Bones & Muscle

Bones are anisotropic but are approximately transversely isotropic. In other words, bones are stronger along one axis than across that axis, and are approximately the same strength no matter how they are rotated around that axis.
The stress-strain relations of bones can be modeled using Hooke's law, in which they are related by elastic moduli, e.g. Young's modulus, Poisson's ratio or the Lamé parameters. The constitutive matrix, a fourth order tensor, depends on the isotropy of the bone.
σij = Cijklεkl .

There are three main types of muscles:
Skeletal muscle (striated): Unlike cardiac muscle, skeletal muscle can develop a sustained condition known as tetiny through high frequency stimulation, resulting in overlapping twitches and a phenomenon known as wave summation. At a sufficiently high frequency, tetany occurs, and the contracticle force appears constant through time. This allows skeletal muscle to develop a wide variety of forces. This muscle type can be voluntary controlled. Hill's Model is the most popular model used to study muscle.
Cardiac muscle (striated): Cardiomyocytes are a highly specialized cell type. These involuntarily contracted cells are located in the heart wall and operate in concert to develop synchronized beats. This is attributable to a refractory period between twitches.
Smooth muscle (smooth - lacking striations): The stomach, vasculature, and most of the digestive tract are largely composed of smooth muscle. This muscle type is involuntary and is controlled by the enteric nervous system.