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Chapter 3

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University of Toronto Scarborough
Mark Schmuckler

Child Psychology 3 Canadian Edition Chapter 3 Prenatal Development and Birth Stages of Prenatal Development - Conception usually takes place during ovulation or within a few days of it - Pregnancy occurs in three trimesters; three periods of continuous development beginning with a zygote, which develops into an embryo, and then into a fetus - *Figure 3-1 o At almost 2 months, the embryo begins to look like a person - The Zygote o Period of the zygote is approximately the first two weeks of life egg is fertilized and implants in the wall of the uterus, tendrils from the zygote penetrate the blood vessels in the uterine wall and the zygote forms the physiological dependence on the mother that continues throughout the prenatal development - The Embryo o Second prenatal period begins after zygote has implanted in the uterus o Period of rapid growth from week 3-8; from the time of fertilization to the end of week 8, the infant has increased 2 million % in size o 3 crucial structures develop to protect and support the infant Amniotic sac thin membrane around organism that contains amniotic fluid fluid that embryo floats in and serves as protective buffer Placenta fleshy, disk-like structure formed from the tendrils that attach the embryo to the uterine wall Umbilical cord tube containing blood vessels, that joins the embryo to the placenta, carrying blood back and forth between the two o Semi-permeable membranes in the placenta, separating the bloodstreams of mother and child, allow some substances to pass from mother to child o Placenta and umbilical cord get oxygen and nutrients to the infant, and remove2CO and wastes o Developing organism differentiates into three layers Ectoderm from which hair, nails, parts of the teeth, outer skin layer, skin glands, sensory cells, nervous system develop Mesoderm forms muscles, skeleton, inner skin layer, circulatory and excretory systems Endoderm from which gastrointestinal tract, trachea, bronchia, Eustachian tubes, glands, and vital organs develop o Embryo is most susceptible during this period to environmental assault o Prenatal development is guided by Cephalocaudal principle development proceeds from the head downward to the trunk and legs Proximal-distal principle growth occurs from the central areas (internal organs) outwards (arms, legs) o Miscarriages, spontaneous abortions often occur in this period when, for some reason, the embryo becomes detached from the uterine wall and is expelled through the vaginal canal - The Fetus o Final period of prenatal development, from the beginning of the third month to delivery o Fetus experiences rapid growth in muscular development and the central nervous system o At 6 months, fetus cannot yet produce and maintain an adequate amount of surfactant which allows the lungs to transmit oxygen from air to the blood; i.e. without surfactant, infant will be unable to breathe adequately (if born prematurely)o Age of viability 22-26 weeks, physical systems are sufficient enough that the child has a reasonable probability of surviving if born premature, however some systems continue to develop into the ninth month Risks in the Prenatal Environment - Teratogens: environment agent that may cause developmental deviations in a growing human organism (i.e. drugs, pollution, mothers age, mothers diet) o Exert effects largely during critical periods; embryo is most vulnerable during the embryonic stage o Different ones influence different developmental processes o Maternal or fetal genotypes can counteract a teratogens effects o Effects of one teratogen may intensify the effects of another o Different teratogens may produce the same defect o The longer a fetus is exposed to a particular teratogen and the greater its intensity, the more likely it is that the fetus will be harmed - Environmental Dangers o Legal and Illegal Drugs some over-the-counter drugs, caffeine can have adverse effects on the fetus o Nicotine and Alcohol Smoking and drinking are related to disturbances in placental functioning and with changes in maternal physiology that lead to oxygen deprivation and therefore changes in the fetus brain Rate of miscarriages, prematurity, ndd low-birthweight babies is higher in mothers who smoke or drink, even 2 hand smoke can contribute Sudden infant death syndrome (SIDS) infants under 6 months old stop breathing and die without apparent cause more common in mothers who smoke, drink, or take narcotics Smokers babies are at
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