Dermatology: Cellular Composition of the Epidermis
The epidermis is more than just keratin; it is a highly specialized immune and pigment-producing environment.
| Cell Type | Function & Characteristics |
|---|---|
| Keratinocytes | Main structural cells produce keratin. Migrate from basal layer to cornified layer (approx. 28-day cycle). |
| Melanocytes | Located in the basal layer; produce melanin (UV protection). Derived from Neural Crest. |
| Langerhans Cells | Dendritic cells in the stratum spinosum are “sentinel” immune cells that present antigens to T-cells. |
| Merkel Cells | Located in the basal layer, mechanoreceptors for light touch sensation. |
High-Yield Exam Pearl:
- Melanocytes: Remember that all people have roughly the same number of melanocytes; skin color differences are due to melanin production rate and dispersion, not cell count.
- Langerhans Cells: These are the classic “Antigen Presenting Cells” (APCs) of the skin; watch for their involvement in conditions like Histiocytosis.
- Merkel Cells: High clinical importance because they are the origin of Merkel cell carcinoma—an aggressive neuroendocrine skin cancer.