(Top) Stretches of fiber families (λ) as a function of percent transmural depth at maximum deformation for SSRL and PSCR loading paths: fiber stretch λf (red); sheet stretch λs (green); normal stretch λn (blue); and λiλj (black). (Bottom) Change in initial angle (Δθij) between fiber families. Shearing of the sheet and normal directions dominates the response in SSRL, seen in the large value of Δθsn, whereas shearing of the fiber and normal directions dominates in PSCR, seen in the large value of Δθfn, which is distinguished in the extended model (11). i, j = f, s, n.