Merkel's discs

Merkel nerve endings are mechanoreceptors, a type of sensory receptor, that are found in the basal epidermis and hair follicles. They are classified as slowly adapting type I mechanoreceptors. They are large, myelinated nerve endings. They provide information on pressure, position, and deep static touch features such as shapes and edges.

Merkel cells in the basal epidermis of the skin store neuropeptides which they release to associated nerve endings in response to pressure. In burns, Merkel endings are most commonly lost.

Each ending consists of a Merkel cell in close apposition with an enlarged nerve terminal. This is sometimes referred to as a Merkel cell–neurite complex, or a Merkel disk receptor. A single afferent nerve fibre branches to innervate up to 90 such endings.

In mammals, Merkel nerve endings have a wide distribution. Merkel nerve endings are found in the basal layer of glabrous and hairy skin, in hair follicles, and in oral and anal mucosa. In humans, Merkel cells (along with Meissner's corpuscles) occur in the superficial skin layers, and are found clustered beneath the ridges of the fingertips that make up fingerprints. In hairy skin, Merkel nerve endings are clustered into specialized epithelial structures called "touch domes" or "hair disks". (Some other types of mechanoreceptors, such as Pacinian corpuscles and Ruffini endings, are found primarily in subcutaneous tissue.) Merkel receptors are also located in the mammary glands. Wherever they are found, the epithelium is arranged to optimize the transfer of pressure to the ending.

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