Fetal Growth and Development AND ENVIRONMENTAL TOXINS Spermatogenesis The process of making sperm Oogenesis The process of making eggs Ovulation The release of an egg ova 14 days after the onset of menses Production of progesterone tells her body that she is pregnant Female sex hormones LH Luteinizing hormone Stimulates ovulation progesterone secretion mammary glands and male testosterone secretion FSH Follicle stimulating hormone Stimulates follicle development and other sex hormones Estrogen Class of hormones secreted from the ovarian follicle Considered the main female hormones Progesterone Maintains endometrium during pregnancy Female hormonal regulation Ok so you have had sex Are you pregnant What is pregnant If you had sex on Friday February 14th Fertilized on Wednesday February 23rd Implantation on Saturday March 1st When did you become pregnant When do you find out you are pregnant Fertilization The production of a zygote How does the egg get fertilized Where does fertilization take place How long does it take Steps during fertilization Sperm approaches egg Sperm releases enzymes Sperm bonds with ova Ova membrane changes Gestation The condition of carrying a developing baby within the uterus How long is a pregnancy 266 days 38 weeks Mice 29 days Elephants 22 months What is the average size of a baby 50 cm 20 inches and 2 7 4 5 kg 6 10 lbs What happens in the first month The zygote splits every 20 minutes In three hours a single ball of cells forms This continues to divide for three more days Step 1 Zygote Blastula Formation of a hollow ball of cells This is completed by day 5 Step 2 Blastula Gastrula The tissues migrate becoming quite different Ectoderm NS and skin Mesoderm Heart kidney Endoderm Digestive tract Changes in the gastrula The placenta Why is the placenta important Fully formed at 31 days Movement of nutrients and waste products Some things can pass the placenta German measles HIV Tetracycline There is no contact between the mother and fetal blood Stages of Development The first trimester Basically discussed already Fertilization until about 11 weeks At nine weeks Embryo is now called a fetus 5 5 cm long All organs are present Limb buds have tiny arms and legs fingers toes At the end sex is usually apparent The embryo one week after implantation Initial Developmental Stages The four week embryo The 5 week embryo At the end of the first trimester The major initial developmental steps have been completed Embryo s still have pharyngeal gill slits webbing on toes and fingers Second trimester 12 to 24 weeks Size and overall features develop 14 wks 6 cm 20 wks 19 cm 500 g Mothers abdomen becomes enlarged Third trimester 24 weeks to birth Features Fetus grows and gains strength Internal temperature regulation Systems get ready for oxygen Bones harden muscles thicken Loss of fetal fur Head changes proportions Parturition Objective Assess our understanding of how chemicals affect child health Overview Protect children from neurotoxic exposures from environmental toxins a Goal The Undecided Dose Too much of a thing makes you blue But not having it can kill you too Too much or too little Let s not be so fickle We ll go Dutch and divide it by two Children are not little adults Exposure starts early preconception breast milk For their body weight children eat and breathe more than adults thus a small exposure translates into a big dose Brain developing cells dividing Behavior hand to mouth increases exposure to chemicals Timing of exposure A child s developing nervous system is more sensitive to chemical exposures than the adult nervous system Other environmental factors Pharmaceuticals Genetic factors Environmental justice socioeconomics nutrition and stress Environmental Agents Environmental agents that we are confident cause learning and developmental disabilities in humans Alcohol Lead Mercury PCBs PBDEs Manganese Arsenic Solvents PAHs Pesticides Nicotine ETS Before we start discussing toxins We will focus on environmental toxins and DEVELOPING humans infants and children as this is when the most profound effects can be seen The ramifications are that that these toxins also effect adults as well but to a lesser degree Toxins can accumulate in the body especially the fatty tissue Alcohol Fetal Alcohol Spectrum Disorder FASD is the most preventable form of behavioral and learning disabilities In the US FASD is estimated to affect 9 1 per 1000 infants with even higher rates in other parts of the world Do not consume alcohol during pregnancy Lead There is no safe level of lead exposure for children Even the lowliest of lead exposure cause impairs overall intelligence as measured by IQ learning and memory The CDC should lower the blood lead action level Rationale for Lowering the Blood Lead Action Level From 10 to 2 g dl Steven G Gilbert and Bernard Weiss Neurotoxicology Vol 27 5 September 2006 pp 693 701 Mercury Mercury bioaccumulates in fish Mercury is distributed in the environment by coal burning electric utility plants Mercury advisories limit fish consumption for women and children US EPA RfD 0 1 ug dL PCBs Polychlorinated biphenyls Highly persistent and bioaccumulative Stored in fat and excreted in women s breast milk Exposure can adversely affect motor skills learning and memory as shown in lower fullscale and verbal IQ scores and reading ability PBDEs Polybrominated diphenyl ethers Commonly used as flameretardant PBDEs structurally similar to PCBs Bioaccumulates in animals and humans and are excreted in human breast milk O Developmental neurotoxicants Brx Bry Arsenic Commonly found in drinking water around the world sometimes in concentrations high enough to cause cancer Dose response relationship between exposure to arsenic and intellectual impairment Solvents Broad array of different compounds including toluene benzene alcohol turpentine acetone and tetrachloroethylene TCE More than 50 million metric tons used in the US and more than 10 million people exposed in the workplace PAHs Polycyclic aromatic hydrocarbons Widely distributed air pollutants and wellrecognized human mutagens and carcinogens PAHs are generated during combustion of fuels from motor vehicles coal fired power plants residential heating cooking and tobacco smoke PAHs results in lower birth weight and affects cognitive Pesticides Designed to kill insects plants fungi or animals Agricultural and residential application of pesticides in the US totals more than one billion pounds per year Childhood