Human Growth and Development

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Human Growth and Development

• Chapter Four Prenatal Development and Birth

PowerPoints prepared by Cathie Robertson,
Grossmont College Revised by Jenni Fauchier,
Metropolitan Community College
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From Zygote to Newborn

• Germinal periodfirst 14 days
• Embryonic period3rd through 8th weeks
• Fetal period9th week through birth

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Process of Conception
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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

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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

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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

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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

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Fetus From the Ninth Week Until Birth

• Called a fetus from 9th week on

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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

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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)

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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

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Fetal Brain Maturation
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Final Three Months Viability to Full Term

• Maturation of the respiratory and cardiovascular
  systems
• critical difference
• Gains weight4.5 lbs. in last 10 weeks

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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

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Determining Risk

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

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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

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Amount of Exposure

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

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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

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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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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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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

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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

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Low Birthweight, cont.

• Factors that affect normal prenatal growth
• quality of medical care, education, social
  support, and cultural practices

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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

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The Birth Process
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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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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?

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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

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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

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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

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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