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Chapter 3

PSYB20Fall2013 Chapter 3.docx

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University of Toronto Scarborough
Diane Mangalindan

PSYB20Fall2013 Chapter 3: Prenatal Development and Birth STAGES OF PRENATAL DEVELOPMENT o egg lives about 3-5 days once released during ovulation o 3 periods during pregnancy, the period of the zygote, the embryo and the fetus The Zygote o First 2 weeks of life o Zygote  developing organism fom the time of the union of sperm + egg to about the second week of gestation; the period of the zygote is comprised of the implantation of the fertilized egg in the wall of the uterus o 1 o The Embryo o the developing organism between the 2 and 8 week of gestation o the period of the embryo comprises the differentiation of the major physiological structures and systems o gestation  carrying of an embryo or fetus during pregnancy, usually for 9 months in humans o from the time of fertilization to the end of the embryo phase the infant increases 2 million % in size o 3 crucial structures develop during this stage o amniotic sac  membrane containing a water fluid that encloses the developing organism, protecting it from physical shocks and temperature changes o placenta  fleshy, disc like structure formed by cells from the lining of the uterus and from the zygote, and that together with the umbilical cord serves to protect and sustain the life of the growing organism o umbilical cord  tube that contains blood vessels that carry blood back and forth between the growing organism and its mother by way of the placenta; carries Oxy and nutrients to the growin infant and removes carbon dioxide and waste products o inner mass differentiates into the ectoderm (skin, sensory cells, nervous system), mesoderm (mscle, skeleton, circulatory and excretory systems, inner skin layer), endoderm(GI tract, trachea and bronchia, glands and vital organs) o prenatal development is guided by 2 principles: cephalocaudal (development proceeds from head to tail) and proximal-distal (growth occurs first in central areas and then in more distant areas such as the arms and legs) o most miscarriages occur during this time, when the embryo becomes detached from the uterus wall and is expelled through vaginal canal  1 in 4 pregnancies but many go undetected because they occur very early in pregnancy, before the mother may even know she is pregnant The Fetus o developing organism from 3 month to the end o during fetal period, development of bodily structures and systems become complete o at the end of month 3, fetus has all of its body parts o at the end of month 4 mothers report movement o at around month 5 reflexes such as sucking, swallowing, and hiccupping usually appear o after 5 months the fetus develops nails and sweat glands, coarses skin and soft hair called lanugo which covers the body  lanugo may be shed before birth or after 2 o by month 6, eyes can open and close o if born at 6 months, babies cannot breathe adequately because they cannot produce and maintain enough surfactant  they develop respiratory distress syndrome (labored breathing, blue discoloration of the skin, often leads to death) o age of viability  22-26 weeks (5 ½ - 6 ½ months), by which point the fetus’ physical systems are well enough advanced that it has a chance at survival if born prematurely o babies born before 28 weeks can have many difficulties because the lungs and respiratory system continues to develop into the 9 month of pregnancy RISKS IN THE PRENATAL ENVIRONMENT o teratogens  environmental agent such as drug or medication that may cause developmental deviation in a growing human organism, most threatening in the embryonic stage but capable of causing abnormalities in the fetal stage as well o organism most vulnerable during embryonic stage o different teratogens influence different developmental processes o either maternal or fetal genotypes may counteract a teratogen’s effects o the effect of one teratogen may intensify effects of another  for example: nutritional deficiencies can intensify adverse effects of drugs that the mother has ingested o different teratogens may produce the same defect  example: deafness can be caused by ingesting quinine or streptomycin o the longer a fetus is exposed to a teratogen and the greater the effects, the more likely the fetus will be severely harmed Environmental Dangers LEGAL AND ILLEGAL DRUGS o 90% of women take some sort of drug during their pregnancy, usually because they do not yet know they are pregnant o even over the counter medicine can sometimes have negative effects on the developing zygote o example: heavy use of Aspirin has been associated with low bithwweight, lower IQ, and poor motor control NICOTINE AND ALCOHOL o over 30% of women smoke while pregnant, 17-25% of women drink while pregnant o smoking and drinkin is associated with changes in maternal physiology that leads to oxygen deprivation and this changes in the fetus’ brain o sudden infant death syndrome (SIDS) is more common in mothers that smoke, drink or take narcotic drugs  infants under the age of 6 months stop breathing and die for no apparent reason o even passive smoking (second hand smoking) can result in low birthweight o some studies show tat passive smoking can cause delays in intellectural and behavioral development and babies are more prone to becoming ill with pneumonia, bronchitis etc. o fetal alcohol syndrome (FAS)  a disorder echibited by infants of alcoholic mothers and characterized by stunted growth, a number of physical and physiological abnormalities and often mental retardation o fetal alcohol specturem disorder (FASD)  umbrella term used to describe the range of effects associated with prenantal exposure to alcohol o even moderate drinking by a preggo woman (like a glass of wine/day) can cause abnormal behavior pattern in her baby o children have problems paying attention, have lower IQ and in adolescence are at higher risk for alcohol problems and psychiatric disorders 3 HEROIN, COCAINE, AND OTHER DRUGS o offspring is also addicted to this substance and sustain toxic effect from these drugs o babies go through withdrawal  irritability, trembling, shrill crying, rapid respirations etc. o symptoms can be severed enough the infant dies within the first few days after being born o they do not display clinging, acting alert and maintaining eye contact which are the main behaviors by which infants initiate and sustain social interactions with their caregivers  may disrupt parenting and produce long term adverse outcomes in a parent-child realationship o study from Sick Children in TO  no difference in IQ between children who were exposed to cocaine prenatally and a group of control children, although cocaine-exposed kids scored lower on language tests o researcher suggested that the negative outcome sometimes observed in the cocaine exposed kids is due to other factors such as socio-economic status, low maternal education and other forms of maternal addiction o most studies have found few effects of prenatal marijuana exposure on fetal growth or on other physical growth postnatally o there have been some reports of cognitive impairment long lasting neurophysiological effects of prenantal marijuana exposure in 18-22 yr olds using fMRI techniques during a visuo-spatial memory task, although there did not appear to be any actual differeces in cognitive performance Environmental Toxins o radiation, lead, mercury, pesticides, herbicides, cleaners, food additives etc. o exposure to lead during pregnancy  prematurity and low birthweight, brain damage, physical defects and long term problems in cognitive and intellectual functioning o polychlorinated byphenyls (PCBs)  smaller babies, less responsible and less neurologically advanced than infants who had not been exposed to PCBs o long term effect from exposure to PCB  lower IQ, poorer memory, lower reading ability and higher levels of impusivity in 4 and 11 year old children o now banned, but Inuit ppl stil have high exposure, probably due to the amount of fish and marine life their mothers consume during pregnancy o men exposed to toxins can develop chromosomal abnormalities in their sperm which can result in miscarriage or breaing infants with birth defects Medical Interventions in Pregnancy and Childbirth SOME THERAPEUTIC DISASTERS o 1947-1964 diethylbestrol (DES) was prescribed to women to prevent them from miscarrying  discontinued when cancer and precancerous conditions were detected in the children of these women (both boys and girls were affected) o thalidomide  drug prescribed to relieve morning sickness but discontinued when ound to cause serious malformations in the fetus (currently may be used for AIDS, cancer and leprosy) MEDICATIONS USED IN LAB
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