chapter 4 prenatal development and birth. chapter 4- prenatal development time of fastest...
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Chapter 4Prenatal Development and Birth
Chapter 4- Prenatal Development
• Time of fastest development
• Conception– Ova (eggs) travels from ovary to uterus– Penetration by 1 of 300-500 sperm– ZYGOTE (fertilized egg)
Prenatal Development and the Zygote
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LO 7.6 Germinal, embryonic, and fetal periods of pregnancy
Prenatal Stages• Germinal period: days 1-14 (0 - 2 weeks)
– Zygote’s implantation into uterine wall: 1/2 are successful
– Zygote divides many times through mitosis to form blastocyst (about 150 cells)
– Miscarriage: 8-30% (recognized) to 33% (unrecognized)
• Embryonic period: 3rd to 8th week (3rd week - 2nd month)– Organogenesis – every major organ takes shape– Sexual differentiation – begins during 7th & 8th week
Outer Layer of Blastocyst (150 cells) forms:
• Amnion – a watertight membrane that fills with fluid that protects the embryo
• Placenta – provides nourishment by mother’s blood vessels
• Umbilical cord – connection between embryo and mother
• Placental barrier – protects developing child from many harmful substances, and allows small molecules exchanged
Inner cell mass of blastocyst forms:
• Ectoderm – (brain and spinal cord)• Mesoderm – muscle tissue, cartilage, bone,
heart, arteries, kidneys, and gonads• Endoderm – gastrointestinal tract, lungs, and
bladder
Neural plate forms neural tube (bottom is spinal cord)
Top of tube forms into forebrain, midbrain, hindbrain
Figure 4.3
• Fetal period: 9th week – birth– Proliferation of neurons (250,000 per minute)– Migration of neurons – Differentiation of stem cells
Age of viability – around 23-25 weeks (fetus has possibility of surviving outside uterus)
3rd Trimester – myelination
Prenatal Development and the Newborn
40 days 45 days 2 months 4 months
Prenatal Environment
• Teratogen: harmful environmental agent–Harms the developing fetus–Critical Period: Organogenesis–Dosage & duration–Genetic make-up: susceptibility
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LO 7.6 Germinal, embryonic, and fetal periods of pregnancy
TeratogensThalidomide (for morning sickness)
All or parts of limbs missing
• Sudden Infant Death Syndrome
Fetal Alcohol Syndrome
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Fetal Alcohol Syndrome.• Low birth weight • Developmental delay• Epilepsy• Poor coordination / fine
motor skills • Behavioral problems
Teratogens - Diseases
• Rubella (German Measles)– Blind, deaf, heart, brain
• Syphilis:miscarriage, blind, deaf, heart, brain– After 18th week
• AIDS mothers transmit to babies (15%-35%)– Prenatally, perinatally, postnatally
Teratogens – Environmental Hazards
• Radiation: MR, leukemia, cancer, mutations, spontaneous abortions, etc.– Avoid X-rays when pregnant
• Pollutants– In air and water– Lead - MR (also postnatally)
Anoxia – Oxygen shortage –can cause mental retardation or cerebral palsy
Postnatal Depression
• Baby Blues, mild, common
• Postpartum depression: 1/10– Previous depression common
• Children of depressed mothers – Insecurely attached, less responsive– Negative to other children
APGAR TEST
• Provides a quick assessment of the newborn’s:
1)Heart rate (0-2 points)
2)Respiratory effort (0-2 points)
3)Muscle tone (0-2 points)
4)Color (0-2 points)
5)Reflex irritability (0-2 points)
The Apgar test is given immediately and 5 minutes after birth
7 or higher = good shape
4 or lower = at risk
The Neonatal Environment
• Culture, early socialization, health status– E.g., low birth-weight babies (8% in US)
• Less than 5 1/2 lbs or 2500 grams•Strongly linked to low SES•Environment: neonatal intensive care•Risk: blindness, deafness, CP, autism,
cognitive, and later academic problems