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PSY2105 (102)
Chapter 4

Chapter 4.docx

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University of Ottawa
David Collins

Chapter 4 Stages of Prenatal Development ­ Conception: fertilization of the egg by the sperm o Forms a single cell called the zygote ­ Period of the zygote: conception to the second week o Implantation takes a week ­ Period of the embryo: third to eighth week o the developing organism when implantation is complete o Major structures start to form  Endodermal layer: develop into internal organs  Ectodermal layer: part that has contact with the world  Mesodermal layer: muscles, bones, sex organs, heart o Prenatal development: 3 major structures form by the end of this period  Amniotic sac: watertight membrane fluid that forms outside the embryo maintaining a constant temperature for the embryo.  Placenta: organ through which mother and embryo exchange materials.  Umbilical cord: connects embryo to placenta. It transports oxygen and nutrients from placenta to fetus and waste products from fetus to placenta. There are no pain receptors  1 month (at the end of 4 weeks): • baby is ¼ long • heart, digestive system, backbone and spinal cord begins to form • placenta develops  2 months (end of 8 weeks) • baby is 1 – 1/8 long • heart is functioning • facial features forming • penis appears in boys • baby can move, but the mother does not feel it  3 months (end of 12 weeks) • develops nails and earlobes • has most organs and tissues • brain has organized into functional units • fetal activity begins  4 months • foundation of all organ systems are formed and fetal development becomes primarily growth  Toward independence • Age of viability: age when the infant has the chance to live if born prematurely • Problems: o Not able to use lungs o Cannot digest food or control temperature because fat has not been formed • only during 9 months does the baby receive antibodies from its mother to prevent infections Birth Weight ­ low birth weight (LBW) is not always associated with premature birth ­ premature and small full-term infants have very different problems ­ Suppose a LBW… o If born full term  LBW indicates Small for gestational age o If born pre term  Baby could beAGA or SGA ­ Small for gestational age o Effects on development:  Physical growth: retardation from inadequate nutrition in the utero  Mental retardation (poor brain development)  More problems later in life ­ Appropriate for gestational age o Low risk if preterm o Developmental delay before 1 year ­ Large for gestational age o Birth injuries  Fracture of the clavicle  Brachial plexus injury o Developmental difficulties  Respiratory distress syndrome  Developmental retardation Teratology ­ teratogen: agent that can cause abnormal development in the fetus. It can have physical or psychological effects ­ teratology: study of the effects of teratogen on development ­ General principles: how teratogens act: o Its effect depends on the genetic makeup of the organism exposed to it.  Ex. Thalidomide. Did not affect animals but did humans o Its effect on development depends on timing  Especially between 2 – 8 weeks because organs are forming o Effect of teratogen may be unique o Abnormal development caused by teratogens can be severe o They differ in how they gain access to the fetus o Teratogen dosage is related to degree of abnormal development ­ Types of teratogens o Drugs: any substance other than food intended to affect the body  Thalidomide: • Sold as a non-addictive sleep aid • Helps reduce morning sickness • Depending on when taken, it can cause malfunction to body parts, and causes phocomelia: limbs are shortened and hands and feet are connected to the torso  other therapeutic drugs • drugs could interact with other substances and cause teratogens • some sex hormones could produce teratogens  Street drugs • Heroine o Compounded by poor nutrition and inadequate health care o Women are more likely to miscarry or have a premature child o Babies are born lighter than usual o Can use methadone to help break the habit • Cocaine o Affects the fetus (limiting its supply of oxygen and nutrients) o Cocaine affect the nerve transmitters in the brain o Babies are likely to be miscarried or still born • Marijuana o Causes babies to be jittery and have poor vision o THC can cross placenta and build up in the fetus o The effects on the embryo or fetus are uncertain • Caffeine o Associated with increased risk of premature birth and lower birth weight babies • Nicotine o Smoking is known to impair functioning of the placenta o Babies are smaller and have a higher risk for social and behavioral problems o Poor cognitive development o Prenatal complications  Growth retardation  Miscarriage  Still birth o Postnatal complications  LBW  SIDS  Cognitive and social issues  Growth retardation • Alcohol o Babies suffer from mental retardation o Fetal alcohol syndrome (FAS): problems with the child given from the mother who consumes alcohol.  Neurological abnormalities • Developmental delays • Behavioral dysfunction (ADHD) • Intellectual impairment • Skull or brain malformations  Characteri
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