Human Growth and Development

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Human Growth and Development Chapter
Four Prenatal Development and Birth
Agenda Finish Lecture1-3 (and 2
activities) Discuss XC observation Quiz 1-3
due Lecture Chapter 4 with video clips (sonogram,
preemie, birth)
Everyone needs to be valued. Everyone has the
potential to give something back. Princess
Diana
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• Germinal periodfirst 14 days
• Embryonic period3rd through 8th weeks
• Fetal period9th week through birth

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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

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• 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 outer cells is to achieve
  implantation
• 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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• 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
• -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 develop
  (synaptogenesis)

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• 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
• Gains weight4.5 lbs. in last 10 weeks

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• Teratologystudy of birth defects
• teratogenssubstances that may cause prenatal
  abnormalities or later learning disabilities

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Timing of exposure is important

• 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 is important

• Dose and/or frequency
• Threshold effectamount when dangerous
• Interaction effectother teratogens also present

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Genetic Vulnerability

• Males are more genetically vulnerable

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Specific Teratogens

• No way to predict risk on an individual basis
• 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 Birth Weight

• Low Birth Weight (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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• Small for Gestational Age (SGA)
• maternal illness
• maternal behavior
• cigarette smoking (25 of SGA births)
• maternal malnutrition
• poorly nourished before and during pregnancy
• underweight, under-eating, and smoking tend to
  occur together

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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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Birth Complications

• Anoxialack of oxygen that, if prolonged, can
  cause brain damage or death

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Mothers, Fathers and a Good Start

• Strong family support
• Fathers play a crucial role
• Parental alliancecommitment by both parents to
  cooperate in raising child
• helps alleviate postpartum depression

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• Parent-infant bondstrong, loving connection that
  forms as parents hold, examine, and feed their
  newborn