What are the main cell types in the epidermis?

The main cell types in the epidermis are keratinocytes, melanocytes, Merkel’s cell, and Langheran’s cells. 

1. Keratinocytes are the primary cell type of the epidermis and are developed in the basal layer. These cells produce keratin and are responsible for the generation of the epidermal water barrier by producing and secreting lipids. Kerinaoctytes also regulate calcium absorption by the activation of cholesterol by UVB light to form vitamin D. 
2. Melanocytes produce the skin pigment, known as melanin. UVB light induces melanin secretion, which is protective against UV radiation. Melanin is produced during the conversion of tyrosine to DOPA through the enzyme tyrosinase. Melanocytes synthesize melanins and then are processed in keratinocytes to achieve skin pigmentation. 
3. Langherans cells are first line defenders from substances getting into the skin and have a significant role in antigen presentation. Langerhans cells are derived from CD34 positive stem cells of bone marrow and exist in the mononuclear phagocytic system. These cells express MHC I and MHC II molecules, uptake antigens in the skin and transport to the lymph node. 
4. Merkel cells are found in the stratum basale, and serve as mechanoreceptors for light touch. They are primarily found in fingertips, but are also found in the soles, palms, and oral mucosa. Merkel cells are bound to keratinocytes by desmosomes and their membranes interact with free nerve endings in the skin.