bioRxiv preprint doi: https://doi.org/10.1101/396309; this version posted August 20, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Comparative Multi-scale Hierarchical Structure of the Tail, Plantaris, and Achilles Tendons in 2 the Rat 3 Andrea H. Lee, Dawn M. Elliott* 4 Department of Biomedical Engineering, University of Delaware 5 *Corresponding author. Tel.: +1 302 831 1295. E-mail address:
[email protected] (D.M. Elliott). 6 7 Keyword: Tendon, Hierarchical Structure, Multi-scale, Imaging 8 9 10 Abstract (500 words) 11 Rodent tendons are widely used to study human pathology, such as tendinopathy and 12 repair, and to address fundamental physiological questions about development, growth, and 13 remodeling. However, how the gross morphology and the multi-scale hierarchical structure of 14 rat tendons, such as the tail, plantaris, and Achillles tendons, compare to that of human 15 tendons are unknown. In addition, there remains disagreement about terminology and 16 definitions. Specifically, the definition of fascicle and fiber are often dependent on the diameter 17 size and not their characteristic features, which impairs the ability to compare across species 18 where the size of the fiber and fascicle might change with animal size and tendon function. 19 Thus, the objective of the study was to select a single species that is widely used for tendon 20 research (rat) and tendons with varying mechanical functions (tail, plantaris, Achilles) to 21 evaluate the hierarchical structure at multiple length scales.