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CH.3 Prenatal Develop.docx

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Mark Schmuckler

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Twinkle Arora (PSYB20) CHAPTER 3: Prenatal Development and Birth Stages of Prenatal development - Conception takes place during a woman’s ovulation or within few days of it; the ovum or egg, once released from the mother ovaries lives about 3- 5 days - Prenatal development than encompasses the 38 weeks (9 months) b/w conception and birth - 3 stages (trinesters) – (1) Zygote (2) the embryo and (3) the fetus - Zygote – the developing organism from the time of the union of the sperm and the 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 - Once the zygote is implanted in the mother’s uterus the second prenatal period begins - Embryo - the developing organism b/w the second and eighth weeks of gestation the period of the embryo comprises the differentiation of the major physiological structures and systems - Gestation – the carrying of an embryo or fetus during pregnancy usually for nine months - During the embryo period – 3 curcial structures develop to protect and support the baby - 1. The amniotic sac 2. The placenta and 3. The umbilical cord - Amniotic sac - A membrane containing a watery fluid that encloses the developing organism, protecting it from physical shocks and temperature changes - Placenta – a fleshy, disk 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 - Umbilical cord - a tube that contains blood vessels that carry blood back and forth b/w the growing organism and its mother by way of the placenta; it carries O and nutr2ents to the growing infant and removes CO and wa2te products - The semi permeable membranes within the placenta separate the bloodstreams of the infant and mother - During the embryo period the inner mass of the developing infant differantes into 3 layers : the ectoderm, mesoderm and the endoderm - Ectoderm - the hair, nails and parts of teeth - Mesoderm – forms muscles, skeleton, circulatory and excretory system - Endoderm – froms the gastrointestinal tract, trachea, bronchia, and vital glands (lungs) - At the 4 week the neural folds (folds that form the CNS) being to close. If they fail to close the infant can develop spina bifida – disorder in the spinal cord - Prenatal development is guided by 2 principles = cephalocaudal and proximal distal - Cephalcaudal – the pattern of human physical growth in which development begins in the area of the brain and proceeds s downward to the trunk and legs - Proximal distal – wherein development starts in central areas such as internal organs and proceeds to more distant areas such as arms and legs - At 6 weeks the embryo is recognizable as a human being - Miscarriages – the natural end of pregnancy before the infant is capable of survival outside the womb and generally defined in humans as prior to 20 weeks of gestation (range – ¼ miscarriage) 1 Twinkle Arora (PSYB20) - The third and final period of prenatal development, the fetus – the developing organism from the 3 month of gestation through delivery; during fatal development of bodily structures and systems and becomes complete - At 3 months – the fetus has all its body parts - At 4moths – mothers usually report movement of the fetus - At 5 months – reflexes such as sucking, swallowing and hiccupping usually appear - Lanugo – a fine, soft hair that covers the fetus’s body from about the 5 month of gestation on; maybe shed before or after birth - at 6 months - eyes begin to open and close - if the infant is born prematurely at 6 months – the regulatory processes and nervous system and resspritiory systems are usually not mature enough for survival. At this time the fetus cannot produce and maintain an adequate amount of surfactant - surfactant - a liquid that allows lungs to transmit oxygen from the air to the blood - respiratory distress syndrome – a condition of the new born marked by laboured breathing and a blush discolouration of the skin or mucous membranes and which can often leads to death - age of viability – the age of 22 -26 weeks, by which point the fetus’s physical systems are well enough advanced that it has a chance at survival if born prematurely Risks in the prenatal development - teratogen – an environmental agent, such as drug, medication, dietary imbalance or polluting substance, they may cause developmental deviations in a growing human organism; most threatening in the embryonic stage but capable of causing abnormalities in the fatal stage aswell  a teratogen exerts its effects largely during critical periods  each teratogen exerts certain specific effects - different teratogens influence different developmental processes e.g. rubella (German Measles)  Either maternal or fetal genotypes may counteract a teratogen’s effects – abnormalities  The effects of one teratogen may intensify the effects of another  Different teratogens may produce the same defect  The longer a fetus is exposed ti a particular teratogen and the greater the intensity of the teratogen’s effects – the more likely it is that fetus will be seriously harmed Environmental Dangers - Heavy use of Asprin has been associated with low birth rate, lower IQ and poor motor control - Caffeine can too affect the developing fetus by increasing risks of a miscarriage - Smoking an d drinking are associated with disturbances in placental functioning and with changes in maternal physiology that lead to oxygen deprivation and thus changes in the brain - Sudden infant death syndrome (SIDS) – in which infants under the age of 6 months stop breathing and die w/o apparent cause, is more common in the offspring of mothers who drink or smoke - Prenatal nicotine exposure – poorer performance on measures of verbal comprehension 2 Twinkle Arora (PSYB20) - Passive smoking ( smoke breathed in by non-smokers ) – can contribute to low birth weight - Research has found – that if fathers smoked pregnancy their babies were 3 ounces lighter at birth than babies of non-smoking fathers - Babies exposed in utero to passive smoke are at increased risk for a variety of illnesses such as pneumonia, bronchitis , laryngitis and otisis media (ear infection) - Fetal Alcohol syndrome (FAS) previously known as “Mother’s ruin” – a disorder exhibited by infants of alcoholic mothers and characterised by stunted growth, a # of physical and physiological abnormalities and often mental retardation - Withdrawal symptoms – refers to a group of symptoms that may occur from suddenly stopping the use of alcohol after chronic or prolonged ingestion - Symptoms can be severe enough to result in an infant’s death in the first few days of life - Cocaine effects – physical defects – including bone, genital, urinary tract, kidney, eye and heart deformities and brain haemorrhages - Dangerous substances in the everyday environment are also harmful to children – radiation, lead, mercury, herbicides, pesticides, etc - Polychlorinated biphenyls (PCB’s) – which were used routinely in e
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