Transcript Document 7786494

Exploring Lifespan
Development
Chapter 2
Prenatal Development
(Part 2)
Quick Quiz:
1.
2.
3.
4.
5.
6.
What is the purpose of a menstrual cycle?
T/F Women are born with all the eggs they
will ever have.
Conception happens where in a woman’s
body?
T/F A woman is pregnant for 10 months.
The most dramatic changes in our
development occur when?
T/F All embryos start out as girls.
Prenatal Development is Divided
into 3 Periods:
1.
Period of the Zygote (1-2 weeks)
2.
Period of the Embryo (3-8 weeks)
3.
Period of the Fetus (9 weeks to birth)
(Germinal stage)
(Embryonic stage)
(stages of pregnancy/fetal development are also
referred to as trimesters, or 2 month increments)
1. Period of the Zygote:
Conception
Occurs

Cells
Divide 
Zygote travels
to uterus

Implantation
into
uterine wall
0 hours
36 hrs
3-4 days
1 week
From Conception to
Implantation
Internal Female Organs:
Uterus
Fallopian
Tube
Fallopian
Tube
Ovary
Ovary
(Via Laparoscopic Surgery)
Know:

The final step in the period of the
zygote is Implantation to the uterine
wall.
Why?
Implantation Facts: (the answer
to Why?)




The dividing cell or blastocyst will not
develop if it is not implanted, for it needs
nourishment from the mother.
Implantation takes about 1 week to complete.
Implantation triggers hormonal changes that
tell the woman’s body not to menstruate.
Once a Zygote is firmly implanted it is now
called an Embryo.
Cell Division & Implantation
(what it looks like)
Blastocyst
Blastocyst
hatching out of
the hard outer
shell before it
can begin to implant
Implantation! On to
the next phase
2. Period of the Embryo:





The embryos body structures and internal
organs develop.
Leg, arm buds appear, sensory systems and
the brain and nervous system have begun to
develop.
The embryo can sense its world, respond to
touch and is moving. (mom can’t feel it yet!)
Amniotic fluid cradles the embryo and the
umbilical cord nourishes it and connects it to
the mother’s blood supply.
Growth of the head takes precedence over
growth of the lower parts of the body
Period of the Embryo, cont.



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The heart begins to beat at 6 weeks of
pregnancy.
The placenta permits the embryo to
exchange nutrients with mother
Placenta filters oxygen/nutrients which
pass from mother to embryo and
permits carbon dioxide/waste products
to pass to the mother from the embryo.
Mother and embryo have separate
circulatory systems
The Placenta (In Pictures!)
Guess What Guys?


You all started out
as a female during
the embryo stage of
development!
At 9 weeks of
pregnancy your Y
chromosome kicked
in and here you are,
the vagina turned
into a penis.
Which Embie is A Human?
Dolphin
Water Buffalo
Komodo
Dragon
Whale
Mouse
Human
Embryo Development:
Weeks
3 through 8:

3 ½ wks: Neuronal development begins
8 wks: Neurons begin to fire!
6 wks: My heart beats!
1 inch long and
½ oz.
3. Period of the Fetus:




The longest prenatal period.
Further maturation of fetal organ
systems/dramatic gains in size.
Gender can be determined via
ultrasound.
Significant increase in brain maturity
means new behavioral capacities &
ability to regulate its own basic body
functions.
9-12 Weeks of Fetal Development

9 weeks

The brain signals the
fetus to kick, curl its
toes, open its mouth,
and suck its thumb.
Fingernails, toenails,
tooth buds and eyelids
that open and close are
formed.
12 weeks
3 inches, < 1 oz.
13-24 Weeks of Fetal
Development
16 wks
20 wks
22 wks
24-25 wks
13-24 Weeks of Fetal
Development

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Skin thickens and is covered with Vernix-which
protects it. A soft downy hair develops called
Lanugo which helps the vernix stick.
Movements are now strong enough for mom to
feel.
Alternates between periods of sleep/waking.
Fingers/toes completely formed
Fetus develops a temperament/activity level
Fetal hiccoughs common
Eyebrows, eyelashes and scalp hair emerge.
12 inches, 1.8 lbs.
What is the Age of Viability?


The point at which a
fetus can survive
outside the womb.
Usually between
23-24 weeks of
pregnancy.
22 weeks
25-38 Weeks of Fetal
Development

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
Fetus practices breathing
by breathing and
swallowing amniotic fluid
Heart/lungs capable of
sustaining independent
life.
Layer of fat is added to
aid in temperature
regulation
Fetus assumes head
down position.
19-20 inches, 7.5 lbs.
Question:

True or false:
Prenatal fetal movement can predict
infant activity levels after birth.
Critical Periods in Prenatal
Development:


There are specific times during prenatal
development when certain organs are
developing rapidly.
If there is exposure to a Teratogen
during these Critical Periods there can
be harm done to the developing
embryo/fetus.
Critical Periods in
Prenatal Development
Teratogens
Environmental agents that can harm the
developing embryo or fetus.
1.
2.
3.
4.
5.
STD’s
HIV/AIDS
Rubella
Toxemia
Rh Incompatibility
Teratogens, cont.

a.
b.
c.
d.
e.
Drugs taken by the parents
Heroin/Methadone
Marijuana
Cocaine
Alcohol
Cigarettes
Teratogens, cont.


Environmental hazards
Parental age
Know:

The embryo is generally more
vulnerable to exposure to teratogens
than the fetus.