Relationship between normal appearance of fibrelike structure and degenerative changes in equine deep digital flexor tendon

Tendon in horse is the most important type of connective tissue which connects muscle to bone, constituting a vital component of the musculoskeletal system, by enabling movement. Tendons suffer from a wide range of disorders, which includes different types of mechanical injuries and degenerative diseases. The sample population was a deep digital flexure tendon (DDFT) at mid-meta carpal region of thirty adult horses examined using scanning electron microscopy (SEM). Sex distribution was not taken into account. Changes in its structural organisation due to aging following tendon degeneration was unknown. The complex structures of tendon and its distinctive characteristics have been well demonstrated by SEM techniques. The tendon structure under SEM showed a dense, regular connective tissue arrangement that reflects the mechanical requirement of this tissue. It is defined by thick regular bundles of longitudinal collagen fibres arranged in a zig-zag conformation. All tendons examined from these horses had no history of deep digital flexure tendinitis and were all macroscopically normal. The tendon showed a hierarchical structure, with collagen molecules forming fibrils (50 nm to 500 nm), which in turn comprise a fascicle (50 ?m to 300 ?m), and fascicles were aligned along the longitudinal axis of the tendon