Hoof - Anatomy & Physiology
The keratin in the epidermis, when thickened and cornified, is referred to as horn. Horn is particularly resistant to mechanical and chemical damage. The outer surface of the hoof is composed of horn.
Structure
The epidermis of the horny hoof is termed the coronary epidermis. Its surface has a plantar aspect and newly formed hoof grows distally towards the plantar surface of the structure. Hoof wall is generally 5 - 10 mm in thickness and consists of 3 layers:
- A thin outer layer of shiny, dense horn, which effectively seals the hoof against dehydration and penetration.
- A thicker, intermediate layer of amorphorous horn, interspersed with tubular horn which provides reinforcement. This layer makes up the bulk of the hoof.
- An inner, lamellar layer, where epidermis and dermis interdigitate, anchoring the dead portion of the hoof to the living surface of the third phalanx.
The pigmentation in the outer layer of hooves is derived from melanocytes in the coronary epidermis. Deeper layers contain little melanin and therefore appear lightly coloured or white. The unpigmented layer of keratin forms a white line on the sole of the hoof, which delineates the sole from the wall when the plantar aspect is viewed.