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Skin Facts

The skin is the largest organ of the body. The skin serves our body in two major life-preserving functions: protection against infection and prevention of loss of body fluids. In a burn patient, these functions are diminished or eliminated. The skin also functions as a temperature control and regulates the loss of heat from the body.

In third-degree burns (full thickness), all of the skin layers are destroyed. Regeneration of the skin is not possible and these wounds must be covered because the body has lost the ability for new skin to grow in these areas. Most partial thickness burn wounds (first- and second-degree burns) will heal on their own.

The skin is composed of the following layers, with each layer performing specific functions.

Epidermis

The epidermis is the thin outer layer of the skin which consists of the following three parts:

• Stratum Corneum (horny layer) - This layer of fully mature keratinocytes which contain fibrous proteins (keratins). The outermost layer is continuously shed. The stratum corneum prevents the entry of most foreign substances as well as the loss of fluid from the body.
  
• Keratinocytes (squamous cells) - This layer, just beneath the stratum corneum, contains living keratinocytes, which mature and form the stratum corneum.
  
• Basal Layer - The basal layer is the deepest layer of the epidermis, containing basal cells. Basal cells continually divide, forming new keratinocytes, replacing the old ones that are shed from the skin's surface.
  

The epidermis also contains melanocytes, which are cells that produce melanin (skin pigment).

Dermis

The dermis is the middle layer of the skin. The dermis contains the following:

• blood vessels
  
• lymph vessels
  
• hair follicles
  
• sweat glands
  
• collagen bundles
  
• fibroblasts
  
• nerves
  

The dermis is held together by a protein called collagen, made by fibroblasts. This layer also contains pain and touch receptors.

Subcutis

The subcutis is the deepest layer of skin. The subcutis, consisting of a network of collagen and fat cells, helps conserve the body's heat and protects the body from injury by acting as a "shock absorber."

In addition to serving as a protective shield against heat, light, injury, and infection, the skin also:

• regulates body temperature.
  
• stores water and fat.
  
• is a sensory organ.
  
• prevents water loss.
• prevents entry of bacteria.