Teratogens Flashcards
what is a teratogen?
agent that can distrub the development of an embryo or fetus”. Teratogens can come in many forms, exposure to teratogens during pregnancy can have a range of effects ranging from very mild to severe, or causing death of the embryo/fetus
what is Wilsons six principles of teratology?
- Susceptibility to teratogenesis depends on the genotype of the conceptus and the manner in which this interacts with adverse environmental factors
- Susceptibility to teratogenesis varies with the developmental stage at the time of exposure to an adverse influence
- Teratogenic agents act in specific ways (mechanisms) on developing cells and tissues to initiated sequences of abnormal developmental events (pathogenesis)
- The access of adverse influences to developing tissues depends on the nature of the influence (agent)
- The four manifestations of abnormal development are death, malformation, growth retardation and functional deficit
- Manifestations of abnormal development increase in frequency and degree as dosage increases, from no effect to totally lethal effect
what is teratology?
study of abnormal development of congenital defects
what are the different types of teratogens?
drugs and chemicals
industrial pollutants
hormones
infectious agents
mechanical factors
what was the mechanism of action of thalidomide?
causes blood vessels in the developing limb to leak and this damaged the developing limb meaning the proximal limb structures failed to develop
what effect do tetracycline (antibiotic) have?
they can cross the placenta and are deposited in the bones and teeth at sites of calcification
-teeth can become discoloured up until the age of 16
-enamel formation is affected
what effect can high doses of streptomycin have (antibiotic)?
inner ear defect
what have recent studies indicated about parcetomal and ibuprofen use in pregnancy?
reduction of germ cell number in future children and grandchildren
what can the epilepsy medication diphenylhydantoin have?
fetal hydatoin syndrome - broad spectrum of craniofacial defects, nail and digital hypoplasia, mental deficiencie
why can the drug methotrexate not be taken in pregnancy?
folic acid inhibitor
-can cause lupus, RA, psoriasis and cancer
-craniofacial abnormalities and development delay
what effect can antineoplastic drugs have (cancer drugs)?
they are highly teratogenic and are designed to kill rapidly dividing cells
what effect can vitamin A have?
(acne treatment)
causes spectrum of deformities related to derivatives of the neural crest, facial structures, outflow tract of the heart and thymus
what teratogen effect can androgen have?
masculinisation of female genitalia (enlarged clitoris and scrotum like structure)
what teratogenic effects can endocrine disruptors have (syntetic oestrogens in the environment)?
responsible for disorders of sexual development
-increased incidence of carcinoma of vagina and cervix
-male offspring increased incidence of testis malformation and abnormal sperm ( no increase of carcinoma of the genital system)
what are the characteristics of FAS?
-facial deformities
-low birth weight
-small head circumference
-development delay
-memory problems
-behavioural problems
poor co-ordination/motor skills
-difficulty in socialisation skills
