Embryology + Teratology Flashcards
What is teratogenesis?
dev of birth defects and malformations (non-reversible internal, external or microscopic)
What is the leading cause of infant death in North America and why?
birth defects
- improvement of obstetrical care
- increased use of medications and social drug use
- environmental contaminants
Why is there an increase in birth defects at 2 yo?
discovery of defects internal organs
may be symptoms less at birth
What are the causes of birth defects?
- known genetic causes and chromosomal aberrations
- maternal illness
- drug and chemicals
- unknown causes
What is the prevalence of normal pregnancies that give birth to healthy infants?
<50%
What is the largest contributor to unsuccessful pregnancy?
postimplantation losses
When the fetus is the most at risk?
organogenesis = teratogenic period (17-54 days post fertilization)
What is hyperplasia?
cell division => increase in cell number
Phase of fertilization when the zygote begins to divide.
blastogenesis
2 cell types in blastocyst:
-embryoblast (inside)
-trophoblast (outside)
What characterized the pre-implantation phase?
< 1 week = increased in cell number but not size
low susceptibility to abnormalities bc poor toxins accessibility
what happens on day 16 of post ovulation?
invagination in the future cranial area
What characterized the gastrulation phase?
- primitive streak = formation of 3 germ layers
- neurulation = ectoderm into neural pate = neural tube
- mesoderm + endoderm form organs and tissues
* VERY susceptible to teratogens*
At which day after fertilization does the neural tube close?
day 27
What are the factors of teratogenic effects of drugs?
- type of drug
- time of exposure
- length of time of exposure
What is cretinism?
- syndrome of mental or physical retardation = caused by iodine deficiency
Which micronutrients can cause neural tube defects?
folate and Zn
What is the consequence of vit K deficiency during pregnancy?
Coumadin syndrome
What are the fetus defects of FAS (fetal alcohol syndrome)?
- growth retardation
- cranial malformations
- decreased fat stores
- retarded intellectual dev (3rd trimester = greatest sensitivity of fetal brain)
Why is the fetus affected by alcohol?
alcohol distributed evenly between mother’s and fetus’ fluids => alcohol enters placenta and BBB freely
fetus can’t properly detoxify and clear = alcohol stays longer in fetus than mother
What are the consequences on metabolism of alcohol consumption during pregnancy?
- replace calories = protein deficiency
- blocks Zn and folate absorption
- converted to acetaldehyde = toxic in smaller qts
- free radicals
- impaired delivery of oxygen and nutrients to placenta
What is the most common NTD?
spina bifida => spinal cord and spinal nerve abnormalities
What was the MRC study?
evaluate prevention of NTD with folate supp or multi-vit
no effect with multi-vit
success of folate supp (71% reduction in NTD with 4mg supp)
Why does folate play a role in fetal dev?
- folate is essential in conversion of homocysteine to methionine => heart defects with low methionine + placenta can dissociate from uterus
- methionine is essential in methylation
- accumulation of SAH => inhibition of methyltransferase => hypomethylation => altered gene expression
- oxidative stress => DNA + cell damage, decrease B12 availability
What folate supp does?
decrease maternal and fetal [homocysteine]
What are the stages of fetus evolution?
oocyte => zygote => morula => blastocyte => embryo => fetus
How the placenta is formed?
trophoblasts secreted enzymes that erode the uterus wall so the blastocyst can be anchored. fluids are absorbed by phagocytosis. then trophoblasts become the placenta
what is microcephaly?
caused by protein deficiency
What are the alcohol-related birth defects
heart + lungs malformations
minor facial abnormalities
microcephaly = mental retardation
