Covers teratology and the factors that make an embryo vulnerable to malformation, including genotype, developmental stage, dose and duration of exposure, and critical periods. It sets out the causes of birth defects with approximate percentages, then lists genetic, infectious, physical, chemical and maternal teratogens with the anomalies each is linked to, including a table-like run of chromosomal syndromes. It defines malformation, disruption, deformation, syndrome and association, and closes with monozygotic, conjoined and dizygotic twinning.
Topic 59 of 59 in the MU Pleven syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 8 sections, about 539 words (4 min of reading), with 30 flashcards.
In this note
Topic 59- Teratology – teratogenic factors. Twins
Teratology and Birth Defects
Principles of Teratology
Causes of Birth Defects
Teratogenic Factors
Teratogenic Agents
Phases of Teratogenesis
Twins
Teratology and Birth Defects
Definition:
Teratology is the study of abnormalities in the natural world, both real and imagined.
Teratogenesis refers to the formation of congenital malformations or fetal monstrosities.
Principles of Teratology
Susceptibility to teratogenesis depends on:
Genotype of the conceptus and maternal genome.
Developmental stage at the time of exposure.
Teratogens act in specific ways on developing cells and tissues.
Manifestations of abnormal development include:
Death, malformation,
growth retardation, and
functional disorder.
Manifestations depend on dose and duration of exposure to a teratogen.
Embryonic structures are susceptible only during specific critical periods corresponding to active differentiation and morphogenesis.
Susceptibility varies with genotype; gene-environment interactions differ between embryos.
Dose-response relationship: lowest dose may have no effect; highest dose may be lethal.
