Genetic Research of Hand Congenital Deformities and Advancement in Plastic and Reconstructive Treatment

Limb bud is composed of mesodermal mesenchyma or mesodermal center and one layer of dermal layer on the external surface, and it is the initial phase of upper limb development. The development of limb bud is the result of gradual changes of various signaling molecular mechanisms in three-dimensional space, and the three axes are proximo-distal, anteroposterior, and dorsoventral, which correspond to the shoulder-finger direction, thumb-little finger direction, and forearm-palm direction in limb morphology. In order to guarantee the correct development and growth of limb bud, three categories of cell groups are of vital importance: they are apical ectodermal ridge (AER) at the lateral side of the limb bud, the progress zone (PZ) at the medial side of the limb bud, and the zone of polarizing activity (ZPA) at the posterior side of the limb bud. The signaling molecules generated by the cells in these regions decide the growth directions of the adjacent cells so that the normal growth and development of upper limb is maintained (Fig. 15.1).