The epidermis is the surface layer of the skin which consists of keratinized stratified squamous epithelium.

skin (superficial layers)

 

The dermis is the dense connective tissue layer beneath the epidermis. It contains blood vessels, nerves, lymph vessels, hair follicles and skin glands.

skin (low power) surface on the right

The glands of the skin consist mainly of the sebaceous (oil) glands and the sweat (sudoriferous) glands. Other specialized glands such as the mammary and anal glands are also skin glands.

Hairs cover almost the entire body surface of most animals. They are composed of keratinized cells and are constantly shed and replaced.

The shaft of a hair is visible above the skin surface; the root is below the skin surface: and the follicle is the gland-like structure which surrounds the root and forms the hair. Some hairs have a small muscle, the arector pili muscle, attached at the base of their roots. When the muscle contracts, the hair is pulled up into a more erect position resulting in what is commonly called "raised hackles." Specialized hairs, such as whiskers, have the same basic structure as normal hairs, but often have extensive sensory nerve receptors at their bases.