Function 

The skin is the largest organ of the body, making up 16% of body weight, or up to 2.7 Kg in the average adult (10). It has many vital functions, including; immune function, homeostasis, sensation, a protective barrier to mechanical, thermal, physical and chemical injury. It also reduces the harmful effects of UV radiation, prevents moisture loss and is involved in vitamin production. It is a dynamic organ in a constant state of change; cells of the outer layers continuously shed and are replaced by inner cells moving to the surface (11, 12).

Structure 

The skin is composed of the epidermis and dermis with a complex nerve and blood supply. A third layer, the hypodermis, is composed of mainly fat and a layer of loose connective tissue. These layers play critical roles in protecting the body from any mechanical damage such as wounding. The epidermis is thin and completely cellular, but has sufficient thickness to function as a barrier. Mammalian epidermis and its appendages (hair, nail, sweat and sebaceous glands) maintain homeostasis by constant recycling of the basal cell layer. The epidermis is also exposed to ultraviolet radiation, and the resulting damage is one of the factors contributing to the constant sloughing of cells from the stratum corneum, which are replaced by migrating cells from the basal layers (13).

 

The dermis, situated directly below the epidermis makes up the bulk of the skin and is composed of collagen with some elastin and glycosaminoglycans (GAGs). The main cell type present are fibroblasts, capable of producing remodelling enzymes such as proteases and collagenases, which have critical roles in wound healing. The hypodermis is the layer beneath the dermis and contains a considerable amount of adipose (body fat) tissue that is well vascularized and contributes to both the mechanical and thermoregulatory properties of the skin (13).