Chapter 12 Common integument
The term common integument refers to the outer covering of the body. It is said to be the largest organ of the body and, because it has a variety of component parts, it has a range of functions. The integument includes:
The skin covers the external surface of the body, forming a complete barrier against the external environment. It is perforated by various natural openings, e.g. the mouth and the anus, and at these points it blends with the mucous membranes lining the openings. The functions of the skin are:
The skin is composed of two layers: the epidermis or superficial layer and the underlying dermis (Fig. 12.1). The hypodermis lies beneath the skin.
The epidermis is composed of stratified squamous epithelium and has multiple layers of cells that are continually renewed. New cells are produced in the deepest layers of the epidermis and are pushed upwards to the surface as a result of mitosis below (see Ch. 1). The surface cells are continually lost and these dead cells or squames are seen as scurf in the animal’s coat. This process replaces the cells that are lost due to friction and wear. The layers, or strata, of the epidermis are, from deep to superficial:
The colour of the skin and overlying hair may not necessarily be the same and this may be noticed when clipping an area for a surgical operation. It is interesting to note that the skin of polar bears is black but the fur is white!