Chapter 2: Prenatal Development and the Newborn PeriodI. Prenatal DevelopmentA. Conception1) Epigenesisa) Emergence of new structures and functions during development2) Gametesa) Reproductive cells; i.e. eggs or spermb) Only contain 23 chromosomes (no pairs)c) Created via meiosis3) Zygotea) Fertilized eggb) 46 chromosomes (23 pairs)c) Beginning of germinal prenatal staged) Grows via mitosis(i) Process of duplication and divisionB. Developmental Processes1) Periods of Prenatal Developmenta) Germinal(i) Conception up to two weeks(ii) Ends when zygote attaches itself to the uterine wall(iii) Rapid cell division takes placeb) Embryonic(i) Three to eight weeks following conception(ii) Major development of the organs and systems of the bodyc) Fetal(i) Nine weeks to birth(ii) Rapid growth of the body(iii) Increasing levels of behavior, sensory experience, and learning2) Steps Allowing For Transformation of the Zygotea) Cell division(i) Zygote continually splits into two cells for each existing cell(ii) Continues for all 38 weeks of gestationb) Cell migration(i) Cell movement from point of origin to designated spotsc) Cell differentiation(i) Stem cells- All embryonic cells initially- No specialized function(ii) Differentiate into 350 types of cellsd) Cell death(i) “cell suicide”- Apoptosis(ii) Necessary for developmental processes(iii) e.g. development of individual fingers of the hands3) Role of Hormonesa) Genetic material doesn’t have a direct effect on development of male or female genitaliab) Testosterone, or lack thereof, generated by the fetus itself causes to become male or femaleC. Early Development1) Twinsa) Identical twins(i) Monozygotic(ii) Inner cell mass splits during early mitosis(iii) 1 in 250 live birthsb) Fraternal twins(i) Dizygotic(ii) As genetically similar as two siblings(iii) 1 in 30 live births 2) Extra-embryonic Supportsa) Amniotic sac(i) Transparent, fluid-filled membrane that protects the fetus in gestation(ii) Allows fetus to practice using its musclesb) Placenta(i) Nutrient rich blood vessel network(ii) Allows for transfer of nutrients and minerals(iii) Umbilical cord contains blood vessels from placenta to fetus(iv)Produces hormones such as estrogen and progesterone- Estrogen increases blood flow to the fetus- Progesterone limits uterine contractions that could lead to premature labor3) Cephalocaudal Developmenta) Phenomenon of areas near the head developing before areas further awayD. Fetal Behavior1) Movementa) Fetus begins to bend its head at 5 or 6 weeksb) Hiccups begin at 7 weeksc) All movements present at birth are present at 12 weeksd) Fetal breathing(i) Breathing in/swallowing of amniotic fluid(ii) Practiced beginning at 10 weeks(iii) Only occurs 50% of the time(iv)Helps develop digestive system2) Behavioral Cyclesa) Fetus only moves 10-30% of the time during the second half of pregnancyb) When nearing birth, fetuses spend almost all of their time in REM sleepE. Fetal Experience1) Sighta) Very little to seeb) 26 weeks – can experience changes in light2) Toucha) Fetus can explore its own body and its environment3) Tastea) Fetuses prefer sweet tastes as opposed to standard amniotic fluid4) Smella) Amniotic fluid absorbs the odors of whatever the mother has recently consumedb) When fetus swallows the fluid, he/she can smell whatever is in it5) Hearinga) Starting to develop at end of 2nd trimesterb) Fetus can hear some external sounds:(i) People talking to the mother(ii) Mother’s voicec) Internal sounds – 75 Db(i) Mother’s heartbeat(ii) Mother’s breathing(iii) Vascular system(iv)Mother’s digestive tract6) Motiona) Vestibular system developed at 5 monthsF. Fetal Learning1) Fetuses are able to learn once their central nervous system develops (6 months)a) Able to distinguish between noises and become habituated to repeated stimuli2) Preferencesa) Infants prefer familiar sounds, scents, and tastesb) Preferences are persistent3) Heartbeat Experiment (1970s)a) Group 1: normal maternal heartbeatb) Group 2: fast maternal heartbeatc) Group 3: no heartbeatd) Results:(i) Group 1 > Group 3 > Group 2 in terms of babies’ response to normal heartbeat4) Maternal Vocal Learninga) Pregnant moms read The Cat in the Hat twice/day for six weeksb) Newborns changed sucking rate to turn on familiar or novel story(i) Newborns wanted to hear familiar story5) Prenatal Learninga) Prenatal education programs, including the following, do not work(i) Learning books through excessive reading(ii) Recognizing Daddy’s voice by using a megaphone(iii) Learning music through excessive listeningb) Baby may only develop preferences for mother’s voicec) Baby will quickly recognize Dad’s voice after birth anywayG. Hazards to Prenatal Development1) Environmental Influencesa) Minamata disease(i) Methyl-mercury poisoning(ii) Lead to:- Human illnesses- Bizarre behavior in cats- Intellectual disabilities, cerebral palsy, seizures, blindness, deafness(iii) Caused by local seafoodb) Teratogens(i) Chemical agents that infiltrate the fetus’ vascular system and lead to damage or deathc) Sensitive period(i) Period of time in which the fetus is the most sensitive to harmful teratogens(ii) Different for various parts of the body(iii) Most sensitive periods begin before a woman might realize she is pregnantd) Prospective longitudinal (PL) design(i) Initial measure at or before birth(ii) Study effects of conditions far into futuree) Dose-response relation(i) Greater exposure to a harmful substance leads to greater effect and damage onthe childf) Fetal programming(i) Delayed emergence of the effects of the prenatal environmentg) Sleeper effects(i) A side effect of an agent that lies dormant for a long period of time following birthh) Legal Drugs(i) Cigarette Smoking- Fetus receives less oxygen- Fetus may metabolize cancer-causing agents in tobacco- 13% of women smoke during pregnancy- Consequences Delayed growth Low birth weight(ii) Alcohol- Most common human teratogen- 15-20% of women drink during pregnancy- Blood levels in mother and child are equal, but fetus has lower ability to remove alcohol from blood- Fetal Alcohol Spectrum Disorder (FASD) Fetal Alcohol Syndrome Autism Spectrum Disorder symptoms Attention deficits Hyperactivity Fetal Alcohol Effects Similar but less severe symptomsi) Illegal Drugs(i) 4% of pregnant women use illicit drugs(ii) Marijuana most