same egg and same
sperm