Study Guide for Prenatal Development Infancy Prenatal Development 1 For each of the 3 stages of prenatal development be able to a Name the stage b State when it begins and ends c Describe the specific developments that occur during each period d Know in general terms the kinds of problems that occur when things go wrong Fertilization of Egg Generally during 3 7 day journey of mature egg from ovary down fallopian tube to uterus 3 stages of prenatal development not referring to trimesters 1 Zygote Germinal Period 2 Embryo 3 Fetus Begins fertilization Ends zygote firmly implants in uterine wall 1 Zygote Usually 2 weeks Implantation Tendrils from zygote penetrate uterine wall 60 75 of zygotes survive Many that do not survive have severe genetic defects 2 Embryo Begins Zygote firmly implanted Ends Approximately end of 8th week Period of MOST rapid cell differentiation What does this mean Cells become SPECIALIZED Most organs formed crudely functioning 1st step of differentiation 3 layers form a Ectoderm outer layer outer skin nervous system b Mesoderm middle muscles skeleton blood c Endoderm inner lungs digestive tract Auxiliary structures develop 1 Amniotic sac contains amniotic fluid which protects from changes in TEMP Old cells accumulate in fluid amnion outer membrane of sac 2 Chorion surrounds amnion 3 Placenta outside chorion attached to uterine lining 4 Umbilical cord connects embryo at abdomen to placenta 1 2 4 develop from zygote 3 develops from zygote uterus By end embryonic period 1 Face limbs fingers toes external genitals most internal organs are crudely formed 2 Crude movements of heart liver ingestion 3 Nervous system begins to develop 4 Weight 17 oz Embryo s vulnerability 1 MOST miscarriages in embryonic period 2 Embryos vulnerable to largest of teratogens 3 Type of defects determined by when exposed to teratogen Effects either destruction structural defect or functional defect 3 Fetus Begins start of 9th week 3rd month Ends delivery Summary 1 All organs mature develop further 2 Biggest growth period for what system CNS 3 Finishing touches muscle fat growth 4 Further formation of genitals May see gender by11 12 weeks Reflexes begin 20 weeks 5 months suck hiccup swallow 22 26 weeks If born fetus has some chance of survival Age of Viability previously 28 weeks After 28 weeks gains 1 2 lb per week Full term 38 40 weeks Preterm before 37 weeks 2 The process of cell differentiation a Explain what it is b During what stage of prenatal development does it occur most rapidly c Describe the first step in the cell differentiation process A Cells become SPECIALIZED B Embryonic Period C 1st step of differentiation 3 layers form a Ectoderm outer layer outer skin nervous system b Mesoderm middle muscles skeleton blood c Endoderm inner lungs digestive tract 3 Auxiliary Structures a Be able to name and describe the function of each one b From what does each develop 1 Amniotic sac contains amniotic fluid which protects from changes in TEMP PHYSICAL SHOCKS Old cells accumulate in fluid amnion outer membrane of sac 2 Chorion surrounds amnion 3 Placenta outside chorion attached to uterine lining 4 Umbilical cord connects embryo at abdomen to placenta 1 2 4 develop from zygote 3 develops from zygote uterus 4 Explain the transfer of nutrients wastes between mother and embryo fetus Transfer of nutrients wastes 1 Nutrients oxygen from Mom s blood build up in placenta travel to embryo fetus via umbilical cord 2 Placenta cord attached by semi permeable membrane like a mesh Nutrients oxygen wastes cross membrane What is too big to cross membrane Red Blood Cells Other substances that can cross infections drugs 5 Rh factor c What is it d Describe the condition s under which problems can arise and what happens e What can be done to prevent problems Rh Blood factor Rh HAVE the factor in blood Rh do NOT have factor in blood Baby s Rh can get into Mom s blood if placenta ruptures during some prenatal tests Causes Rh Mom to build antibodies to fight Rh factor Rh factor only problem if Mom Rh baby Rh Rh dominant Rh recessive When can you get Rh baby and Rh mom Positive Father Antibodies generally not problem with 1st baby 6 Thalidomide a What is it b Describe the defects it can cause when taken during pregnancy and what determines whether it will lead to these defects c What is the important lesson s to be learned from the Thalidomide saga A Anti anxiety and anti nausea drug A drug once prescribed to relieve morning sickness in pregnant women but discontinued when found to cause serious fetal malformations B 5th 8th week Critical period for limb formation C Effects of substance during pregnancy depend on 1 nature of substance its effects on body 2 when it is used 7 Age of Viability DURING FETAL STAGE a What is it b When is it c How does the current age of viability differ from the previous age of viability A The point at which the fetuses physical systems are advanced enough that it has a chance to survive if born prematurely B 22 26 weeks C Many systems are still developing Not uncommonly babies are born before 28 weeks later display developmental deviations especially if they encounter other adverse environmental conditions 8 Weight of baby a Typical weight at end of embryonic period b Typical weight at birth c Define low birth weight A Length 1 1 inches Weight 0 09 oz 0056 lbs B Normal size average 7 7 lbs 5 5 12 and 20 C Less tha 5 5 lbs whose weight is less than appropriate for their time in utero are called SMALL FOR DATE babies 9 Preterm or Low Birth Weight Babies a What are common causes b What are problems that result c How can parents minimize problems d Describe the Breathing Bear and its effects on premature infants from text A Common Causes 1 Multiple babies 2 Problems with uterus placenta 3 Smoking alcohol drugs 4 High blood pressure diabetes 5 Major stress 6 Poor health weight extremes B Problems associated w preterm 1 brain central nervous system restlessness inattention speech hearing learning probs 2 respiratory allergies asthma C How to minimize problems 1 physical psychological stimulation fit treatment to individual 2 responsiveness 10 Newborn Testing I In general what kinds of tests are required versus optional a b What kind of examination is done at birth in text States require tests of common e g PKU hypothyroid Optional tests 30 rare disorders Some treatable deadly if not treated 11 Prenatal Testing For each test listed be able to explain when it is typically done how it is
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