principles of congenital malformations Flashcards
morphogenesis
a form-shaping process in an embryo, controlled by fundamental cell behaviours that result in differential tissue growth.
dysmorphogenesis and birth defects result from
Interference with differential tissue growth in an embryo, that could be occasioned by genetic mutation, teratogen exposure or a combination of these two processes
cellular behaviours involved in morphogenesis include
changes in cell shape, size, position, number, and adhesivity.
what is the norm…
what is most people have, so 2 legs is the norm because most people have 2 legs
what is normogenesis
individuals that develop close to the range of normal - developed normally
structural birth defects involve both
malformations and deformations resulting from abnormal development
Malformations consist of
primary morphologic defects in an organ or body part and result from disturbance of developmental events or processes directly involved in the formation of a particular structure
example of a malformation
NTD - due to non closure of the neural folds or (ancephaly)
malformations can be caused by
environmental (teratogens) and/or genetic factors acting independently or together.
deformations consist of
secondary morphologic defects that are imposed upon an organ or body part due to mechanical forces over a prolonged period – an indirect effect.
example of a deformation
Clubfeet due to compression in the amniotic cavity as a result of insufficient amniotic fluid (Oligohydramnios).
deformations are common with
skeletal system development
most deformations have
very good and excellent prognosis and very low recurrence risk in contrast with many malformations
Disruptions result in
morphological alterations of already formed structures due to destructive processes.
Defects produced by amniotic bands
cleft lip, toe and finger amputations.
examples of malformation syndromes
downs syndrome and foetal alcohol syndrome
what is a syndrome
dysmorphogenesis in one or more tissues due to specific single underlying cause
Down syndrome (Trisomy 21) - symptoms
Flat facial feature with a small nose
Reduced muscle tone (Hypotonia)
Upward/Downward slant to the eye
Enlarge tongue that tends to stick out
Single deep crease across the centre of the palm
Hyperflexibility (extension) of the joints.
ETC
Foetal alcohol syndrome (or Foetal alcohol spectrum disorder - SYMPTOMS
Short palpebral fissure lengths Smooth philtrum Thin upper lip Brain damage ETC
what is teratology?
a term used to describe the study of birth defect or congenital malformation or congenital anomaly.
what is a teratogen?
any factor or agent that causes birth defect or congenital malformation or congenital anomaly
what factors are said to determine the capacity of an agent to produce a birth defect
Genotype of the conceptus and the maternal genome.
Developmental stage at the time of exposure to teratogens.
Dose and duration of exposure to a teratogen.
The mechanism of action of a teratogen is
the specific ways in which it acts on developing cells and tissues to initiate abnormal embryogenesis.
Pathogenesis is
the abnormal developmental processes that result to Dysmorphogenesis.
The mechanisms of teratogens may involve
inhibition of a specific biochemical or molecular process.
Pathogenesis may involve
involve cell death, decreased cell proliferation, or other cellular phenomena.
Manifestations of abnormal development are
death, malformation, growth retardation, and functional disorders.
