Chapter 3 Notes
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This 2 page Bundle was uploaded by Kathryn Imming on Monday January 12, 2015. The Bundle belongs to CDE 232 at Arizona State University taught by Amy Reesing in Fall2014. Since its upload, it has received 179 views.
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Date Created: 01/12/15
Prenatal Development and Birth Chapter 3 The Course of Prenatal Development Conception to birth About 9 months or 38 weeks 2 ways of dividing up this period 0 3 trimesters Each trimester 3 months 0 3 periods Germinal Embryonic Fetal The Germinal Period First 2 weeks after conception rst 14 days Conception occurs in fallopian tubes Creation of the zygote through fertilization Cell division Differentiation of cells 0 Blastocyst inner layer of cells later becomes the embryo o Trophoblast outer layer of cells later provides nutrition and support for the embryo by becoming the placenta umbilical chord amnion Implantation of the organism in the uterine wall Embryonic Period From start of 3rd week through 8 weeks after conception Now called an Embryo Rate of cell differentiation intensi es Support systems formed Organs formed organogenesis Has all basic organs and body parts Weighs only 1 gram and is about an inch long Fetal Period Begins 2 months after conception and lasts on average about 7 months until birth Now called a fetus Growth and movement 0 Quickening Organs begin to function 0 Sex organs develop 0 Brain development is signi cant Age of viability is about 22 weeks after conception Teratogens Toxins illnesses and experiences can harm a developing person before birth Teratogens 0 Agents and conditions that can impair prenatal development and result in birth defects or death Birth defects include structural anomalies impaired learning or behavior Almost every fetus is exposed to a teratogen 0 But most exposure does not result in damage Effects of teratogens may not be immediate 0 Only about 12 of potential effects appear at birth Determining Risk Factors In uencing Severity amp Type of Birth Defect Type of teratogen Time of Exposure Critical Period more damage when they occur at some points in development rather than others Amount of Exposure Dose threshold effect often the greater the dose amp frequency the greater the effect Genetic Vulnerability based upon genotype of pregnant mother and genotype of the fetus Sensitivity to Teratogens During Germinal Period 0 Not susceptible to most teratogens 0 Could prevent implantation During Embryonic Period 0 Probability of structural defect is GREATEST During Fetal Period 0 Less likely to cause anatomical defects 0 More likely to stunt growth or create problems in organ functioning Fun Facts Approx 5 of babies are born on their speci c due date 50 are born within one week of the due date 90 are born within 2 weeks of the date
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