Changes

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.

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 solar surface is viewed.

[[image: Plantar hoof aspect.jpg|thumb|175px|left|A view of the plantar aspect of an equine hoof.  The wall has been removed on the right to show the underlying dermis.  ©Rachael Wallace2008]]

[[image: Plantar hoof aspect.jpg|thumb|175px|left|A view of the solar surface of an equine hoof.  The wall has been removed on the right to show the underlying dermis.  ©Rachael Wallace2008]]

The keratin in the sole is formed by the epidermis of the plantar aspect of the third phalanx and reaches a maximum thickness of 1 cm.  It is less resistant to abrasion than that of the outer layer of the hoof.  The central '''frog''' of the sole of a horse is located between the sharply inflected '''bars''' of the wall and is softer and less rigid than the keratin of the wall of the hoof.  Its elasticity is particulary important in the horse as pressure on the frog changes the angle of the walls when the horse stands on that foot.  The change in angle, termed the '''hoof mechanism''' increases the blood circulation in the hoof, increasing the supply of nutrients to the coronary epidermis.  This is closely correlated to hoof wall quality.

The keratin in the sole is formed by the epidermis of the plantar aspect of the third phalanx and reaches a maximum thickness of 1 cm.  It is less resistant to abrasion than that of the outer layer of the hoof.  The central '''frog''' of the sole of a horse is located between the sharply inflected '''bars''' of the wall and is softer and less rigid than the keratin of the wall of the hoof.  Its elasticity is particulary important in the horse as pressure on the frog changes the angle of the walls when the horse stands on that foot.  The change in angle, termed the '''hoof mechanism''' increases the blood circulation in the hoof, increasing the supply of nutrients to the coronary epidermis.  This is closely correlated to hoof wall quality.