Lecture 4Outline of Last Lecture I. Biological FoundationsA. The Genetic CodeB. Chromosomes, Cells, and SexII. Patterns of Genetic InheritanceIII. Behavior Genetics ResearchA. FindingsB. Reaction RangeIV. Genetic – Environmental CorrelationV. Chromosomal AbnormalitiesOutline of Current Lecture VI. Stages of Prenatal DevelopmentA. Germinal, Embryonic, and Fetal VII. Risk Reduction and DeterminationVIII. Types of TeratogensIX. Three Stages of LaborX. Methods of DeliveryXI. Birth WeightA. Pre-Term, Low Birth Weight and Small for Gestational AgeCurrent LectureThere are three stages of prenatal development: Germinal, Embryonic, and FetalGerminal: first stage that occurs 0-2 weeks after conception. Conception occurs in the Fallopian Tubes. After ten days the Zygote moves down and is implanted in the uterus (around 60% of zygotes fail to implant). During the germinal period cells undergo multiplication and differentiation:Blastocyst: the entire mass of the developing zygote (very few cells)Embryonic Disc: the fetus, developed from the blastocystTrophoblast: composed of the placenta (provides oxygen and nutrients to the fetus) and the umbilical cord (attached to the site of the bellybutton and the placenta).Embryonic Period: second stage that occurs 3-8 weeks after conception. Here the embryonic disc forms three layers: the Ectoderm (the neural tube –spinal cord location), Mesoderm (from which connective tissue, urogenital system and circulatory system develops), and the Endoderm (from which the gastrointestinal tract, and lungs are developed). The embryonic period is most critical for structure development – everything is there, it just needs to get bigger. By the end of this stage the embryo weighs about 1/30 of an ounce. PSYCH 250 1st EditionFetal Period: this is the growth and finishing phase. The gestation period for humans can be organized into 3 trimesters.1st Trimester- Fetus is 3 months, 3 oz. & 3 inches- Sex organs develop by the 12th week2nd Trimester- “Quickening” between 17-20 weeks- Covered in thick cheese-like substance, meant to protect skin from amniotic fluid (over-term babies often appear dry and chapped as substance wears off)- A layer of hair over the body helps keep substance on3rd Trimester- Extensive brain maturation- Central nervous system becomes very sensitive- Babies are responsive to sound and pain. - By third trimester, a layer of fat develops to help regulate temperature, and baby begins receiving antibodies from motherEarly evidence of personality and temperament can observed while the child is still in the womb. High activity in the womb has been linked to activity in childhood and greater ability to cope with stress.Age of Viability: earliest age at which a developing child could survive outside the womb if it is born early. This occurs about halfway through the 2nd trimester at 22 weeks gestation. Weight plays a critical role in the survival of the baby outside the womb. Babies born premature, who weigh less than 1 ½ lbs,have only a 20% survival rate. However, if by 28 weeks, the baby’s weight has increased to at least 3 lbs., the survival rate jumps to 95%.Risk ReductionRisks to the health and development of the fetus arise from Teratogens. Teratogens are any environmental agent that causes damage to developing organism (diseases, lifestyle, drug use, and medications). It is important to take precautions when you’re pregnant – anything is a potential hazard.Ex: In the 40s-60s it was discovered that the placenta does protect against drugs, and exposure to disease (babies on a particular World War 2 base were born blind after mothers were exposed to rubella) Birth defects occur in about 5-8% of all births, and 20% of these defects arise from an unknown origin.Determining Risk: Timing of Exposure, Amount of Exposure and Genetic Vulnerability all play a key role in determining the effects of a teratogen on an unborn child.Timing - Throughout development are sensitive periods: the time of greatest vulnerability (for each body structure)- Ex: eyes are forming at the time the mother is exposed to rubella, the child’s eyes are affectedAmount - Threshold effect – a little exposure wouldn’t hurt, lots of exposure would- Interaction effect –one substance wouldn’t have a huge impact but the interaction betweenthat substance and another substance can be largely detrimental.Genetics - Ethnicity - Sex (males at greater risk for learning disabilities, and are also more likely to die earlier)Types of Teratogens Drugso Prescription & Nonprescriptiono Illegal  Tobacco – 12% of women in the U.S. smokeo Leads to low birth weight, SIDS, childhood cancero Exposure to smoke (even 2nd hand) can be detrimental Alcohol (Fetal Alcohol Syndrome) Radiation  Pollution Infectious diseases (e.g., HIV/AIDS)HIV & Pediatric AIDS: Roughly 20-30% of babies born to HIV+ mothers contract the disease themselves. However, less than 5% of babies contract HIV/AIDS if their prenatal care includes: antiretroviral drugs, C-section, and no breast finding at all post-delivery.Fetal Alcohol Syndrome: caused by heavy drinking (5 or more drinks per day), and causes widespread developmental delays including cognitive, physical and behavioral defects. Large amounts of alcohol affect the migration and production of the fetus’s neurons (arrested brain development). This is because it takes large amounts of oxygen to metabolize alcohol. The oxygen is taken from the mother’s body which means that less oxygen is available to the brain of the fetus. FAS is the leading behavioral cause of mental retardation.Fetal Alcohol Effects: milder form of FASThe Stages of Labor1. Dilation and Effacement of Cervix - is generally the longest stage, the goal is to get to 10 centimeters, lasts 12-14 hours for a first pregnancy 2. Delivery of Baby - First baby usually takes about an hour (any longer than 2 will mostly likely result in a C-section)3. Delivery of Placenta - Placenta takes a few minutes – if it doesn’t detach appropriately women can bleed out very quicklyMethods of DeliveryMost deliveries take place in a hospital, about 5% occur in birthing centers and 1% of pregnant mother choose in-home birth.Doula: a doula is someone who assists women with labor, delivery, and breast-feeding. A study of 420 middle-class pregnant women was conducted to determine the effects of a doula. Study: 420 middle class women were