Teratology
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It is the study of abnormal development.
It is the branch of science that studies the causes,
mechanisms, and patterns of abnormal development.
What do you mean by
congenital anomaly?
Ans: it is a structural abnormality of any type that is
present at birth.
There are four clinically significance types of anomalies
a) malformation :
occurred during organogenesis
caused by
environmental & / or genetics
b) Disruption:
morphological alteration of already form structures due to destructive
processes . Example: amniotic bands
c) Deformation :
mechanical forces that mold a part of fetus. Example: clubfoot
d) Dysplasia:
abnormal organization of cells. Example: congenital ectodermal Dysplasia
The causes of birth
defects or congenital anomalies are ;;;
1. genetic factors such as chromosome
abnormalities
2. environmental factors such as drugs
and viruses
3. multifactorial inheritance (both genetic
and environmental factors)
- Genetic factors such as
chromosome abnormalities: they are two types
a) Numerical :i) trisomy – Down syndrome
( extra 21 chromosome ) Klinefelter syndrome (47XXY) ii) monosomy: Turner
syndrome (45X)
b) Structural abnormality: Prader willi
syndrome, Cri-du-chat syndrome
- Environmental factors :
a) Infectious agents: i) Rubella virus :
Cataracts, heart defects ii) HIV : growth retardation
b) Physical agents: X-rays: spina
bifida, cleft palate
c) Chemical agents: i)Smoking: growth
retardation ii) alcohol : fetal alcoholic syndrome, mental retardation iii)
thalidomide : limbs defects
d) Hormones: maternal diabetes: heart
& neural tube defects
- Multifactorial inheritance (both
genetic and environmental factors)
Cleft lip, neural tube defects etc.
Principles of Teratology: ( capacity of an agent to produce birth
defects)
- Susceptibility
- to
teratogenesis depends on the genotype of the conceptus
- Susceptibility
to teratogens varies with the developmental stage at the time of exposure
- Manifestations
of abnormal development depend on
dose and duration of exposure to a teratogen
- Teratogens
act in specific ways on developing cells to initiate abnormal
embryogenesis
- Manifestations
of abnormal development are death, malformation, growth retardation &
functional disorders
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