General patterns of microscopic structure of horse tendons

The work analyzed the results of the study of the tendons of the finger of a horse and presented general patterns of their structural organization. It was shown that the dense decorated connective tissue of the tendon, in the structure of which there are cells (tenoblasts and tenocytes) and intercellular matter with a predominance of bundles of collagen fibers, has a bundle structure, is in close connection with the loose connective tissue that forms endo- and peritenone. In turn, together these tissues form functional units in the tendon structure, which form the internal structure of the tendon as an organ. At the level of functional units, tendon tissue is remodeled. According to our data, the most labile link that allows the tendon to realize structural and metabolic adaptation to biomechanical load may be bundles of second-order collagen fibers, which differ in the variability of morphological (cross-sectional shape) and morphometric (cross-sectional area) indicators. Tendon tissue adapts to different mechanical loads by changing the structure that can be quantified. Thus, it varies the cross-sectional area of the collagen fiber bundles of orders II and III, the width of the endotenonium interlayers, the number of ovular capillary network within the functional unit, the number of tendon fibers "waves" per unit length. All this allows us to consider the tissue of the tendon, not inert, but a labile biological system that can adapt to functional load due to changes in morphological indicators.