The hoof is made up by an outer part, the hoof capsule (composed of various cornified specialised structures) and an inner, living part, containing soft tissues and bone. The cornified material of the hoof capsule is different in structure and properties in different parts. Anteriorly, it covers, protects and supports P3 (also known as the coffin bone, pedal bone, PIII). Posteriorly, it covers and protects specialised soft tissues (tendons, legaments, fibro-fatty and/or fibrocartilaginous tissues and cartilage). The upper, almost circular limit of the hoof capsule is the coronet (coronary band), having an angle to the ground of roughly similar magnitude in each pair of feet (i.e. fronts and backs). These angles may differ slightly from one horse to the other but not markedly. The walls originate from the coronet band. Walls are longer in the anterior portion of the hoof (toe), intermediate in length in the lateral portion (quarter) and very short in posterior portion (heel). Heels are separated by an elastic, resilient structure named the 'frog'. In the posterior part of the foot, above the heels and the frog, there are two oval bulges named the 'bulbs'.
When you pick up the hoof and you look at its lower surface, you can see the wall's free margin, encircling most of the hoof. In the central area, you can see the triangular frog. Lateral to the frog, are two grooves, deeper in their posterior portion, named 'collateral grooves'. At the heels, the posterior portion of the walls bend inwards sharpy, following the external surface of collateral grooves; here they are named bars. The lower surface of the hoof, from the outer walls and the inner frog and bars, is covered by an exfoliating keratinised material, called the 'sole'.
Just below the coronet, the walls are covered for about an inch by a cornified, opaque material named the 'periople'. In the posterior part of the hoof, the periople is thicker and more rubbery over the heels and it merges with frog material. Not all horses have the same amount of periople. Dry feet tend to lack this substance, which can be substituted with hoof dressing.
