The skin
About the skin and skin cells
The skin is the largest organ in the body. It:
- protects the body from injury and infection
- protects the body from ultraviolet light (UV light) by producing melanin – this is the pigment that gives skin its colour
- keeps bacteria or viruses from getting into the blood and causing infections
- keeps fluids and proteins in the body
- helps to control body temperature
- gives us our sense of touch, through nerve endings –this is how we can feel and react to pain, heat or pressure
- helps the body make vitamin D when exposed to the sun – this is important to keep our bones healthy.
- provides the skin with its colour.
Related pages
Layers of the skin
The skin is divided into 2 main layers. The surface layer is the epidermis. The layer underneath is the dermis. Below these layers is a deeper layer of fatty tissue.
The epidermis
This is the thin outer layer of the skin. The epidermis contains 3 types of cell:
- Squamous cells – these are flat cells on the surface of the skin that are always shedding to make way for newer cells.
- Basal cells – these are rounder cells that are found under the squamous cells.
- Melanocytes – these are found between the basal cells. They make a pigment called melanin. This gives skin its colour and protects it from UV light.
The dermis
This is the inner layer of skin and is much thicker than the epidermis. It contains nerve endings, blood vessels, sweat glands and lymphatic vessels. It provides the epidermis with nutrition.
The hypodermis (fatty layer)
This is the fatty layer. It is the supportive layer of the skin and protects the body against cold. There are blood vessels and nerves in the hypodermis.
Structure of the skin
Melanocytes
Melanocytes are cells that make a pigment called melanin. Melanin gives our skin, hair and eyes their colour. It also protects skin from the harmful effects of the sun. Moles are a group or cluster of melanocytes that are close together. They are sometimes called naevi.
When skin is exposed to sunlight, the melanocytes make more melanin. This is to absorb more of the harmful UV rays from the sun. This makes the skin look darker, or suntanned. A suntan is a sign that the skin is trying to protect itself.
If you have black or brown skin, you have the same number of melanocytes as people with white skin. But your melanocytes make more melanin. This means you have more natural protection from UV rays. You can still get skin cancer, but it is less likely. You still need to protect your skin from the sun and check for anything unusual.
About our information
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References
Below is a sample of the sources used in our skin cancer information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk
Keohane SG, Botting J, Budny PG, et al. British Association of Dermatologists guidelines for the management of people with cutaneous squamous cell carcinoma 2020. The British Journal of Dermatology. 2021;184(3): 401–414. Available from www.doi.org/10.1111/bjd.19621 [accessed May 2024].
Nasr I, McGrath EJ, Harwood CA, et al. British Association of Dermatologists guidelines for the management of adults with basal cell carcinoma 2021. The British Journal of Dermatology. 2021;185(5): 899–920. Available from www.doi.org/10.1111/bjd.20524 [accessed May 2024].
Sharma A, Birnie AJ, Bordea C, et al. British Association of Dermatologists guidelines for the management of people with cutaneous squamous cell carcinoma in situ (Bowen disease) 2022. The British Journal of Dermatology. 2023;188(2): 186–194. Available from: www.doi.org/10.1093/bjd/ljac042 [accessed May 2024].
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Reviewers
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Professor Samra Turajlic, Consultant Medical Oncologist.
With thanks to: Dr Stephanie Arnold, Consultant; Kerry Jane Bate, Advanced Nurse Practitioner; Dr Philippa Closier, Clinical Oncologist; Sharon Cowell-Smith, Macmillan Advanced Nurse Practitioner Skin Cancers; and Dr Benjamin Shum, Medical Oncologist.
Thanks also to the other professionals and people affected by cancer who reviewed this edition, and to those who shared their stories.
Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.
The language we use
We want everyone affected by cancer to feel our information is written for them.
We want our information to be as clear as possible. To do this, we try to:
- use plain English
- explain medical words
- use short sentences
- use illustrations to explain text
- structure the information clearly
- make sure important points are clear.
We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.
You can read more about how we produce our information here.
Date reviewed
Our cancer information meets the PIF TICK quality mark.
This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.
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