The primary cause of anisotropic diffusion in biological tissues is the heterogeneous structure of the tissue itself. Tissues are composed of various cell types, extracellular matrix components, and fibrous elements that create directional pathways favoring or impeding the diffusion of substances. Factors such as the orientation of fibers, the density of cellular components, and even the biochemical properties of the extracellular matrix can contribute to anisotropy in diffusion.
