Do other types of cells normally occur in the epidermis?

In addition to keratinocytes, three other cells are normally found in the epidermis. The melanocyte, the most common, is a dendritic cell situated in the basal cell layer. There are approximately 36 keratinocytes for each melanocyte. This cell’s function is to synthesize and secrete melanin-containing organelles called melanosomes.

The next most common cell is the Langerhans cell, which is a bone marrow–derived, antigen-presenting cell that has very important immune surveillance functions. On light microscopy, these dendritic cells are primarily distributed in the stratum spinosum. Langerhans cells were first described by Paul Langerhans in 1868 while he was still a medical student. Also located in the epidermis in small numbers are Merkel cells. The function of these cells is not fully established, but they are frequently in contact with nerve fibrils. Ultrastructurally, Merkel cells contain electron-dense bodies that  are also found in APUD (amino acid precursor uptake and decarboxylation) cells of endocrine glands.