Schematic representation of myofibril reorganization in a 2D myocyte.

(A) red: actin; blue: nucleus; green: FAs. The FAs can spread throughout the ECM island (outlined by solid black island). (B) Net force (F) exerted on bound integrins, as determined by the sum of all forces exerted by the anchoring premyofibril vectors, recruits free integrins and promotes growth of FAs. For the purposes of modeling the bound integrins connected to premyofibrils are labeled ρp(r). (C) Continued recruitment of free integrins to the growing FA at the cellular corners is associated with enhanced bundling of the premyofibrils and subsequently increased traction. (D) Built upon the premyofibrillar network, the nascent myofibrils align in parallel and develop into a fully organized bundle, further amplifying local force to result in FA maturation. For the purposes of modeling the bound integrins connected to nascent myofibrils are labeled as ρn(r). (E) Bound integrins with zero net force cannot recruit free integrin and are disassociated from the membrane, leading to release of the attached fiber (F). Consequently, contractile fibers on shorter axes (G) are less bundled than that following the longest diagonal of the cell. (H) Qualitative schematic of model implementation algorithm.

(A) 红色标记肌动蛋白（actin），蓝色标记细胞核（nucleus），绿色标记黏着斑（Focal Adhesions, FAs）。黏着斑可在黑色实线勾勒的细胞外基质（Extracellular Matrix, ECM）岛区域内铺展。
(B) 锚定前肌原纤维（premyofibril）矢量产生的总合力，即为作用于结合态整联蛋白（integrin）的净力(F)；该净力可募集游离整联蛋白，并促进黏着斑的生长。为便于建模，将与前肌原纤维相连的结合态整联蛋白标记为ρp(r)。
(C) 持续将游离整联蛋白募集至细胞角落处正在生长的黏着斑，会增强前肌原纤维的束化程度，进而提升细胞牵引力。
(D) 在前肌原纤维网络的基础上，新生肌原纤维（nascent myofibril）呈平行排列并发育为高度有序的束状结构，进一步放大局部作用力以推动黏着斑成熟。为便于建模，将与新生肌原纤维相连的结合态整联蛋白标记为ρn(r)。
(E) 净力为零的结合态整联蛋白无法募集游离整联蛋白，会从细胞膜上解离，进而引发其所附着纤维的释放（对应图F）。因此，沿较短轴分布的收缩纤维（对应图G），其束化程度不及沿细胞最长对角线排布的收缩纤维。
(H) 模型实现算法的定性示意图。