ABSTRACT
Anatomy The skin of dogs and cats is quite different from human skin. Skin thickness, hair growth and circulation vary regionally between species and between dog and cat breeds to some degree.1,2 The skin consists of two main layers, the epidermis and the dermis.3-5 The general composition of the outer layer, the epidermis, is of avascular keratinized stratified squamous epithelium. The thicker vascular dermis lies underneath the epidermis and consists of tough fibroelastic tissue with a supportive and nourishing function. The dermis rests on a layer of loose connective tissue, known as the subcutis or hypodermis, which is composed of adipose tissue, the cutaneous trunci muscle (where present) and direct cutaneous arteries and veins. This layer is particularly abundant in most dogs and cats, but the quantity and elasticity of the skin will vary depending on the breed and on the physical condition of the animal.1,3 Variations in structure are present at different sites of the body surface. For example, the nose and footpads have a thick protective keratin layer, while the skin between the hindlimbs is fairly thin and sparsely haired. In addition, in most skin areas there are specialized epithelial appendages, such as hair follicles and sebaceous glands.6 The eyelids are dorsal and ventral folds of thin skin that are contin - uous with the facial skin, and their free edges meet to form the lateral and medial canthi.7 Histologically, the lids may be divided into four portions: the outermost layer of typical skin, the orbicularis oculi muscle layer, a stromal layer that contains a tarsal plate near the eyelid edge, and the innermost layer of palpebral conjunctiva.7
