Sensory nerve endings in the human female umbilical skin: light and electron microscopic study

ABSTRACT

Sensory innervation consists of free nerve endings and endings terminated with corpuscular structures. Cutaneous innervation is closely associated with major skin functions such as wound healing, thermoregulation, and hair growth. Diminution in erotic sensation has been reported by some women after abdominal lipectomy. Hence, the lack of knowledge about the normal sensory distribution in the umbilical skin has been a problem. The purpose of this study was, therefore, to map the sensory innervation of the human umbilical skin using histological, immunohistochemical [S-100 protein], and ultrastructural techniques. Umbilical skin biopsies were obtained during surgical procedures for abdominal lipectomy in female participants. The specimens were processed for light and electron microscopic examinations. With light microscopy, abundant Meissner's, Ruffini, and innervated Merkel cells were observed. Numerous free nerve endings, comparable with those observed in male and female external genitalia, were observed surrounding the ducts and the acini of sweat glands. Pacinian corpuscles were also observed, but less frequently. Neurovascular bundles, closely related to those observed in female external genitalia, were also observed. The relatively dense sensory innervation in the umbilical skin that was comparable with that in lip, as well as in male and female external genitalia, can be correlated with the observed retardation in the erotic sensation in clinical studies after removal of a part of the umbilical skin. The frequently observed innervated Merkel cells and the widely scattered Meissner's corpuscles in the umbilical skin could explain the relatively high tactile sensation in this skin