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The skin

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 dermis. Below these is a layer of fatty tissue.

Epidermis

This is the top, outer layer of the skin. It is made up of several cell types:

Squamous cells – These flat cells are packed tightly together to make up the top layer of skin. They form the thickest layer of the epidermis.

Basal cells – These block-like cells make up the lower layer of the epidermis. The body makes new basal cells all the time. As they age, they move up into 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 damaged by ultraviolet (UV) radiation, melanocytes make extra melanin. Melanocytes are also found in non-cancerous spots on the skin called moles or naevi.

Dermis

This layer of the skin sits below the epidermis. The dermis contains the roots of hairs (follicles), sweat glands, blood vessels, lymph vessels and nerves. All of these are held in place by collagen and elastin, the proteins that give skin its strength and elasticity.

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This information is reviewed by

This information was last reviewed in January 2020 by the following expert content reviewers: Prof Diona Damian, Dermatologist, The University of Sydney at Royal Prince Alfred Hospital, and Associate, Melanoma Institute of Australia, NSW; Dr Annie Ho, Radiation Oncologist, Genesis Care, Macquarie University, St Vincent’s and Mater Hospitals, NSW; Rebecca Johnson, Clinical Nurse Consultant, Melanoma Institute of Australia, NSW; Shannon Jones, SunSmart Health Professionals Coordinator, Cancer Council Victoria; Liz King, Skin Cancer Prevention Manager, Cancer Council NSW; Roslyn McCulloch, Consumer; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Paige Preston, Policy Advisor, Cancer Prevention, Health and Wellbeing, Cancer Council Queensland; Dr Michael Wagels, Plastic and Reconstructive Surgeon, Princess Alexandra Hospital, QLD. Thanks also to Sydney Melanoma Diagnostic Centre for providing the dysplastic naevus photograph, and to Prof H Peter Soyer for providing the other photographs. We also thank the health professionals, consumers and editorial teams who have worked on previous editions of this title.