Identification of the Ruffini corpuscle in human hairy skin.

A Ruffini corpuscle was identified in the dense reticular dermis of the human scalp from a patient with alopecia areata. The corpuscle measured approximately 50 micrometer in diameter. One afferent myelinated axon with a diameter of 4-6 micrometer supplies the corpuscle. Branched axon terminals and the associated Schwann cells tightly envelop parallel bundles of collagen fibrils. Axon terminals evidenced focal swellings, and small finger-like protrusions projected into the endoneural connective tissue. The terminals are characterized by the presence of abundant mitochondria, numerous vesicles, particles of glycogen and electron-opaque lipid material. A thin perineural capsule envelops the bundles of collagen fibrils and associated terminals. The present study provides the first electron-microscopic characterization of a Ruffini corpuscle in human hairy skin.