Page 30 -- SKIN STRUCTURE
  
 

The dermis

Beneath the epidermis lies a much thicker skin layer, the dermis. The dermis can be as much as 3000 micrometres thick.
   The dermis is composed largely of the protein collagen. Most of the collagen is organised in bundles running horizontally through the dermis, which are buried in a jelly-like material called the ground substance. Collagen accounts for up to 75% of the weight of the dermis, and is responsible for the resilience and elasticity of the skin.

    

     The ground substance of the dermis, seen under the microscope;      it is an almost unstructured colloidal gel.

The collagen bundles are held together by elastic fibres running through the dermis. These are made of a protein called elastin, and make up less than 5% of the weight of the dermis. Despite their name, they are not involved in the natural elasticity of the skin.

As skin gets older, it loses some of its elasticity and ability to retain water. Collagen production declines as does subcutaneous fat, and the facial muscles start to atrophy.

    

     Massed collagen and elastin fibres in the dermis.

     Both collagen and elastin fibres are made by cells called fibroblasts, which are scattered through the dermis.
   Special substances in the ground substance, called glycoproteins, can hold large amounts of water, and are responsible for maintaining a mass of water in the dermis.
Hyaluronic acid is another important substance that forms part of the tissue that surrounds the collagen and elastin fibres. It has the ability to attract and bind hundreds of times its weight in water. In this way it acts as a natural moisturising ingredient responsible for the skin's plumpness and moisture reserve. As we get older the amount of hyaluronic acid produced in the skin naturally gets less. This is one reason why aging skin becomes less resilient and supple (pliable). Recently