BIO170 - Obj 7 - Teratogens
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| What is a teratogen? | any agent or substance which can cause developmental abnormalities in the developing embryo/fetus
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| What are the effects of a teratogen? | they can vary widely in severity (no apparent consequence, altered/abnormal growth, carcinogenesis, or embryonic/fetal death)
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| What is teratogenicity? | the capability of causing developmental abnormality
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| What are some examples of teratogens? | pharmaceutical drugs (ex: thalidomide), alcohol, smoking, recreational drugs, infections, radiation, and maternal disease
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| Where was thalidomide originally distributed? How was it marketed? | thalidomide was widely distributed in Europe & Australia as a sleeping pill and to prevent morning sickness and miscarriage
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| What were the effects of thalidomide? | children born to mothers who had taken thalidomide in early pregnancy showed gross development abnormalities, especially missing and/or shortened limbs
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| What legislation was passed due to thalidomide? | the Pure Food and Drug Act of 1962
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| What are other medications with know teratogenicity? | accutane (a vitamin A derivative used to treat severe acne), tetracycline (an antibiotic - causes problems with bone development), and antidepressant medications
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| What is FAS? | fetal alcohol syndrome - collective disorders caused by alcohol consumption during pregnancy?
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| What are the clinical signs of FAS? | slowed growth, developmental delays, behavioral disturbances, and craniofacial abnormalities
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| What are examples of craniofacial abnormalities associated with FAS? | microcephaly and visual impairments; in extreme cases, the infant's eyes may fail to develop
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| At what point during pregnancy is alcohol safe? | pregnant women are currently advised to abstain from alcohol during the entire period of pregnancy
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| What are the direct effects of maternal smoking? | decreased oxygen delivery to the embryo/fetus; smoke contains carbon monoxide which has a higher affinity to iron in hemoglobin that oxygen (approximately 300 times)
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| What risks are increased due to maternal smoking? | pre-term birth, low birth weight, spontaneous abortion (miscarriage), SIDS following birth, abruptio placentia, and placenta previa
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| What is abruptio placentae? | premature separation of the placenta from the wall of the uterus, causing severe hemorrhage to both mother and fetus
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| What are other causes of abruptio placentae? | polyhydramnios (excessive amniotic fluid), multiple gestation, maternal hypertension, increased maternal age, alcohol, and substance abuse
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| What is placenta previa? | the abnormal placement of the placenta (i.e. close to, or covering the cervix) ;mother and fetus are at risk of hemorrhage
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| Where is the optimum placement for the placenta? | on the upper uterine wall
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| What are the effects of marijuana on the fetus? | causes tremors and increased startle reflexes in newborns of marijuana smoking mothers
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| What are the effects of cocaine on the fetus? | vasoconstriction to the uterine smooth muscle (->increased miscarriage risk); also, abruptio placentae, intrauterine growth retardation, pre-term birth; infants can be addicted at birth, suffer stroke-like disorder, and other neurobehavioral abnormalities
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| What are the effects of heroin on the fetus? | many of the same complications as cocaine; additionally, addicted mothers are more susceptible to life-threatening infections and AIDS
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| What are the 2 ways maternal infection may harm the fetus? | 1) microorganisms may damage the embryo/infant directly or 2) microorganisms may alter the maternal environment causing damage to the embryo/fetus
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| What are some of the effects of maternal infection? | miscarriage, premature birth, congenital defects, and/or growth retardation
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| What are the most common infections in the US which cause fetal damage? | STORCH - syphillis, toxoplasmosis, rubella, cytomegalovirus, and herpes simplex
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| What are the effects of ionizing radiation on the fetus? | causes damage to the genetic material; in high doses, can cause death; in lower doses can cause congenital abnormalities, growth retardation, and increased cancer risk later in life
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| What are examples of maternal disease that impact the fetus? | diabetes mellitus, anemia, heart disease, and other chronic conditions can affect development
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| What is the major impact on the etiology of teratogens? | timing and dosage are very important; generally, exposure to a teratogen very early or very late in pregnancy tends to be less damaging; during critical periods of development, exposure to a teratogen can harm or kill the embryo/fetus
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| What stage of development is the embryo in the first 2 weeks following conception? | embryo is travelling thru the fallopian tubes; implantation has not yet occurred; not yet a connection between maternal/fetal circulation
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| What is the effect of exposure to teratogens the 1st 2 weeks following conception? | exposure to low to moderate levels of a teratogen may cause no abnormality in the embryo; exposure to high levels of a teratogen may cause prenatal death (before the mother even realizes that she is pregnant)
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| What is occuring in the development of the embryo in weeks 2-5? What is the impact of a teratogen during this time? | rapid development of the CNS and circulatory systems; development of the eye and limb buds; exposure to a teratogen can affect development of these systems and may cause major structural abnormalities and/or death of the embryo
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| What occurs during weeks 4-7 of embryonic development? What is the effect of a teratogen during this time period? | nervous system, heart, eyes, ears, limbs, mouth, teeth are developing; exposure may affect these systems/organs; effects: death, major or minor abnormalities in structure/function; cleft lip & palate typically occur to problems during this time period
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| What are the effects of a teratogen during weeks 6-10 of embryonic development? | depending on the dosage, affects include abnormalities of the CNS, heart, special senses, limbs, digestive system; also external genitalis begin to develop during the latter part of this period and their development may be affected by exposure
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| When does the CNS develop in the embryo/fetus? | the CNS is developing from conception until delivery; teratogens can affect the CNS during any stage of development
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