Paucity of presumptive ruffini corpuscles in the index finger pad of humans.

Abstract

Classically recognized as the cutaneous stretch receptors associated with the slowly adapting type II (SAII) primary afferents, Ruffini corpuscles have rarely been reported in the skin, despite numerous histologic investigations. Electrophysiological recordings of the primary afferents in humans suggest that SAII fibers represent approximately 15% of the myelinated mechanosensitive axons in the peripheral nerves innervating the volar surface of the hand. In the present study, an analysis of glabrous skin was conducted in human donors to assess the distribution of Ruffini and Ruffini-like corpuscles in the distal phalanx of the index finger. Only one presumptive Ruffini corpuscle was found in the skin processed for double immunofluorescence labeling with antibodies against protein gene product 9.5 and neurofilament 200-kDa subunit. Based on their relatively scattered distributions, we conclude that very few SAII primary afferents are likely to terminate as Ruffini corpuscles in human glabrous skin.