ABSTRACT
The integument (L. integumentum, covering) comprises the skin and its derivatives. Skin and its derivatives cover the entire vertebrate body and form 12-15% of the body weight in the human being. The integument forms the external boundary between the body and the environment. Since the integument is in contact with the external and internal environments it has various structural and functional adaptations that enable it to perform several vital functions at the interphase between these two different environments. The skin offers mechanical and physical protection to the body as it is made of several layers of cells that are continuously being replaced with regeneration of new similar cells. As the vertebrate body is exposed to various pathogens in the external environment, an intact skin offers a barrier to infection. The skin has evolved a highly immune defense system that comprises epidermal Langerhans cells, T-lymphocytes and keratinocytes that are the most distinct cells (Bjerke, 2002).
