9/6/2017 1 Prenatal Development and the Newborn Period How Children Develop Chapter 2 Overview Prenatal Development The Birth Experience The Newborn Infant Prenatal Development Conception, Developmental Processes, and Early Development Fetal Behavior, Experience, and Learning Hazards to Prenatal Development Conception Results from the union of two gametes, the egg and the sperm Gametes produced through specialized cell division, meiosis: Each has only half the genetic material of all other normal cells in the body
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9/6/2017
1
Prenatal Development
and the Newborn Period
How Children Develop
Chapter 2
Overview
Prenatal
Development
The Birth
Experience
The Newborn
Infant
Prenatal Development
Conception, Developmental
Processes, and
Early Development
Fetal Behavior, Experience,
and Learning
Hazards to Prenatal
Development
Conception
Results from the union of two gametes, the egg and the sperm
Gametes produced through specialized cell division, meiosis:
Each has only half the genetic material of all other normal cells in the
body
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Prenatal Development
1. Ovum (1/175 inch) + Sperm (1/500 inch) = Baby
1. Of 360 million released by male, only 100 reach
ovum.
Sperm live for 48 hours – they swim for 6 hours, they lie in wait.
Prenatal Development
1. Ovum (1/175 inch) + Sperm (1/500 inch) = Baby
1. Of 360 million released by male, only 100 reach
ovum.
Sperm live for 48 hours – they swim for 6 hours, they lie in wait.
Sperm Competition
Sex Differences
Begin at Conception
Approximately 120 to 150 males are conceived for every 100 females
How and why?
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Sex Differences
Begin at Conception
Approximately 120 to 150 males are conceived for every 100 females
How and why?
Y chromosome sperm than X chromosome sperm
Male embryos are rates, and boys are more vulnerable to developmental disorders and illness
Sex Differences
Begin at Conception
The Zygote
The fertilized egg, or zygote, has a full complement of human genetic material, half from each parent
Marks the beginning of the three periods of prenatal development
Germinal: Begins with conception and lasts until the zygote becomes implanted in the uterine wall. Rapid cell division takes place.
The Zygote
Embryonic: Following implantation, major development occurs in all the organs and systems of the body.
Fetal: Continued development of physical structures and rapid growth of the body. Increasing levels of behavior, sensory experience, and learning.
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Periods of
Prenatal Development
Germinal(conception - 2 weeks)
Embryonic(3rd - 8th week)
Fetal(9th week - birth)
The Cells
Four major developmental
processes transform a
zygote into an embryo and then into a fetus
1. Cell division results in the proliferation of cells
2. Cell migration is the movement of cells from their
point of origin to somewhere else in the embryo
3. Cell differentiation transforms the embryo’s
unspecialized stem cells into roughly 350
different types of cells
4. The selective death of certain cells, or
apoptosis, also enables prenatal development
The Cells
Four major developmental
processes transform a
zygote into an embryo and then into a fetus
1. Cell division results in the proliferation of cells
2. Cell migration is the movement of cells from their
point of origin to somewhere else in the embryo
3. Cell differentiation transforms the embryo’s
unspecialized stem cells into roughly 350
different types of cells
4. The selective death of certain cells, or
apoptosis, also enables prenatal development
The Role of Hormones
Hormones play a crucial role in sexual differentiation All human fetuses can develop either male or
female genitalia, depending on the presence or absence of testosterone
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The Role of Hormones
Hormones play a crucial role in sexual differentiation All human fetuses can develop either male or
female genitalia, depending on the presence or absence of testosterone
One of the many ways in which the fetus acts as an instigator of its own development
The Blastocyst
By the 4th day after conception, the
zygote arranges itself into a hollow
sphere of cells with a bulge of cells,
the inner cell mass, on one side
The inner cell mass eventually forms
into the embryo
Protecting the Fetus
The placental membrane is a barrier against
some, but not all toxins and infectious agents
The amniotic sac, a membrane filled with
fluid in which the
fetus floats,
provides a
protective
buffer for
the fetus
The Fetus: An active contributor
to its own development
By 12 weeks after gestation, most of
the movements that will be present at
birth have appeared
Swallowing amniotic fluid promotes the
development of the palate and aids in the
maturation of the digestive system
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The Fetus: An active contributor
to its own development
By 12 weeks after gestation, most of
the movements that will be present at
birth have appeared
Swallowing promotes the
development of the palate and aids in the
maturation of the
Pulling in and expelling small amounts of
help the
become functional
Sensation
The sensory structures are present
relatively early in prenatal development
and play a vital role in fetal development
and learning
The fetus experiences tactile stimulation as
a result of its own activity, and tastes and
smells the amniotic fluid
It responds to sounds from at least the
6th month of gestation
Prenatal visual experience, however, is
negligible
Fetal Learning
At 32 weeks’
gestation, the
fetus decreases
responses to
repeated or
continued
stimulation, a
simple form of
learning called
habituation
Fetal Learning
Newborn infants
have been shown to
recognize rhymes
and stories presented
before birth
Newborns also prefer
smells, tastes, and
sound patterns that
are familiar because
of prenatal exposure
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Miscarriage
By far the most common misfortune in
prenatal development is spontaneous
abortion (miscarriage)
Miscarriage
By far the most common misfortune in
prenatal development is spontaneous
abortion (miscarriage)
Around or more of conceptions result
in very early miscarriages, and about
of pregnancies of which women are
aware are miscarried
The majority of embryos that miscarry
very early have severe defects
Teratogens (Greek: teras – monstrosity):
Environmental agents that
have the potential to cause
harm during prenatal
development
Timing is a crucial factor
in the severity of the
effects of potentially
harmful agents
Many agents cause
damage only if
exposure occurs during
a sensitive period in
development
Sensitive Periods
p. 60
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Teratogens
What effects impact of a teratogen?
Amount and length of exposure.
Genetic make-up of mother and baby.
Multiple negative factors (poor nutrition,
no medicine).
Age of organism at time of exposure.
Teratogens
What effects impact of a teratogen?
Amount and length of exposure.
Genetic make-up of mother and baby.
Multiple negative factors (poor nutrition,
no medicine).
Age of organism at time of exposure.
Teratogens include legal as well as
illegal substances...
Some Environmental Hazards
to Fetus or Newborn
p. 62
Any drug that mother takes affects fetus.
Good example is the anti-naseau thalidomide.
But, many pregnant women take unprescribed drugs:
Aspirin: linked to low birth weight (LBW), infant
death, poor motor development…and on and on.
Caffeine (heavy use): linked to LBW, miscarriage,
irritable and vomiting newborns.
Prescription and
non-prescription drugs
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Teratogens
Maternal alcoholism can lead to fetal alcohol syndrome
(FAS), which is associated with mental retardation, facial
deformity, and other problems
FAS is the leading cause of mental retardation in western civilization.
Teratogens
Cigarette smoking during
pregnancy is linked to
retarded growth and low
birth weight
Cigarette smoking has also
been linked to SIDS (sudden
infant death syndrome),
although the ultimate causes
of SIDS are still unknown
Parents can reduce the risk by not smoking, putting babies to
sleep on their backs, using firm mattresses and no pillows,
Physical: LBW, physical defects, breathing problems, drug
addicted
Psychological: Less attentive, motor development slowed.
Marijuana – less is known and mixed findings.
Evidence of disturbed sleep, startles, tremors.
Maternal Factors
The age, nutrition, disease, and stress-level of the mother have an impact on prenatal development
Infants born to girls 15 years or younger are three to four times more likely to die before their first birthday than are those whose mothers are in their 20s
Inadequate nutrients or vitamins such as folic acid can have dramatic consequences (e.g., growth of the fetal brain)