Examples of percutaneous delivery include scopolamine, used for treatment of motion sickness, nitroglycerine for angina pectoris and estrogen for postmenopausal symptoms. Melanocytes are cells derived from the neural crest. They migrate early during embryonic development and pass through the dermal mesenchyme to reside in the basal layer of the epidermis. There is approximately one melanocyte for every 10 basal keratinocytes. Unlike keratinocytes, melanocytes rarely divide and normally do not migrate upwards.
Melanocytes have long, dendritic processes that reach the upper and lower layers of the epidermis.
Through these dendrites melanocytes transfer melanosom to the keratinocytes. Melanosomes are melanin-containing organelles that are synthesized by the melanocytes. Dark skin individuals produce more melanosomes and transfer more melanosomes to the keratinocytes. However interestingly, in different races the number of melanocytes is constant for a given cutaneous site. Melanocytes are the cells which give rise to the development of malignant melanoma.