Chapter 4 Prenatal Development and Birth

Chapter 4- Prenatal Development Time of fastest development Conception –Ova (eggs) travels from ovary to uterus –Penetration by 1 of sperm –ZYGOTE (fertilized egg)

Prenatal Development and the Zygote

Menu 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: 3 rd to 8 th week (3 rd week - 2 nd month) –Organogenesis – every major organ takes shape –Sexual differentiation – begins during 7 th & 8 th 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: 9 th week – birth –Proliferation of neurons (250,000 per minute) – Migration of neurons –Differentiation of stem cells Age of viability – around weeks (fetus has possibility of surviving outside uterus) 3 rd 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

Menu LO 7.6 Germinal, embryonic, and fetal periods of pregnancy

Teratogens Thalidomide (for morning sickness) All or parts of limbs missing

Sudden Infant Death Syndrome

Fetal Alcohol Syndrome

“Copyright© Allyn & Bacon 2006” Low birth weight Developmental delay Epilepsy Poor coordination / fine motor skills Behavioral problems

2 six week old infants FAS Normal child

Teratogens - Diseases Rubella (German Measles) –Blind, deaf, heart, brain Syphilis:miscarriage, blind, deaf, heart, brain –After 18 th 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