The skin is the largest organ of the body. It acts as a barrier to protect the body from injury, control body temperature and prevent loss of body fluids. The two main layers of the skin are the epidermis and the dermis. Below these is a layer of fatty tissue.
The epidermis is the top, outer layer of the skin. It contains three main kinds of cells:
|Squamous cells||These flat cells are packed tightly together to make up the top layer of skin and form the thickest layer of the epidermis. These cells eventually die and become the surface of the skin. Over time, the body sheds these dead skin cells.|
|Basal cells||These block-like cells make up the lower layer of the epidermis and multiply constantly. As they age, they move up within the epidermis and flatten out to form squamous cells.|
|Melanocytes||These cells sit between the basal cells and produce a dark pigment called melanin, the substance that gives skin its colour. When skin is exposed to ultraviolet (UV) radiation, melanocytes make extra melanin to try to protect the skin from getting burnt. This is what causes skin to tan. Melanocytes are also in non-cancerous (benign) spots on the skin called moles or naevi. Most moles are brown, tan or pink in colour and round in shape.|
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This information is reviewed by
This information was last reviewed January 2021 by the following expert content reviewers: A/Prof Robyn Saw, Surgical Oncologist, Melanoma Institute Australia, The University of Sydney and Royal Prince Alfred Hospital, NSW; Craig Brewer, Consumer; Prof Bryan Burmeister, Radiation Oncologist, GenesisCare Fraser Coast and Hervey Bay Hospital, QLD; Tamara Dawson, Consumer, Melanoma & Skin Cancer Advocacy Network; Prof Georgina Long, Co-Medical Director, Melanoma Institute Australia, and Chair, Melanoma Medical Oncology and Translational Research, Melanoma Institute Australia, The University of Sydney and Royal North Shore Hospital, NSW; A/Prof Alexander Menzies, Medical Oncologist, Melanoma Institute Australia, The University of Sydney, Royal North Shore and Mater Hospitals, NSW; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Paige Preston, Chair, Cancer Council’s National Skin Cancer Committee, Cancer Council Australia; Prof H Peter Soyer, Chair in Dermatology and Director, Dermatology Research Centre, The University of Queensland Diamantina Institute, and Director, Dermatology Department, Princess Alexandra Hospital, QLD; Julie Teraci, Clinical Nurse Consultant and Coordinator, WA Kirkbride Melanoma Advisory Service, WA.