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Chapter 4

304- Chapter 4 summary.rtf

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PSYC 304
Kristine Onishi

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psyc-304 Chapter 4: Prenatal Development, Birth, and Newborns' Readiness for life Just b/c risk is associated with a certain behviaor does not mean that engaging in the bhevaior will ensure that outcome. All sexuality active men and women should be aware of the possibility of a preganancy, the critical period of early weeks of pregnancy, and the wisdom of adjusting their lifestyles to provide a healthy prenatal environment. From conception to birth From moment of conception, it will take around 266 days for the one-celled zygote to go through 3 major phases, andbecome foetus of some 200 billion cells ready to be born. The period of the Zygote (1st phase) From conception through implantations when the zygote becomes attached to uterus lining and lasts about 10-14 days. As it moves down the fallopian tubes, it undergoes mitosis into 2 cells, then a blastocyst that will contain 60 to 80 cells within 4 days of conception. Its inner layer will become the embryo, while the outer layer will develop into tissues that protect and nourish the embryo • Implantation: occurs when a blastocysts approaches the uterus and attaches in uterine wall. There is a specific window of implantation during which the blastocyst must communicate biologically with the uterine wall, position itself, attach and invade. It occurs about 7 to 10 days after ovulation and lasts about 48 hours. Only about half of all fertilized ova are firmly implanted, and all others are either genetically abnormal and fail to develop, or burrow into a site incapable of sustaining them and are miscarried. Nearly 3 zygote out of 4 fail to survive the initial phase. • Development of Support sytems: Outer layer of blastocyst rapidly forms 4 major structures to protect and nourish the developping organism. (1) amnion: watertight sac that fills with fluid from the mother's tissues. this sac and the amniotic fluid cushion the developping organism against blows, regulate its temperature, and provde weightless environment that will make it easier for embryo to move. Floting in this environment is a ballon shaped yolk-sac . (2) yolk-sac: that produces blood cells until embryo is capable of producing its own and is attached to 3rd membrane. (3)Chorion: surrounds the amnion and will become linig of placenta (4) Allantois: form the embryo's umbilical cord. • Purpose of Placenta: placenta is fed by blood vessels from the mother and the embryo. Acts as barrier preventing both bloods to mix. Is semipermeable allowing only certain substances to pass such as gases (Oxygen), salts, and nutrients AND delivers it to the embryo. It also transports metabolic wastes and carbon monoxide from embryo. PLays a crucial role in prenatal development The period of the embryo (2nd phase) From beginning of 3rd week through end of 8th week. Period where all major organs are formed and the heart starts beating. By 3rd week: embryonic disk is rapidly differentiating into 3 cell layers: (1) Ectoderm (outer layer) will become nervous system, skin and hair. A portion of it will fold into a neural tube that will become brain and spinal cord. (2) Mesoderm (middle layer) will become muscles, bones and circulatory system (3) Endoderm (inner layer) will become digestive system, lungs, urinary tract, and other vital organs such as pancreas and liver. By end of 4th week, heart has started to beat. Embryo is about 0.6cm. • The second month: embryo becomes more human in appearance as it grows 1mm per day. A primitive tail grows and will become the coccyx. By middle of 5th week, the eyes have corneas and lenses. By 7th week, ears are well formed and embryo has rudimentary skeleton. Limbs are developing from body outward; upper arms appear, then forearms, hands and fingers. Brain develops rapidly during second month as it directs organism's frist muscular contractions by the end of embryonic period. During 7th-8th week, embryo's sexual development beings with appearance of genital ridge called indifferent gonad. If it is a male, a gene on Y chromosome will trigger a biochemical reaction that instructs the indifferent gonad to produce testes. If it is a female, then X chromosome will trigger the production of ovaries. Embryo's circulatory system functions on its own. Embryo is slightly more than 2.5 cm long and weight less than 7.0 g. The period of the fetus (3rd phase) From 9th week of pregnancy until the baby is born. All major organs begin to function, and developing organisms grows rapidly. Fetus begins to move, sense and behave. Individuality emerges as different fetuses develop unique characteristics such as different patterns of movement and different facial expressions. • The third month: Organ systems that were formed earlie continue their rapid growth and become interconnected. Coordination between nervous system and muscular systems allow the fetus to perform many interesting manoeuvres (ie. kicking its legs) but still too subtle to be felt by pregnant woman. The digestive and excretory systems are also working together. Sexual differentiation is rapidly progressing. Male testes secrete testosterone and develop penis and scrotum. In absence of it, female genitalia form. By end of 3rd month, sex of fetus can be detected by ultrasound and its reproductive system already contrains immature ova or sperm cells. Already there after 12 weeks when fetus is 7.5cm and weights less than 28g. • The second Trimester: the fourth through sixth months: Development occurs at rapid pace during 13th through 24th weeks of pregnancy. At 16 weeks, fetus is about 20-25cm long and weight about 170g. From 15-25 weeks, simple movements of the tongue, lips, pharynx, and larynx increase in complexity and coordination, so fetus begins to suck, swallow, munch, hiccup, coudh and snort; preparing for extra-uterine life. Fetus begins to kick strong enough to be felt by pregnant woman. Fetal heartbeat can be easily heard with stethoscope, and as amount of bone and cartilage increases, the hardening skeleton can be detected by ultrasound. By end of 16th week, fetus has assumed a distinctly human apperance, but no chance of survival outside of womb. During 5th-6th months, nails haren, skin thickens, and eyebrows, eyelashes aand scalp hair appear. At 20 weeks, sweat glands are functionning and fetal heartbeat is often strong enough to be heard by placing ear on abdomen. Fetus is covered by white cheesy substance called vernix (protecrs fetal skin against chapping druing long exposure to amniotic fluid) and fine layer of body hair called lanugo (helps vernix stick to skin). By end of 6th month, fetus's visual and auditory sense are clearly functional. (preterm babies born at 25 weeks become alert at sound of loud bell and blink in response to light). Use of magnetoencephalography (MEG) has revealed that the fetus has some ability to discriminate between sounds. May indicate presence of a rudimentary, fetal short-term memory system. Fetus is about 35-38cm and weight under 1kg. • The third Trimester: the seventh through ninth months: All organ systems mature rapdily, preparing fetus for birth. Between 22-28 weeks, fetuses reach the age of viability. Fetal monitoring techniques revealed that 28- to 32- week-old fetuses begin to show better organized and more predictable cycles of heart rate activity, gross motor activity, and sleepiness/waking activity, findings that seem to indicate that their developping nervous systems are now sufficiently well organized to allow them to survive if premature birth occurs. However, fetuses born at this stage still require oxygen assitance b/c pulmonary alveoli in their lungs are too immature to inflate and exchange gases on their on. By end of 7th month, fetus weight over 1,8 kg and is about 40-43 cm long. By 8th month, it is about 46cm and put on another 0.5-1 kg; much of this fat comes from fat deposited under skin that will help insulate baby to changes of temperature. By middle of 9th month, fetal activity slows and sleep increases. Fetus starts to position in fetal position, and near cervix. Over the last month, the uterus contracts, cervix dilates and prepares to give birth. Environmental Influences on Prenatal Development Teratogens The term refers to any disease, drug or other environmental agent that can harm a developping embryo or fetus by causing physical deformities, severely retarded growth, blindness, brain damage, and even death. About 95% of newborns babies are perfectly normal and that many those born with defects have mild, temporary or reversible problems. Effects of a teratogen on a body part or organ system are worst during period when that structure is forming and growing most rapidly. Genetic makeup influences the susceptibility of being affected by a teratogen. Same defect can be cause by many teratogens; and a variety of defects can be cause by same teratogen. The longer the exposure (or higher dose); the more serious harm can be caused. Embryos and fetus can be harmed by fathers' as well exposure too. The long term effect can depend on the quality of postnatal environment. Some teratogen cause "sleeper effects" that may appear later in life. Each major organ has a sensitive period (when it is evolving and developping), critical periods may especially be between 3-8 weeks of pregnancy. For head and nervous system, 5th week. Heart is vulnerable 3.5-6.5 weeks. However, entire prenatal period should be considered as sensitive period for human development. Teratogens can also influence psychological development. Alcohol can cause persons to perform lower on IQ tests of cognitive skills. • Maternal Diseases: some diseases can cross placenta and harm even more the fetus than the pregant woman herself. Rubella: has caused pregnant women to deliver blind babies. Also, can cause deafness, cardiac abnormalities, and mental retardation. Substantially higher risk for the developmental of psychotic disorders than did those that were not exposed to rubella. 60-85% of babies whose mother were exposed had rubella in first 8weeks of pregnancy will have birth defects, compared to 50% in thirs trimester, and 16% for those in week 13-20. Sensitive-period principle. Risk of eye and heart defects are greatest in first 8weeks; deafness when mother is week 6 through 13. Other Infectious diseases: toxoplasmosis (parasite found in many animal) by eating undercooked meat or handling animal's feces that has eaten an infected animal.This cose mild cold-like symtomps in mother, but for babies in womb, serious brain and eye damage. can also induce miscarriage. STIs: capable of pruducing serious birht defects.(genital herpes syphilis, AIDS) • Drugs: Even mild drugs can have lasting efects on developing embryo. The thalidomide tragedy: mild tranquilizer pregnant women took to alleviate nausea and vomiting, gave birht to babies with severe defects. Some even displayed phocomelia (structural abnormality in which some parts of body missing and Flipper as feet). Effect of drug depended when it was taken. if 21st days, baby born w/o ears. if 25th- 27th day then no arms. But some mothers also delivered healthy babies. Other common drugs: Heavy use of aspirin -> fetal growth retardation poor motor control, infant death. Use of ibuprofen -> in 3rd trimester increases risk of prolonged delivery and pulmonary hypertension in babues. heavy use of caffeine -> complications as miscarriage and low birth weight. Antidepressants (containing lithium)-> can produce heart defects if takend 1st trimester. Hormones/contraceptive pill ->sligthly increase of heart defects in embryo. Diethylstillbestrol (DES) sex hormone -> was prescribed for prevention of miscarriage, but women 17-21 yrs whose mother took it, were at risk of developing rare cervical cancer and abnormalities of reproductive system. and more likely to miscarry if get pregnant. Alcohol: Fetal Alcohol Syndrome (FAS) -> physical and neurobehavioral defects. Fetal Alcohol Effects (FAE) now as ARND (Alcohol related neurodevelopmental disorder)-> when neural behavior in absence of physical defects. can cause microcephaly (small head) and malformation of heart, limbs, joints and face. babies likely to display irritab ility, hyperactivity, seizures, and tremors. smaller than normal. IQ score lower than normal babies. 90% display major adjustment problems as adolescents and young adults.There is no safe amount of alcohol that can be consumed during pregnancy! MRI has revealed structural abnormalities in brain of children with FAD. Depressive symptoms at age 6, and more present in girls. It can affect male reproduction aswell, by reducing sperm motility, lower sperm count and abnormally formed sperm. Cigarrette smoking: In 3rd trimester is the most negative period for fetus. A possitive association between smoking in 1st trimester and cleft lip(with or w/o cleft palate). somking retards rate of fetal growth and increases risk of miscarriage. low-birth babies. Schuetze and Zeskind (2001) reported that smoking during pregnancy may also affect the regulation of autonomic activity in neonates. Heart of neonates beat more rapidly when exposed to nicotine. Nicotine diffuses rapidly through placenta. (15% more concentrated). Can have long term effects in cognitive performance, but so far, we only know until 16yrs of age. (beyond that, no diff. found) illicit drugs: Variety of cognitive and behavioral defects are associated with this. exposure to marijuana is associated with changes in functioning of basal nucleus of amygdala (regulation of emotion). Can cause behavioral distubrance that put them at risk for adverse outcomes later in childhood. Will present more symotoms of anxiety and depression. Women more likely to miscarry. Addicted infants experiece withdrawal symptoms such as vomiting, dehydration, convulsions, extreme irritability, weak sucking, high pitched crying. Babies born who were exposed to drugs, were placed in foster homes with special care, and showed development improvements. Environmental factors. Also, boys are more vulnerable to the effects of maternal prenatal drug abuse. Babies whose mother used cocaine or crack more likely to be born prematurely with defects; might be impaired visual-spatial abilities. • Environmental Hazards: Radiation: In japan, 75% of pregnant women had babies who died shortly after when atomic blast happened. Avoid x-rays b/c possibility of developping complications. Chemicals and Polluants: So many in our environment. Women exposed to heavy metals such as lead, zinc, mercury can give birth to babies with physical health impariment and mental abilities impairment. PCBs give low weight babies. also associated with difficulty in maintaining atention, difficulty with spatial reasoning skills and slower reaction time. 9yr olds who breastfed did even more porrly (because extended exposure to PCB) in complex task. Can affect father's sperm. Maternal Characteristics • The mother's diet: before ti was said to gain about 7-8 kg to ensure a healthy development; but now it is 11-14kg. Severe malnutrition can disrupt the formation of the spinal cord and induce miscarriages. During 3rd trimester, more likely to result in low-weight babies, with small heads and may fail to survive. They show severe cognitive deficits. those who do not gain weight will have irritable temperament. Dietary suplements with responsive parents can help eliminate long term damage or prenatal nutrition. In canada, poor women are at risk for poor nutrition. Programs are established to give nutritional supplement programs. Also, women may have plenty to eat but fial to obtain all vitamins and minerals necessary. adding small amount of magnesium and zinc improves functioning of placenta and reduces incidence of many birth complications. Dev. organism needs iodine to ensure normal thyroid functioning. Need folic acid, B-complex vitamin found in fresh fruits, beans,... to help prevent down syndrome, as well as spina bifida, anencephaly, and other defects of neural tube. (@ least 0.4mg/day). especially important from time of conception through first 8 weeks. High dose of vit. A can produce birht defects. • The mother's Emotional Well-Being: when women become emotionally aroused, their gland produce adrenaline/ other stress hormones. Severe emotional stress is associated with low birth weight, premature delivery, decreased fetal motor activity, other... Dipierto, Costigan and Gurewitch (2003) found thast increased vbariability in fetal heart rate and decreased motor activity were associated with increased maternal stress during task. may be caused by sensory experience fetus has. babies tend to be highly active, irritable and irregular in their feeding,sleeping and bowel habits.. Have higher cortisol in blood. Van der Bergh and Marcoen (2004) long term consquences associated with sensitive periods can cause ADHD. (12-22 weeks of pregnancy). also stress can weaken immune system in pregnant women, so can catch more infectuous diseases. The important thing is her ability to manage stress, stress at some point in pregnancy (second trimester) is good, b/c increases motor and mental development at age 2 cause by glucocorticoids (stress hormone that promotes growth). but all depends on ability of mother to manage stress. • The mother's Age: safest time to bear a child is between 16-35 yrs. younger than 16 experience more complications. To add to this, foten they are in poor confitions, poor nutrition, impoversihed family backgrounds. usually not at risk when they receive good health care. after age 35, incidence of miscarriage. conceiving children with chromosomal abnormalities. Prevention of Birth Defects: majority of birthrs are health
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