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Chapter 4 Prenatal Development and Birth

Chapter 4 Prenatal Development and Birth. Chapter 4- Prenatal Development. Time of fastest development in life span Environment extremely important Conception Ova (eggs) travels from ovary to uterus Penetration by 1 of 300-500 sperm Outcome: single-celled ZYGOTE (fertilized egg).

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Chapter 4 Prenatal Development and Birth

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  1. Chapter 4Prenatal Development and Birth

  2. Chapter 4- Prenatal Development • Time of fastest development in life span • Environment extremely important • Conception • Ova (eggs) travels from ovary to uterus • Penetration by 1 of 300-500 sperm • Outcome: single-celled ZYGOTE (fertilized egg)

  3. Prenatal Development and the Zygote

  4. 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: 15% (recognized) to 50% • Embryonic period: 3rd to 8th week (3rd week - 2nd month) • Organogenesis – every major organ takes shape • Sexual differentiation – begins during 7th & 8th week (sex genes impact formation of testes or ovaries)

  5. Outer Layer of Blastocyst (150 cells) forms: • Amnion – a watertight membrane that fills with fluid that cushions and protects the embryo • Chorion – a membrane that surrounds the amnion and attaches rootlike extensions called villi to the uterine lining to gather nourishment for the embryo. The chorion eventually becomes the lining of the placenta • Placenta – tissue fed by mother’s blood vessels and connected to the embryo by the umbilical cord • Umbilical cord – connection between embryo and mother through which nutrients and wastes are exchanged • Placental barrier – protects developing child from many harmful substances, and allows small molecules exchanged between mother and embryo

  6. Inner cell mass of blastocyst forms: • Ectoderm – eventually forms the central nervous system (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

  7. Figure 4.3

  8. Fetal period: 9th week – birth • Proliferation of neurons (250,000 per minute) • Migration of neurons • Differentiation of stem cells • Ends in tremendous brain development Age of viability – around 24-25 weeks (fetus has possibility of surviving outside uterus) 3rd Trimester – myelination (insulating cover that increases speed of transmission)

  9. Prenatal Development and the Newborn 40 days 45 days 2 months 4 months

  10. Prenatal Environment • Reciprocal influence • Person and environment • Good and bad influences important • Teratogen: harmful environmental agent • Harms the developing fetus • Critical Period: Organogenesis • Dosage & duration • Genetic make-up: susceptibility

  11. Teratogens-Drugs • Thalidomide (for morning sickness) • All or parts of limbs missing • Tobacco: miscarriage, low birth weight, SIDS, slows fetal growth • Alcohol: FAS • Small, facial deformities, retardation • Cocaine: Processing difficulties

  12. Figure 4.6

  13. FETAL ALCOHOL SYNDROME

  14. 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

  15. 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 – brain cells die – can cause mental retardation or cerebral palsy (difficulty controlling muscle movements and possibility of MR)

  16. 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

  17. APGAR TEST • Provides a quick assessment of the newborn’s: • Heart rate (0-2 points) • Respiratory effort (0-2 points) • Muscle tone (0-2 points) • Color (0-2 points) • 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

  18. 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 • Parenting must be attentive, responsive

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