Unit 5- Embryology & Teratology
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What’s re 3 trimesters of pregnancy?
• 1st trimester- Zygote develops into a multicellular embryo, then a foetus with major organ beginnings. • 2nd trimester- Organs further develop; foetus becomes recognisably human. • 3rd trimester- Organs become functional; rapid growth & fat accumulation.
What occurs during days 1-6 of prenatal development?
Fertilisation & cleavage (formation of blastomeres).
What occurs during day 7 of prenatal development?
Implantation occurs.
What occurs on day 20 of prenatal development?
The neural tube begins to form (central, peripheral , & enteric nervous systems).
What occurs on day 22 of prenatal development?
Myogenic activity in the heart begins.
What occurs on days 26-28 of prenatal development
Limb buds & eyes begin to form.
What occurs on day 28 of prenatal development?
A basic gastrointestinal tract is present.
What developmental milestone occurs on day 33?
The cerebral cortex begins forming.
What occurs on day 36 of prenatal development?
Kidneys start developing.
What occurs on day 46 of prenatal development?
Ovaries & testes differentiate microscopically.
What occurs on day 54 of prenatal development?
Major blood vessels take their adult pattern.
What occurs on day 56 of prenatal development?
Most organs & systems are developed.
What are teratogens?
Agents causing malformations in an embryo or foetus.
What occurs on the 10th week of prenatal development?
Fingernails & toenails begin to develop.
What occurs during the 4th month of prenatal development?
Fine palm lines have formed that can be used to permanently identify the child.
What are the factors affecting the ability of a teratogen to affect a developing foetus.
• Nature of the agent itself • Route & degree of maternal exposure • Rate of placental transfer & systemic absorption. • Composition of the maternal & embryonic/foetal genotypes.
What are the 4 results to the foetus of deviant development?
• Death • Malformation • Growth retardation • Functional defect
How does ACE inhibitors affect foetal development?
Safe in the 1st trimester but can cause renal tubular aplasia & growth retardation in the 2nd & 3rd trimesters.
Why & when should satins be avoided in pregnancy?
They are teratogenic & should be stopped 3 months before conception.
What risks are associated with anti-epileptic drugs (AED’s) during pregnancy?
Most AEDs are teratogenic, but the risk can be reduced with monotherapay. Risks must be weighed against potential seizures in the mother.
What is Foetal Alcohol Consumption (FAS)?
A condition caused by excessive maternal alcohol consumption, leading to growth deficiencies & mental impairments.
Which antibiotics are safe during pregnancy?
Penicillins, erythromycin, & cephalosporins.
Which antibiotics should be avoided during pregnancy and when?
Streptomycin, tetracycline family (3rd trimester), & trimethoprim (1st trimester).
What can vitamin A during pregnancy?
Malformation of the ear.