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Chapter 4

Chapter 4 - Prenatal Development.docx

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David Collins

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PSY 2105 FChapter 4 Prenatal Development thSeptember 26 2012 Stages of Prenatal DevelopmentConception o Fertilization of the egg by the spermformation of zygote 24 hour window Period of the zygote conception to the second week o implantation in uterus lining at 1 week o prenatal development already underway by the time a woman suspects she may be pregnantPeriod of the embryo o The third to the eighth week6 weekMajor internal and external structures formMost delicate period vulnerableStages of Prenatal GrowthEmbryonic Period 38 weeks o Embryo forms different layers of cellsEctodermoutside layer becomes nervous system sensory receptors and skinMesoderm Middle layer becomes circulatory system heart begins to beat at 4 weeks muscles bones excretory system and reproductive system EndodermInner layer becomes digestive system and respiratory systemo Development of other prenatal essentials PlacentaWhere blood vessels of mother and child intertwineOrgan that allows mom and baby to interactUmbilical CordConnects embryo to placentaAmnionClear fluid sack that protects embryo Umbilical CordConnecting link between fetus and placenta o Transports oxygen and nutrients to fetus from the placenta and returns waste products from the fetus to the placenta o Contains NO pain receptors 1PSY 2105 FChapter 4 Common LanguageTRIMESTERSTrimester 1stweeks 113 LMP 2stweeks 1426 3stweeks 27 and on full term is 3840 weeks 1 MonthFirst Trimester At the end of four weeks Baby is 14 inch in length Heart digestive system backbone and spinal cord begin to form Placenta begins to develop The single fertilized egg is now 10000 times larger than size at conception Month 2First Trimester At the end of 8 weeks Baby is 118 inches long Heart is functioning Eyes nose lips tongue ears and teeth are forming Penis begins to appear in boys Baby is moving although the mother cannot yet feel movementMonth 3 First Trimester At the end of 12 weeks Baby is 2 12 to 3 inches long Weight is about 12 to 1 ounce Baby develops recognizable formo Nails start to develop and earlobes are formed Arms hands fingers legs feet and toes are fully formed Eyes are almost fully developed Baby has developed most of hisher organs and tissues Babys heart rate can be heard at 10 weeks with a special2
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