Claws, Dewclaws, and Hoof

Claws

•  are hard outer coverings of distal digits.

• They are non-retractable except in most cats and help with traction, defense, and catching prey.

Dewclaws

• are evolutionary remnants of digits.

• In dogs they are the first digit, and in cows, pigs, and sheep they are the second and fifth digits.

Hoof

• The hoof, or ungula, is the horny outer covering of digits.

• Each hoof covers a digit, and not all hooves are weight-bearing.

Hooves rest on the corium, where the inner layer is modified dermis rich in blood supply and the outer hoof layer is modified epithelium with no sensation.

Corium

• The corium is the sensitive tissue supporting both claws and hooves.

• It is well innervated and sensitive to pain.

• In the equine foot, there are 5 types: laminar, perioplic, coronary, sole, and frog corium.

Equine skeletal foot

•  the distal part of the second phalanx,

•  the distal sesamoid bone (navicular bone), 

•  the third phalanx (coffin bone).

These are covered by corium, which is covered by the hoof.
The hoof and corium form interdigitations called laminae.

Laminitis

Laminitis is inflammation of the laminae caused by certain disease processes.
- The lamina swells, blood supply is inhibited, and in severe cases the attachment between the hoof wall and distal phalanx (coffin bone, P3) detaches.

Parts of the equine hoof

• Wall: convex outer portion divided into toe, quarters, and heel.

• Sole: plantar or palmar surface, (White line).

• Frog: triangular horny structure.

• Central sulcus: cleft.

• Digital cushion.

• Lateral cartilages.

Horns

• Horns are masses of horny keratin that grow continuously and are not sex related.

• They are structurally similar to hair and are epidermal in origin.

not sex specific, epidermal in origin, grow continuously, and may be hollow with direct communication to the frontal sinus.

Antlers:

primarily on males, dermal in origin, shed annually, are bony protuberances from the skull, and lack a central core and internal blood supply; they are covered by velvet skin during growth.