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Equine - Anatomy & Physiology (view source)
Revision as of 11:30, 17 October 2012
, 11:30, 17 October 2012→Distal Sesamoid (Navicular) Bone
Dorsally, the articular surface is covered by hyaline cartilage. It articulates with the palmar aspect of the middle phalanx. The palmar flexor surface is characterised by a prominent '''sagittal ridge''' and is covered by fibrocartilage; providing a smooth surface for the deep digital flexor tendon to glide during weightbearing. The distal border contains a small articular facet of hyaline cartilage for articulation with the distal phalanx. The distal border contains numerous, synovium-lined, nutrient foraminae.
Dorsally, the articular surface is covered by hyaline cartilage. It articulates with the palmar aspect of the middle phalanx. The palmar flexor surface is characterised by a prominent '''sagittal ridge''' and is covered by fibrocartilage; providing a smooth surface for the deep digital flexor tendon to glide during weightbearing. The distal border contains a small articular facet of hyaline cartilage for articulation with the distal phalanx. The distal border contains numerous, synovium-lined, nutrient foraminae.
===Ligamentous Support===
Three ligaments support the navicular bone:
Three ligaments support the navicular bone:
*Paired '''collateral sesamoidean ligaments''': Originate from depressions on either side of the distal aspect of the proximal phalanx. They extend in a palmar direction to insert on the extremities and proximal border of the navicular bone; thereby acting to suspend the navicular bone.
*Paired '''collateral sesamoidean ligaments''': Originate from depressions on either side of the distal aspect of the proximal phalanx. They extend in a palmar direction to insert on the extremities and proximal border of the navicular bone; thereby acting to suspend the navicular bone.
*The '''distal sesamoidean (impar) ligament''' originates from the distal margin of the navicular bone and deep digital flexor tendon. It extends from the navicular bone proximally for 1.0-1.5cm and distally to the insertion of the deep digital flexor tendon on the distal phalanx (pedal bone).
*The '''distal sesamoidean (impar) ligament''' originates from the distal margin of the navicular bone and deep digital flexor tendon. It extends from the navicular bone proximally for 1.0-1.5cm and distally to the insertion of the deep digital flexor tendon on the distal phalanx (pedal bone).
The navicular is separated from the deep digital flexor tendon by the '''navicular bursa'''. There is no communication between the navicular bursa and the distal interphalangeal (coffin) joint.
The navicular bone is separated from the deep digital flexor tendon by the '''navicular bursa'''. There is no communication between the navicular bursa and the distal interphalangeal (coffin) joint.
===Innervation===
Sensory innervation to the navicular bone is supplied by the '''digital nerves'''. Nerves run distally through the collateral sesamoidean ligaments and within the distal sesamoidean (impar) ligament. Sensory innervation to the navicular bursa is also via digital nerves.
===Vasculature===
Arterial supply to the navicular bone is via anastomoses between '''medial and lateral palmar digital arteries'''. Proximally, a '''transverse plexus''' joins these arteries and gives rise to several small arteries that enter the formania of the navicular bone along its proximal border. Distally, branches connecting the medial and lateral palmar digital arteries form a '''distal navicular plexus'''; which give off additional small arteries that enter foramina along the distal border. These digital arteries supply most of the blood to the navicular bone. Anastamoses between the proximal and distal blood supplies occurs in the adult horse.
Venous drainage occurs via '''medial and lateral palmar digital veins'''.