Embryology + Teratology

Question 1

What is teratogenesis?

Answer 1

dev of birth defects and malformations (non-reversible internal, external or microscopic)

Question 2

What is the leading cause of infant death in North America and why?

Answer 2

birth defects

• improvement of obstetrical care
• increased use of medications and social drug use
• environmental contaminants

Question 3

Why is there an increase in birth defects at 2 yo?

Answer 3

discovery of defects internal organs

may be symptoms less at birth

Question 4

What are the causes of birth defects?

Answer 4

• known genetic causes and chromosomal aberrations
• maternal illness
• drug and chemicals
• unknown causes

Question 5

What is the prevalence of normal pregnancies that give birth to healthy infants?

Answer 5

<50%

Question 6

What is the largest contributor to unsuccessful pregnancy?

Answer 6

postimplantation losses

Question 7

When the fetus is the most at risk?

Answer 7

organogenesis = teratogenic period (17-54 days post fertilization)

Question 8

What is hyperplasia?

Answer 8

cell division => increase in cell number

Question 9

Phase of fertilization when the zygote begins to divide.

Answer 9

blastogenesis
2 cell types in blastocyst:
-embryoblast (inside)
-trophoblast (outside)

Question 10

What characterized the pre-implantation phase?

Answer 10

< 1 week = increased in cell number but not size

low susceptibility to abnormalities bc poor toxins accessibility

Question 11

what happens on day 16 of post ovulation?

Answer 11

invagination in the future cranial area

Question 12

What characterized the gastrulation phase?

Answer 12

1. primitive streak = formation of 3 germ layers
2. neurulation = ectoderm into neural pate = neural tube
3. mesoderm + endoderm form organs and tissues
   * VERY susceptible to teratogens*

Question 13

At which day after fertilization does the neural tube close?

Answer 13

day 27

Question 14

What are the factors of teratogenic effects of drugs?

Answer 14

• type of drug
• time of exposure
• length of time of exposure

Question 15

What is cretinism?

Answer 15

• syndrome of mental or physical retardation = caused by iodine deficiency

Question 16

Which micronutrients can cause neural tube defects?

Answer 16

folate and Zn

Question 17

What is the consequence of vit K deficiency during pregnancy?

Answer 17

Coumadin syndrome

Question 18

What are the fetus defects of FAS (fetal alcohol syndrome)?

Answer 18

• growth retardation
• cranial malformations
• decreased fat stores
• retarded intellectual dev (3rd trimester = greatest sensitivity of fetal brain)

Question 19

Why is the fetus affected by alcohol?

Answer 19

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

Question 20

What are the consequences on metabolism of alcohol consumption during pregnancy?

Answer 20

• 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

Question 21

What is the most common NTD?

Answer 21

spina bifida => spinal cord and spinal nerve abnormalities

Question 22

What was the MRC study?

Answer 22

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)

Question 23

Why does folate play a role in fetal dev?

Answer 23

• 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

Question 24

What folate supp does?

Answer 24

decrease maternal and fetal [homocysteine]

Question 25

What are the stages of fetus evolution?

Answer 25

oocyte => zygote => morula => blastocyte => embryo => fetus

Question 26

How the placenta is formed?

Answer 26

trophoblasts secreted enzymes that erode the uterus wall so the blastocyst can be anchored. fluids are absorbed by phagocytosis. then trophoblasts become the placenta

Question 27

what is microcephaly?

Answer 27

caused by protein deficiency

Question 28

What are the alcohol-related birth defects

Answer 28

heart + lungs malformations
minor facial abnormalities
microcephaly = mental retardation