Download Pregnancy

Pregnancy
Chapter 4
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Pregnancy
• New human enters the world
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9 months as baby grows
Lots of changes
Genes come from mom and dad
Control how babies grow and develop
even before they are born
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Conception
• Cell = is the smallest unit of life that is able
to reproduce itself
• Life begins with joining of two separate
cells one from the male and one from the
woman
• Sperm – male sex cell
• Ovum – female sex cell – egg
• Conception –union of the ovum and sperm
cells
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• Zygote – single cell formed at conception;
also called a fertilized egg
• Fallopian tubes – two hollow tubes that
connect to the uterus and have fingerlike
projections that reach toward each ovary
• Uterus – organ in which the baby develops
and is protected until birth
• Genetic factors- traits that are passed
though the genes
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Process
• Hormones cause follicles to grow and fill
with fluid
• Ovum is released once a month
(ovulation)
• Travels toward fallopian tubes
• Ovum moves through the tubes ready to
join the sperm
• Dozen sperm approach the ovum and only
one enters
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Genetic Factors & the Unborn Baby
• Genetic factors are passed onto the baby
• Genetic blueprint gives cells instructions
for family-like traits
• Baby boy’s cells receive instructions on
whether he will be bald later in life for
example
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Heredity & Steve
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Steve is 5
Asks many questions
Shares traits with other 5 yr olds
His DNA is his own
Chromosomes – threadlike structures that
carry genes in living cells
• Contain information nature needs to make
Steve human
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Chromosome & Genes
• Human baby has 46 chromosomes
• 23 from mom and 23 from dad
• One gene can decide a trait or many
genes can decided
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Dominant & Recessive Genes
• Dominant – traits that
always show in a
person even if only
one gene of the pair
is inherited for that
trait
• Recessive – traits that
typically do not show
in a person unless
both genes for the
trait are inherited
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• People can pass on traits that don’t show
up in the parents
• Color blindness and hemophilia are
example of a single recessive gene
• People have both dominant and recessive
genes for height
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Sex Chromosomes
• Females have XX
• Males have XY
• Sex chromosome in the father’s sperm
determines whether a child will be a boy or
a girl
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Multiple Pregnancy
• Two or more babies develop
• Far less common than single pregnancies
• Fertility drugs can cause multiple
pregnancies
• Twins = 1 of 35 births
• 3 or more = 1 in 540
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Fraternal Births
• Two ova and differ in genetic make up
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Twins, triplets, etc
May or may not be same gender
Look different at birth
Chorion membrane surrounds each baby
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Identical Births
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Single ovum
Twins, triplets, etc
Very similar in appearance
May be mirror twins
Same gender
Share one chorion membrane
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Mixed Types
• Triplets are often mixed pregnancies
• Two identical, one fraternal
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Stages in Prenatal Development
• Development that takes place between
conception and birth
• Germinal stage –first stage of prenatal
development, which lasts about two weeks
after conception
• Conception marks the beginning of the
germinal stage
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• Zygote remains a single cell for about a
day and a half
• 3rd day it is a hollow ball of 32 cells
• Enters the uterus where it divides for 3
more days (free floating)
• 10 to 12 days the ball is embed in the wall
of the uterus
• See page 120-121 figure 4-12
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• Chorion and amnion (fluid filled sac) begin
to form
• Placenta (organ filled with blood vessels)
• Develop against the wall of the uterus
• Umbilical cord contains 3 blood vessels
that connect the child with the placenta
• See page 122 figure 4-13
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Embryonic Stage
• Second stage of prenatal
development
• Most critical stage of
pregnancy
• Almost all body systems
develop during this stage
• Lasts 6 weeks
• Baby is now called an
embryo
• Changes happen quickly
• Tiny arms, legs, fingers,
toes and a face
• Major organs are present
• Cartilage is soft, elastic,
flexible tissue that
provides structure
• Receives both good and
harmful substance
through placenta
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Fetal Stage
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Third stage
Last 9 weeks after conception until birth
Baby now called a fetus
All parts of the body mature
Overall size increases
Mother looks pregnant
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Two Milestones in Fetal Stage
• 1. Hear baby’s heartbeat for first time
• Will begin to feel the baby move
(quickening)
• Baby can turn, swallow, and suck its
thumb
• 2. At 7 months (age of viability)
• Most babies could survive if they were
born (28th week of pregnancy)
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Although baby is viable
The closer to the nine months the better
Baby’s lungs become stronger
In the ninth month fetus receives
immunities from mom
• Baby turns head down for delivery
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Using Your Knowledge
• 1. Technology/Science. Go on line to
research genetic counseling. What job
duties do professionals in this field have,
and what technologies do they use to
investigate which genes a child might
inherit from parents? Use a computer to
compose a short report on your findings.
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• 2. Science. Collect pictures of identical
and fraternal siblings and note how alike
or different they are. Try to find various
pictures of the same people taken over
several years.
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Making Observations
• 1. Observe your physical features. Which
features seem to come from your mother’s
family and which from your father’s family?
Which features do you share with other
relatives?
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• 2. Observe brothers and sisters. Which
characteristics do they share? How are
they different?
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