Stages of Prenatal Development

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Stages of Prenatal Development

• Zygotic (germinal) stage
• Embryonic stage
• Fetal stage
• Critical period

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Critical Periods in Fetal Development
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PRENATAL DEVELOPMENT Critical
Periods
Week 3 Brain and spinal cord begin to form from neural tube
Weeks 3-4 Placenta and umbilical cord, eyes and primitive heartbeat
Week 5 Arms and leg buds
Week 8 Organogenesis complete now one inch long, weight 1/30th oz.
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Zygotic Stage

• Conception to 14 days
• Rapid Cell Division
• Process of Implantation

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Day One
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Implantation
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Embryonic Stage

• 2 weeks to 8 weeks
• Cell division
• Cell differentiation Embryogenesis
• Three layers of cell division
• endoderm
• mesoderm
• ectoderm

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Embryonic Stage

• Structures
• Amniotic sac
• Placenta
• Umbilical cord

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One Month
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Five Weeks
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Fetal Stage

• 8 weeks to birth
• 3rd month period of sexual emergence
• 5th month reflexes are present
• Zone of viability 24 weeks

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18 Weeks
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Four Months
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20 Weeks
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Fetal Stage

• Vernix
• Lanugo

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Fetal Behavior

• States of arousal
• Ability to learn