eponychium

1. The thin, condensed, eleidin-rich layer of epidermis that precedes and initially covers the nail plate in the embryo. It normally degenerates by the eighth month except at the nail base where it remains as the cuticle of the nail. 2. [NA] The corneal layer of epidermis overlapping and in direct contact with the nail root proximally or the sides of the nail plate laterally, forming the undersurface of the nail wall or nail folds. SYN: hidden nail skin, perionychium. 3. The thin skin adherent to the nail at its proximal portion. SYN: epionychium. [G. epi, upon, + onyx (onych-), nail]

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ep·o·nych·i·um .ep-ə-'nik-ē-əm n

1) the thickened layer of epidermal tissue over the developing fetal fingernail or toenail that disappears before birth except over the base of the nail where it persists as the perionychium

2) the quick of a nail

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n.

see nail

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ep·o·nych·i·um (ep″o-nikґe-əm) [epi- + onyx] 1. [TA] the narrow band of epidermis that extends from the nail wall onto the nail surface; called also cuticle and perionychium. 2. the horny fetal epidermis at the site of the future nail.