Mechanical adaptation on the microstructural components of biological tissues

肌腱和韧带具有胶原纤维束（直径约100μm）、纤维（直径约1μm）、原纤维（直径50- 500 nm）和分子等分级结构。纤维束由纤维和原纤维组成，包埋在蛋白多糖等基质中。被称为腱内体的薄鞘包围着这些束。其结构和力学性能的基本知识是必不可少的肌腱和韧带的生物mechanics.In这项研究中，从小鼠尾肌腱获得的束在盐水溶液中搅拌，并地面物质被删除的束。用扫描电镜（SEM）和原子力显微镜（AFM）观察了拉伸试样的微观结构。从纤维束分离的原纤维被拉伸至失效。研究了基质对纤维束力学性能的影响以及纤维束与纤维束之间的力学关系，结果表明：在盐水溶液中搅拌纤维束可以去除基质，降低纤维束的拉伸强度和切线模量。很明显，基质作为胶原纤维之间的类水泥物质，是决定纤维束拉伸性能的基本成分。原纤维的拉伸强度（86.3±8.2 MPa（平均值±S.E.））比束大3.3倍。因此，原纤维没有失败，但地面物质失败在故障的束。

Tendons and ligaments have such hierarchical structures as collagen fascicles (the diameter of about 100μm), fibers (the diameter of about 1μm), fibrils (the diameter of 50-500nm), and molecules. The fascicles consist of fibers and fibrils embedded in ground substances such as proteoglycans. Thin sheaths called endotenon surround the fascicles. The basic knowledge of their structure and mechanical properties is essential to the biomechanics of tendons and ligaments.In this study, the fascicles obtained from mouse tail tendons were stirred in a saline solution, and ground substances were removed from the fascicles. These specimens were stretched to failure and their microstructure was observed with a scanning electron microscope (SEM) and atomic force microscope (AFM). The fibrils separated from the fascicles were stretched to failure. We studied the effects of the ground substances on the mechanical properties of the fascicles and the mechanical relationships between the fibrils and fascicles.The stirring of fascicles in a saline solution removed ground substances from the fascicles and decreased their tensile strength and tangent modulus. It is clear that ground substances act as a cementlike substance between collagen fibrils and are a basic component to determine the tensile properties of fascicles. The tensile strength of fibrils (86.3±8.2 MPa (Mean±S.E.)) was 3.3 times larger than that of fascicles. Therefore, fibrils did not fail but ground substances failed at the failure of fascicles.