Epithelial and connective tissues have the greatest capacity to regenerate. In small wounds and injuries, the epithelial and connective tissues often heal with normal tissue. The ability of muscle tissue to regenerate is very limited. Fibrous connective tissue often replaces damaged muscle tissue. As a consequence, the organ involved loses all or part of its ability to function. Nerve tissue has even less capacity to regenerate. Although neurons outside the brain and spinal cord sometimes regenerate at a very slow pace, most brain and spinal cord injuries result in permanent damage.