ABSTRACT
The nail plate lies on the nail bed, is produced by the nail matrix, and is framed and ensheathed by the nail folds and the hyponychium (Figure 1.1). All these components, that is, nail plate, nail bed, nail folds, matrix, and hyponychium, make up the nail unit (Gonzalez-Serva 1997) and are described below. The nail unit starts to develop in the tenth week of embryogenesis and is almost completely formed by the 17th week, after which changes in the nail unit are mainly associated with growth; it is well perfused by blood and lymphatic vessels, has a rich nerve supply, and is anchored in place by attachment to the distal phalanx (Dawber et al. 2001; Fleckman 2005; de Berker et al. 2007; de Berker and Forslind 2004; Zaias 1990).
