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Skin explained

The skin is the largest organ of the human body. It is soft, to allow movement, but still tough enough to resist breaking or tearing. It varies in texture and thickness from one part of the body to the next. For instance, the skin on the lips and eyelids is very thin and delicate, while skin on the soles of the feet is thicker and harder. The skin is a good indicator of general health. If someone is sick, it often shows in their skin.

A range of functions
Skin is one of our most versatile organs. Some of the different functions of skin include:

  • A waterproof wrapping for the entire body
  • The first line of defence against bacteria and other organisms
  • A cooling system via sweat
  • A sense organ that gives us information about pain, pleasure, temperature and pressure.
The epidermis
The skin you can see is called the epidermis. This protects the more delicate inner layers. The epidermis is made up of several ‘sheets’ of cells. The bottom sheet is where new epidermal cells are made. As old, dead skin cells are sloughed off the surface, new ones are pushed up to replace them. The epidermis also contains melanin, the pigment that gives skin its colour.

The dermis
Underneath the epidermis is the dermis. This is made up of elastic fibres (elastin) for suppleness and protein fibres (collagen) for strength. The dermis contains sweat glands, sebaceous glands, hair follicles, blood vessels and nerves.

Glands and blood vessels
The dermis is well supplied with blood vessels. In hot weather or after exercise, these blood vessels expand, bringing body heat to the skin surface. Perspiration floods out of sweat glands and evaporates from the skin, taking the heat along with it. If the temperature is cold, these blood vessels in the dermis contract, which helps to cut down on heat loss. Sebaceous glands in the dermis secrete sebum to lubricate the skin.

Hair and nails
Our lack of a complete cover of body hair makes human skin very different from the skin of any other animal. Hair is made up of a protein called keratin. The amount of hair on the body varies from place to place. Hairless sites include the lips, palms and soles of the feet. The hairiest sites include the scalp, pubis and underarms in both sexes, and the face and throat in men. Nails are made from skin cells but the only live parts are the nail bed and the nail matrix just behind the cuticle. The nail itself is made of dead cells.

Nerves
Both the dermis and epidermis have nerve endings. These transmit information on temperature, sensation (pleasure or pain) and pressure. Some areas have more of these nerves than others, like the fingertips for example.

Common problems
Some common skin problems include:
  • Acne - caused by hormones
  • Dermatitis - inflammation of the skin, with many different triggers
  • Fungal infections - like tinea (athlete’s foot)
  • Skin cancer - from long term exposure to the sun’s UV rays
  • Sunburn - a radiation burn from the sun’s UV rays
  • Warts - caused by a virus.
Where to get help
  • Your doctor
  • Dermatologist
Things to remember
  • Skin is the largest organ of the body.
  • It is made up of two main layers, the epidermis and the dermis.
  • Skin is a good indicator of general health.
    Better Health Channel - Related Quiz.

    Related articles:

Acne.
Ageing - the skin.
Birthmarks.
Boils.
Cellulitis.
Cradle cap.
Eczema - coping tips.
Eczema explained.
Eczema treatments.
Erythema nodosum.
Frostbite.
Molluscum contagiosum.
Pityriasis rosea.
Pressure sores.
Psoriasis explained.


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St Vincent's Hospital Melbourne

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Article publication date: 13/10/1999
Last reviewed: 31/03/2004

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This article, like all health articles on the Disability Online, is sourced from Better Health Channel and has passed through a rigorous and exhaustive approval process. It is also regularly updated. For more information see Better Health Channel quality assurance page.


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