Distal sesamoid bone
Os sesamoideum distale
- Synonym: Navicular bone; Os naviculaire
Definition
The horse has a distal sesamoid bone called the navicular bone, located within the hoof, that lies on the palmar aspect of the coffin joint between the second phalanx and third phalanx (coffin bone).
It is boat-shaped with a straight proximal border and a convex distal border that is attached to the distal phalanx by a strong ligament.
The flexor (palmar) surface is for the navicular bursa and the deep digital flexor tendon.
The articular surface is divided in two parts, a dorsal surface that articulates with middle phalanx and a small distal surface, that articulates with the articular surface of sesamoid of the distal phalanx.
The navicular bone in the horse is supported by the distal sesamoidean impar ligament and two collateral sesamoidean ligaments. The navicular bursa is located between the flexor surface of the navicular bone and the deep digital flexor tendon, which runs between the bursa and the distal phalanx.The central tarsal bone in the hock of the horse is homologous and analogous to the navicular bone of the human foot, and thus the navicular bone in the horse is a different structure from the eponymously labeled bone in humans.
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