Touch Organs in the Hairy and Glabrous Skin of Some Mammals (an Ultrastructural Comparison)

Abstract

Touch organs of the skin in mammals consist of a mechanical transducting component and a sensory component. In the hairy skin, examples of these mechanical transducting components can be seen in the epithelium of hair follicles, and in the hairless skin in the epidermal papillae of the cone skin or the epidermal ridges of the ridges skin. In hairy skin all sinus and guards hairs and most of the vellus hairs are touch organs. The sinus and guard hairs are equiped with Merkel endings, free nerve endings, palisades of lanceolate nerve endings and pilo-Ruffini complexes. The total number of nerve endings varies in guard hairs between 50-200 and between 500-2000 in sinus hairs depending on the size of the follicle. The skin surrounding the body orifices, glabrous skin of the tip of the nose and skin of the finger tips is rich in touch organs. Touch organs of the cone skin known as Eimer organs consist of free nerve endings and of Merkel endings innervating the epidermal cone. Below these cones, the papillary layer shows small lamellated corpuscles and also free nerve endings. In the ridge skin epithelial ridges and crypts, the corresponding dermal papillae, their blood vessels and nervous elements together form the touch organs. In the basal layer of the glandular ridge up to 10 Merkel nerve endings are visible. In young individuals the connective tissue papilla of each crypt shows one Meissner corpuscle and several free nerve endings.