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. Author manuscript; available in PMC: 2017 Feb 1.
Published in final edited form as: Placenta. 2015 Dec 20;38:57–66. doi: 10.1016/j.placenta.2015.12.011

Figure 1.

Figure 1

FM collagen fiber recruitment: Traditional recruitment modeling assumes that a collagen fiber does not bear load until the collagen fiber is straightened, where K is the elastic constant. Gradual recruitment of collagen fibers results in a non-linear tension-stretch relationship. Initially all collagen fibers are crimped and do not bear load, which results in the toe region. With increased stretch, the fiber with the least amount of crimp, fiber 1 in this schematic, will bear load and become straightened. With increased stretch, fibers 2 and 3 will become straightened, causing the tension-stretch curve to increase in a non-linear manner. As stretch continues to increase, all collagen fibers (1, 2, 3, and 4) will bear load and become straightened resulting in a highly linear region on the tension-stretch curve. When a small population of fibers is present, the tension-stretch curve is discrete (indicated by the solid line), but when a large population of fibers exists, the tension-stretch curve is continuous (dashed line).