Embryology Flashcards
Week 4
Heart begins to beat
Formation of limbs
Week 5
Development of face, limbs, eye, kidney, umbilical cord
Separation of heart
Development of digestive organs
Facial cleft/ limb anomalies/ cardiac wall defects
Week 6
Spontaneous embryonic movement
Development of ear
Week 7
Formation of AV valves
Ossification begins
Embryo surrounded by amniotic sac
Skeletal/ cardiac valve defects/ cleft palate/ kidney anomalies
Malformation
Morphological defect of an organ/ larger body region
Intrinsically abnormal development process
Mechanism unknown - can be due to anomalies in cell differentiation, migration, proliferation + death.
Deformation
Abnormal shape/ body part due to mechanical forces.
Usually over prolonged period of time, can be reversed.
Disruption
Morphological defect of an organ/ body part resulting from external breakdown or interference with normal development process.
E.g. infections, drugs, amniotic band rupture, hyperthermia, ionising radiation.
Dysplasia
Abnormal organisation of cells in tissues + its morphological results
E.g. Marfan’s syndrome, congenital ectodermal dysplasia.
Sequence
Cascade of events arising from single known or presumed structural defect
Pierre Robin sequence
Jaw constraint - micrognathia - glossoptosis - U-shaped cleft palate
Syndrome
multiple defects that occur together in a predictable way.
Thought to be pathogenetically related.
Polytopic field defect
Multiple anomalies in same developmental region
Arises from disturbance of single developmental field.
Association
Non-random, pathogenically unrelated, multiple defects. Need to be present in more than 2 individuals with statistically related symptoms.
Embryology
Study of prenatal development of embryos + fetuses
Embryogenesis
From fertilisation to end of week 8
Fetal period
From week 9 to birth
Teratology
Studies developmental anomalies, birth defects + their causes
Teratogen
Any agent that causes an abnormality following fetal exposure during pregnancy
Polytopic field
group of anomalies derived from the disturbance of a single developmental field
Acheiria, apodia acheiropodia
Absence of hands, feet or both
Adactyly
Absence of all digits on limb
Amelia, ectromelia
Complete absence of one or more limbs
Arachnodactyly
Elongated digits
Brachydactyly
shortened digits
Camptodactyly
Flexion contracture of finger which cannot be fully extended
Clinodactyly
Curving of 5th finger towards 4th
Hemimelia
Absence of pre or postaxial structures of a limb
Meromelia
Absence of part of a limb
Oligodactyly
Absence of any numbers of fingers or toes
Phocomelia
Abence of proximal limb structures
Polydactyly
Presence of extra digits or part of digits
Slit hand/ foot
Absence of central components of hand or foot
Syndactyly
Fusion of digits
Syntosis
Fusion of bones or intervening soft tissue
Triphalangeal thumb
thumb with 3 instead of 2 phalanges.
