In embryology, the limb bud is a structure formed by the developing limb, derived from lateral plate mesodermcitation needed. It is intimately related with the apical ectodermal ridge, which secretes factors (fibroblast growth factors for example) inducing the initial differentiation of the limb bud. In turn, the mesodermal tissue of the limb bud secretes factors sustaining the development of the Apical Ectodermal Ridge.
