Introduction to limb development and evolution in tetrapod vertebrates

This first lesson defines the general scope and objectives of the lecture. It uses the system of embryonic limb development and evolution to demonstrate the extent to which a multidisciplinary approach combining classical embryology, human genetics and recent advances in molecular biology and genomics can shed light on the intimate mechanisms whose disturbances are at the root of many congenital anomalies. This is followed by a general introduction to limb development and its particular epistemic value as a model system in experimental embryology for over 60 years, noting in particular its great adaptive flexibility, despite having to cope with unavoidable constructional constraints. This is followed by a discussion of the positioning of the limbs on the embryo's body axis and the initiation of their growth.