Digits Veterinary Anatomy

Ox Standard (Artiodactyl):
- 2 Functional Digits (III & IV).
- 2 Accessory Digits (Dewclaws).
- P3 is Cloven (coffin bone).
- 2 Proximal Sesamoids per digit (4 total).

DIGITS OF THE OX — THE CLOVEN HOOF

The ox is an Artiodactyl ('even-toed') — it walks on TWO functional digits (III and IV), with two non-weight-bearing dewclaws (II and V).

FUNCTIONAL DIGITS (III medial, IV lateral):
Each functional digit has 3 phalanges + 3 sesamoid bones.

P1 (Proximal Phalanx) — 'long pastern bone':
• Long bone with proximal articular surface (cup) for cannon trochlea.
• Distal end articulates with P2.
• Site of attachment for several flexor/suspensory ligaments.

P2 (Middle Phalanx) — 'short pastern bone':
• Short and wedge-shaped.
• Lies inside the hoof partly.

P3 (Distal Phalanx) — 'coffin bone' / 'os ungulare' / 'pedal bone':
• The cloven hoof bone — encased entirely within the hoof horn.
• Pyramidal in shape; has axial (medial) + abaxial (lateral) surfaces.
• Bears the solar surface below + the extensor process on top (cranial) for insertion of common digital extensor.
• Receives weight via P2 above and the corium (laminar attachment to hoof wall) around it.

SESAMOID BONES (per digit):
• 2 Proximal Sesamoids — at the back of the fetlock joint, embedded in the suspensory ligament; they articulate with the trochlea of cannon → form the FETLOCK joint together.
• 1 Distal Sesamoid (Navicular) — small boat-shaped bone behind P3, embedded in the deep digital flexor tendon. Lies inside the hoof.

DEWCLAWS (Digits II + V):
• Small, non-weight-bearing.
• Each contains a small phalanx skeleton (P1, P2, P3) — but in modern cattle these are reduced/incomplete.
• Located above and behind the fetlock.
• Cosmetically removed in some breeds.

HOOF CAPSULE:
The horn capsule that covers P3 + part of P2. Composed of:
• Wall (paries) — visible from outside; grows down from coronet.
• Sole (solea) — bottom; grows from solar corium.
• Bulb (heel) — soft caudal area.
• White line (zona alba) — junction of wall + sole; weakest area, common laminitis site.
• Each functional digit has its own complete horn capsule → 'cloven hoof' = 2 horn capsules per foot.

HORSE DIGIT (single, digit III only):
• Same 3 phalanges + 2 proximal sesamoids + 1 distal (navicular) sesamoid.
• P3 is the 'coffin bone' inside the single hoof; bears wings, retrossal processes, palmar processes.
• Hoof capsule encloses everything.

DOG DIGIT (digits II-V functional, I = dewclaw):
• Each digit has 3 phalanges + sesamoids.
• P3 is 'ungual crest' = claw-shaped — encased in the keratinous claw.
• Digital pads (toe + metacarpal pads) bear weight (NOT the bone surfaces directly).

UG MEMORY: 'Ox = 2 functional + 2 dewclaws, P3 cloven; Horse = 1 functional, P3 coffin + navicular; Dog = 4 functional + dewclaw, P3 ungual claw.'