Skin, like all tissues, is made out of multiple cells attached together to serve a common function.  Thus, there can be a variety of different cells residing within the same tissue.

1 minute video of normal skin anatomy

Skin is divided into 3 major layers:  the epidermis, dermis, and hypodermis.  This chapter will focus predominantly in the epidermal layer as this is where melanocytes reside.

^{1 Minute Video of Normal Skin Anatomy by Lyz Boyd, licensed under All Rights Reserved}

Normal skin histology

Presented by  Lyz Boyd using a histology slide of H&E stained normal skin  (DHPLC e-slide: PATH 304-004)

^{1 Minute Video of Normal Skin Histology by Lyz Boyd, licensed under All Rights Reserved}

Section Summary

• The skin has three layers: the epidermis, dermis & hypodermis (subcutaneous).
• The epidermis is the most exposed layer, comprised mostly of keratinocytes and a minor amount of melanocytes.  Keratinocytes are filled with the tough protein keratin, which helps the epidermis be durable.  The most exposed layer of the epidermis are layers of dead, keratin-filled keratinocytes histologically evident by its lack of nuclei and strong staining for protein.
• Melanocytes reside in the epidermis on the regenerative layer (i.e. stratum basale).  Melanocytes continually produce the protein pigment melanin which provides a physical barrier near the nuclei of living keratinocytes, thus protecting the DNA from UV damage.  When the keratinocytes die at the most-exposed layer, the melanin pigment has already degraded as there is no longer any need to protect living nuclei. Thus, the most exposed layer of the skin lacks pigment.
• The thicker dermal & epidermal layers contain large vessels and nerves which help supply the epidermis with nutrients and sensation.

Review questions