Normal Functions of the Skin

Epidermis
The epidermis' main function is to provide a protective external covering. The epidermis' tissues are avascular and are composed of stratified, squamous epithelial cells. The deeper cells in this layer produce the skin's colour pigments. The deepest layer renews the skin every 10 - 15 days, as it migrates to the surface of the skin.

Dermis
The dermis is a fibro-elastic layer that contains blood vessels, lymphatic vessels and most of the sensory nerve endings. It also contains the base structures that eventually open onto the epidermis, including the hair follicles, sebaceous and sweat glands. In the dermis, the blood vessels are thin-walled and readily susceptible to damage from pressure. However, they tend to lie vertical to the skin surface. This positioning allows them to withstand pressure damage to a larger degree than those in the subcutaneous layer that lie parallel to the underlying bone and muscle.

Subcutaneous Tissue
The subcutaneous tissue (or hypodermis) layer is the last layer of protection for the fascia, muscles and bone. It is composed of adipose (fatty) tissues and also contains blood vessels. Underneath this layer is the fascia. Fascia separates skin from the muscles and bones.

Skin is the largest organ of the body. Normal functions include:

• sensation and perception
• thermoregulation
• protection
• prevention of water loss
• excretion and secretion
• synthesis of Vitamin D.

As you can see within the picture of the skin cross-section, skin is comprised of three primary layers. Click on each of the skin layers in the picture for more information. These three layers are not an even thickness throughout the body. The skin thickness varies from 0.5 - 3mm, with the thickest skin being on the palms of hands and soles of feet. In general, the thicker the skin, the greater the ability to tolerate the effects of pressure.

Take a moment to compare the thickness and texture of the skin on your abdomen with skin on the sole of your foot.

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