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Chapter 3


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Konstantine Zakzanis

CH3 Identify and describe the major events of the three periods of prenatal development  The zygote: o The first 2 weeks of life, a sperm fertilizes the ovum (zygote/ fertilized egg)proceeds down the mother’s fallopian tube and implants in the wall of the uterus7 days after, tendrils from the zygote penetrate blood vessels in the wall of the uterus (the zygote forms the physiological dependence with the mother  Embryo: o From 3 week of gestation (the carrying of an embryo/fetus during pregnancy, usually for nine months in humans) to 8 week o Amniotic sac: a thin membrane around the developing organism (contain amniotic fluid)allow embryo floats, serves as a protective buffer against physical shocks and temperature changes o Placenta: the tendrils that attach the embryo to the uterine will increase in size and complexity to form a fleshy disc-like structure o Umbilical cord: tube that contains the blood vessels that carry blood back and forth btw the infant and placenta: o Semi-permeable membranes with the placenta separate the bloodstreams of the mother and child: transmit oxygen and nutrients to the infant and remove carbon dioxide and waste products from it o Ectoderm: the hair, nails, parts of teeth, the outer layer of the skin glands, and the sensory cells and the nervous systems develop o Mesoderm: forms into muscles, skeleton, circulatory and excretory systems and inner skin layer o Endoderm: the gastrointestinal tract, trachea, bronchia, Eustachian tubes, glands, and vital organs (lungs, pancreas, liver) o Prenatal development is guided by Cephalocaudal (from head to legs), proximal-distal (from center to more distant areas) o Most miscarriages/ spontaneous abortions occur during this period  Fetus: o From the beginning of third month of gestation to delivery o Rapid growth in muscular development and the central nervous system o At the end of the third month, fetus has all its body parts o By the end of the forth month, the fetus develop nails and sweat glands, coarser, more adult-like skin and lanugo (soft hair – cover the body) o By 6 month, it can open its eyes o If the infant born prematurely at 6 month, the regulatory processes and nervous and respiratory systems are usually not mature enough for survival without intensive interventionX produce and maintain an adequate amount of surfactant (a liquid that allows the lungs to transmit oxygen from the air to the bloodwithout surfactant, infant are unable to breatherespiratory distress syndrome (a condition of the newborn marked by labored breathing and a blush discoloration of the skin/ mucous membranes)flaring nostrils, a grunt-like sound on expiration o Age of viability: 22-26 weekshas advanced physical systemborn prematurelyhas reasonable probability of surviving 6 principles describe the effects of teratogens on prenatal development (EG.)  Teratogens: an environmental agent (drug, medication, dietary imbalance, polluting substance) that may cause developmental deviations in a growing human organism; most threatening in the embryonic stage but capable of causing abnormalities in the fetal stage as well 1. A teratogen exerts 運用 its effects largely during critical periods  During embryonic stagethe most vulnerable to teratogen  Each organ system has a different critical period (EG. The heart – 20~40 days of life) 2. Each teratogen exerts certain specific effects  Different teratogens influence different developmental processes  EG. Rubella/ German measles in mother’saffect fetus eyes, heart and brain/ the drug thalidomide causes primarily malfunctions of the limbs 3. Either maternal/ fetal genotypes may counteract a teratogen’s effects  EG. Not all pregnant women who have German measles have defective infants 4. The effects of one teratogen may intensify the effects of another  The mothers physiological status, nutrition, and hormonal balance modify the impact of a teratogen  EG. Nutritional deficiencies (interfere with healthy prenatal development)also intensify adverse effects of drugs that the mother has ingested 5. Different teratogens may produce the same defect  EG. Deafness may result if the mother contracts rubella/ if she ingests quinine/ streptomycin 6. The longer a fetus is exposed to a particular teratogen and the greater the intensity of the teratogen’s effects, the more likely it is that the fetus will be seriously harmed  The does-response principle: the higher the does, the more severe the damage to the developing fetus The influence of alcohol exposure on prenatal development (fetal alcohol syndrome, fetal alcohol effects)  Smoking and drinking are associated with disturbances in placental functioning and with changes in maternal physiology that lead to oxygen deprivation to changes in the fetus’s brainmiscarriages, prematurity, low-birthweight babies  Sudden infant death syndrome (SIDS): infants under the age of 6 months stop breathing and die without apparent cause  Prenatal nicotinecognitive effect  Maternal smokingpoor performance on measures of verbal comprehension and fine motor skill at 13 months; poor language development at 3-4; problems in visual and auditory attention btw 4-7; visuoperceptual functioning problems btw 9-12; intellectual, attention, memory problems in adolescents  Passive smokelow birthweight; cause delays in intellectual and behavioral development; high risk in pneumonia, bronchitis, laryngitis, otitis media, and inner-ear infection  Fetal alcohol syndrome (FAS): high incidence of facial, heart, limb defects o 20% shorter than the average child of their age and are often mentally retarded  Fetal alcohol spectrum disorder (FASD): describe the range of effects associated with prenatal exposure to alcohol  Symptoms: excessively irritable, distractible, hyperactive and may engage in such behaviors as repeatedly banging their heads/ rhythmically rocking their bodies; exhibit failure to become accustomed to repeated stimuli; slow/unable to learn to performs action as turning their heads/ sucking; having trouble to pay attentiondo poor in school, low score in IQ test  In young adulthood – higher risk for alcohol problems and psychiatric disorder  Prevention: o Increase public awareness of the potential risks of drinking during pregnancy (publication of joint guidelines by Canadian Centre on Substance Abuse; Addition Research Foundation in 1993… o Televised public awareness campaigns (Manitoba); the inclusion of warning labels on containers of alcoholic beverages/ warning signs put up in places selling alcohol The most common prenatal influences on development; the effects of maternal diet, emotional state, age (EG.)  Heroin, Morphine, Cocaineirritability, minimal ability to regulate their state of arousal, trembling, shrill crying, rapid respiration, hyperactivity  These infant are often premature and low of birth weightdifficult to cope with trauma of withdrawal symptoms  The severity of symptoms is related to the length, continuity, and intensity of mother’s addition (EG. If the mother stop s taking drugs in the third trimester, the infant is less likely to be affected)  The babies don’t cling and cuddle, they don’t become alert as normal babies  Physical defects: bones, genital, urinary tract, kidney, eye, heart deformities, brain hemorrhages  Sustained attention, impulsive, highly distractible, difficult to control  Environmental toxin: radiation, lead, mercury, herbicides, pesticides, pesticides, household cleaners, food additives and cosmetic o Lead- caused by inadvertently inhaling automobile exhaust, drinking water contaminated by industrial waste/ living in an environment painted with lead-based paintbrain damage, physical defects, long-term problems in cognitive and intellectual functioning o Polychlorinated biphenyls (PCBs): used routinely in electrical transformers and capacitatorsbabies were smaller, less responsive, less neurologically advanced than infants who had not been exposed to PCBslong-term effect: lower IQ, poorer memory, lower reading ability, higher levels of impulsivity in 4, 11 o Affect father’s sperm; through breast feeding o Chromosomal abnormalityaffect fertility; increase risk of miscarrying/ bearing infants with birth defects  Diethylstilbestrol (DES): help to prevent pregnant woman from miscarrying o (babies)Vaginal abnormalities, cancer of the cervix in adolescence o (young women) high rate of problems in pregnancy, spontaneous abortions, premature delivery, babies with low birth weight o (sons) damage of reproductive tract – EG. seminal fluid abnormalities  Thalidomide: an anti-anxiety and anti-nausea drugrelieve symptoms of morning sickness o Cause deformations of the eyes, nose, and ears; cleft palate; facial palsy; fusing of fingers and toes; dislocations of the hip joint and malformations of the heart and the digestive and genito-urinary tract; phocomelia: limbs are missing and the feet and hands are attached directly to the torso – look like flippers  It’s difficult when the abnormalities appear for doctor to figure out that these drugs causing birth defects because the pregnant women themselves showed no adverse effects from the drug  Maternal ingestion of reserpine, a tranquillizer may lead to respiratory problems in an infant o Tranquilizer may depress infant skeletal growth o Anti-convulsant drugscleft lip and palatal, heart and skeletal defects  Anesthetics (epidural, spinal block, general as aesthetics)ease the pain during birth o Affect on babies: less responsiveness less smiling, more irritability for several days after days, depression, motoric disorganization, disruptions in feeding responses, also impaired attention and motor abilities at 1month of age, usually no longer o Depend on genetic factors, mother’s health, the length of labor, the size of the baby, the mother’s attitude Mental factors:  Age and parity (how many children she has already borne) o Women who have the first child when they are under 15/over35 are likely to experience more problems during pregnancy, complications during delivery o Older women are more difficulty conceiving a childthe chance of becoming pregnant declines steadily after 27 and by 40, it’s less than 5% o The incidence of born miscarriage and chromosomal abnormality increase with the age if the mother and her reproductive system o Men don’t become less fertile as the age but tend to have more infants with birth defects due to deteriorating quality of sperm in old
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