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BIO170 - Obj 7
BIO170 - Obj 7 - Teratogens
| Question | Answer |
|---|---|
| What is a teratogen? | any agent or substance which can cause developmental abnormalities in the developing embryo/fetus |
| What are the effects of a teratogen? | they can vary widely in severity (no apparent consequence, altered/abnormal growth, carcinogenesis, or embryonic/fetal death) |
| What is teratogenicity? | the capability of causing developmental abnormality |
| What are some examples of teratogens? | pharmaceutical drugs (ex: thalidomide), alcohol, smoking, recreational drugs, infections, radiation, and maternal disease |
| 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 |
| 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 |
| What legislation was passed due to thalidomide? | the Pure Food and Drug Act of 1962 |
| 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 |
| What is FAS? | fetal alcohol syndrome - collective disorders caused by alcohol consumption during pregnancy? |
| What are the clinical signs of FAS? | slowed growth, developmental delays, behavioral disturbances, and craniofacial abnormalities |
| What are examples of craniofacial abnormalities associated with FAS? | microcephaly and visual impairments; in extreme cases, the infant's eyes may fail to develop |
| At what point during pregnancy is alcohol safe? | pregnant women are currently advised to abstain from alcohol during the entire period of pregnancy |
| 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) |
| 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 |
| What is abruptio placentae? | premature separation of the placenta from the wall of the uterus, causing severe hemorrhage to both mother and fetus |
| What are other causes of abruptio placentae? | polyhydramnios (excessive amniotic fluid), multiple gestation, maternal hypertension, increased maternal age, alcohol, and substance abuse |
| 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 |
| Where is the optimum placement for the placenta? | on the upper uterine wall |
| What are the effects of marijuana on the fetus? | causes tremors and increased startle reflexes in newborns of marijuana smoking mothers |
| 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 |
| 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 |
| 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 |
| What are some of the effects of maternal infection? | miscarriage, premature birth, congenital defects, and/or growth retardation |
| What are the most common infections in the US which cause fetal damage? | STORCH - syphillis, toxoplasmosis, rubella, cytomegalovirus, and herpes simplex |
| 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 |
| What are examples of maternal disease that impact the fetus? | diabetes mellitus, anemia, heart disease, and other chronic conditions can affect development |
| 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 |
| 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 |
| 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) |
| 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 |
| 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 |
| 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 |
| 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 |
Created by:
debmurph
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