Cross section of nail unit with location of culture sampling.  From Lemont H: Clinical criteria and laboratory confirmation of onychomycosis.  Foot Ankle Quarterly 10: 142, 1997.  Reprinted by permission of Foot and Ankle Quarterly.

Posterior nail fold (P) rests on posterior nail plate.  The anterior extension of the fold is eponychium (E).  True cuticle (C) arises from the inferior aspect of the posterior nail fold and adheres to the plate.  NM, nail matrix; NB, nail bed.

The nail bed rests on the nail-bed dermis, which overlies a fatty layer (F) (H&E, ×20).

The nail root (N) is only millimeters away from the base of the distal phalanx (P) (H&E, ×2.5).