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Development of Limbs (4th to 8th Week)
Chronology of Limb Development
4 stages of Limb Development
1.) Initiation
limb bud formation
2.) Specification of limb pattern
growth of the 3 axis occurs
3.) Tissue formation and limb morphogenesis
limb elements form
4.) Growth
occurs into early adulthood
Migration of Lateral Plate Mesoderm
SEM of Limb Bud from a Day 29 Embryo
Normal Chick Limb Anatomy
Role of Apical Ectodermal Ridge and
Mesodermal Core in Limb Bud Development
Formation of Supernumerary Limbs
Meromelia
The Generation of Limbless Vertebrates
Snake Axial Skeleton
Formation of Snake Hindlimb
Is regeneration of limbs possible?
Newt Limb Regeneration
This is a time-lapse sequence showing
the stages of newt limb regeneration.
The surgical amputation was at the
level of the humerus. The pictures
show the wound-healing,
de-differentiation, blastema and
re-differentiation stages of
regeneration. Total time shown is
approximately 20-25 days.
Patterning of the Antero-Posterior Axis:
Transplantiaton of ZPA
Evidence for a Morphological Gradient
Established by the ZPA
Retinoic Acid Transplantation Experiment
Retinoic acid induces mirror polydactyly
Whole mount of chick embryo showing
expression of Sonic Hedgehog
Polydactyly showing partial duplication of the
right foot and toes
Establishment of the Dorso-Ventral Axis
Forelimb versus Hindlimb Signals
Time Course of Upper and Lower Limb
Development
Formation of the Hand
Webbed Hand (Syndactyly)
Nucleoli Differences in Chick and Quail
Chick
Quail
Quail-chick Cell Tracing Experiment
Limb Musculature Develops from Ventral and
Dorsal Condensations of Somitic Mesoderm
Dorsal Muscle Mass
extensors and supinators upper limb
extensors and abductors lower limb
Ventral Muscle Mass
flexors and pronators upper limb
flexors and adductors lower limb
Bone Development
X-rays of Bone Growth
Cogenital Anomalies of Limb
1.) Reduction defects
Meromelia
Amelia
2.) Duplication defects
Polydactyly
3.) Dysplasia
Syndactyly
Gigantism
Critical Periods in Human Prenatal
Development
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