The epidermis is formed by layers of flat cells composing a stratified squamous epithelium. New cells originate in the lowest layer and become keratinized as they are pushed to the surface. Keratin is a fibrous protein that also forms the substance of hair, horns and hoofs. At the ultrastructural level it is deposited in a fibrillar form which then may be incorporated into a granular form.
Hair is formed by epithelial cells of a papilla at the base of the follicle.
There is considerable variation in the rate of hair growth in meat animals. For example, the average length of bovine hair may reach a maximum between 6 and 24 months, and then may decrease. The underlying sequence of events in hair growth is due to the periodic shedding of hairs from their follicles. The bulb at the base of the hair eventually becomes hard and clublike. This holds the hair in its follicle for some time, but no further growth is possible.