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Human Growth and Development

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Title: Human Growth and Development


1
Human Growth and Development
  • Chapter Four Prenatal Development and Birth

PowerPoints prepared by Cathie Robertson,
Grossmont College Revised by Jenni Fauchier,
Metropolitan Community College
2
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3
From Zygote to Newborn
  • Germinal periodfirst 14 days
  • Embryonic period3rd through 8th weeks
  • Fetal period9th week through birth

4
Process of Conception
5
Germinal The First 14 Days
  • Zygote divides and keep dividing (at least though
    3rd doubling they are the same)
  • At this stage (8 cells) differentiation begins
  • early stem cells take on distinct
    characteristics
  • they gravitate to locations, foreshadowing the
    type of cells they will become

6
Germinal The First 14 Days, cont.
  • At about a week after conception the multiplying
    cells separate into two masses
  • outer layer forms a shell (later the placenta)
    and the inner cells from a nucleus (later the
    embryo)
  • first task of out cells to achieve implantation
    embed themselves into the nuturant environment of
    the uterus
  • 60 of all natural conceptions fail to implant
    70 of in vitro procedures fail to implant

7
Embryo From the Third to the Eighth Week
  • First sign of human structure thin line down the
    middle (22 days) that becomes the neural tube,
    which eventually forms the central nervous
    system, including brain and spinal column
  • fourth week
  • head begins to take shape
  • heart begins with a miniscule blood vessel that
    begins to pulsate

8
Embryo From the Third to the Eighth Week, cont.
  • fifth week
  • arm and leg buds appear
  • tail-like appendage extends from the spine
  • eighth week
  • embryo weighs 1 gram and is 1 inch long
  • head more rounded face formed
  • all basic organs and body parts (but for sex)
    present
  • 20 of all embryos spontaneously abort now

9
Fetus From the Ninth Week Until Birth
  • Called a fetus from 9th week on

10
Third Month
  • Sex organs take shape (Y cell sends signal to
    male sex organs for females, no signal occurs)
  • genital organs fully shaped by 12th week
  • All body parts present
  • Fetus can move every part of body
  • Fetus weighs 3 ounces and is 3 inches long

11
Middle Three Months Preparing to Survive
  • Heartbeat stronger
  • Digestive and excretory systems develop more
    fully
  • Impressive brain growth (6X in size and
    responsive)
  • new neurons develop (neurogenesis)
  • synapsesconnections between neurons
    (synaptogenesis)

12
Middle Three Months Preparing to Survive, cont.
  • Age of viabilityage at which preterm baby can
    possibly survive (22 weeks)
  • 26 weeks survival rate about 50
  • brain maturation critical to viability
  • weight critical to viability
  • 28 weeks survival rate about 95

13
Fetal Brain Maturation
14
Final Three Months Viability to Full Term
  • Maturation of the respiratory and cardiovascular
    systems
  • critical difference
  • Gains weight4.5 lbs. in last 10 weeks

15
Risk Reduction
  • Despite complexity, most babies are born healthy
  • Most hazards are avoidable
  • Teratologystudy of birth defects
  • teratogensbroad range of substances that can
    cause environmental insults that may cause
    prenatal abnormalities or later learning abilities

16
Determining Risk
  • Risk analysisweighing of factors that affect
    likelihood of teratogen causing harm

17
Timing of Exposure
  • Critical periodin prenatal development, the time
    when a particular organ or other body part is
    most susceptible to teratogenic damage
  • entire embryonic period is critical

18
Amount of Exposure
  • Dose and/or frequency
  • Threshold effectteratogen relatively harmless
    until exposure reaches a certain level

19
Amount of Exposure, cont.
  • Interaction effectrisk of harm increases if
    exposure to teratogen occurs at the same time as
    exposure to another teratogen or risk

20
Genetic Vulnerability
  • Genetic susceptibilities product of genes
    combined with stress
  • Folic-acid deficiency may cause neural- tube
    defects
  • occurs most commonly in certain ethnic groups and
    less often in others
  • Males are more genetically vulnerable

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22
Specific Teratogens
  • No way to predict risk on an individual basis
  • Research has shown possible effects of most
    common and damaging teratogens
  • AIDS and alcohol extremely damaging
  • pregnant women with AIDS transmit it to their
    newborns high doses of alcohol cause FAS
    alcohol drug use increase risk to developing
    organism

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27
Low Birthweight
  • Low Birthweight (LBW)
  • less than 5 1/2 lbs.
  • grows too slowly or weighs less than normal
  • more common than 10 years ago
  • second most common cause of neonatal death
  • Preterm
  • birth occurs 3 or more weeks before standard 38
    weeks

28
Low Birthweight, cont.
  • Small for Gestational Age (SGA)
  • maternal illness
  • maternal behavior
  • cigarette smoking (25 of SGA births)
  • maternal malnutrition
  • poorly nourished before and during pregnancy
  • underweight, undereating, and smoking tend to
    occur together

29
Low Birthweight, cont.
  • Factors that affect normal prenatal growth
  • quality of medical care, education, social
    support, and cultural practices

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31
The Birth Process
  • Hormones in mothers brain signals process
  • Contractions begin strong and regular at 10
    minutes apart
  • average labor for first births is 8 hours

32
The Birth Process
33
The Newborns First Minutes
  • AssessmentApgar scale
  • five factors, 2 points each
  • heart rate
  • breathing
  • color
  • muscle tone
  • reflexes
  • score of 7 or better normal
  • score under 7 needs help breathing
  • score under 4 needs urgent critical care

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35
Variations
  • Parents Reaction
  • preparation for birth, physical and emotional
    support, position and size of fetus, and
    practices of mothers culture
  • Medical Attention
  • birth in every developed nation has medical
    attention
  • 22 of births in U.S. are cesarean section
  • removal of fetus via incisions in mothers
    abdomen and uterus
  • is medical intervention always necessary?

36
Birth Complications
  • Cerebral Palsybrain damage causing difficulties
    in muscle control, possibly affecting speech or
    other body movements
  • Anoxialack of oxygen that, if prolonged, can
    cause brain damage or death

37
First Intensive Care . . . Then Home
  • At the Hospital
  • many hospitals provide regular massage and
    soothing stimulation ideally, parents share in
    caregiving
  • At Home
  • complications, e.g., minor medical crises
  • cognitive difficulties may emerge, but high-risk
    infants can develop normally

38
Mothers, Fathers and a Good Start
  • Strong family support (familia)
  • Fathers play a crucial role
  • may help wives abstain from drugs or alcohol
  • can reduce maternal stress
  • Parental alliancecommitment by both parents to
    cooperate in raising child
  • helps alleviate postpartum depression

39
Mothers, Fathers and a Good Start, cont.
  • Parent-infant bondstrong, loving connection that
    forms as parents hold, examine, and feed their
    newborn
  • immediate contact not needed for this to occur
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