Merkel cell
Epidermis · Basal layer CK20 Slowly adapting type I
Keratinocyte-lineage neuroendocrine cell in the stratum basale, coupled to a myelinated A-beta afferent to form the slowly adapting type I mechanoreceptor that encodes sustained pressure, edges and texture.
Detail
- Location
- Basal layer, concentrated at fingertips, lips and around hair follicles
- Receptor type
- Slowly adapting type I; small receptive field, high spatial resolution, so it underlies two-point discrimination and Braille reading
- Markers
- Cytokeratin 20 positive, with dense-core neurosecretory granules and synapse-like contact with the afferent terminal
- Contrast
- Meissner corpuscles are rapidly adapting type I (flutter), Pacinian rapidly adapting type II (vibration), Ruffini endings slowly adapting type II (skin stretch)
When it goes wrong
Merkel cell polyomavirus integration or UV damage in elderly or immunosuppressed skin
Merkel cell carcinoma: a rapidly growing painless nodule on sun-exposed head, neck or limb, CK20 positive, with a far higher mortality than melanoma stage for stage
Practise this structure
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