RESPONSE OF MUSCLE TO INJURY

The response of muscle to injury depends on the muscle type. The wound closure mechanism always involves the proliferation of fibroblasts

A. Skeletal Muscle: Small, mononucleatcd satellite cells are scattered in adult skeletal muscles within the basal lamina of the mature fibers. While mature skeletal muscle fibers are incapable of mitosis, the normally quiescent satellite cells can divide following muscle injury, differentiate into myoblasts, and fuse to form new skeletal muscle fibers.

B. Cardiac Muscle: Cardiac muscle has little regenerative ability beyond early childhood. Lesions of the adult heart are repaired by replacement with connective tissue scars.

C. Smooth Muscle: Smooth muscle contains a population of relatively undifferentiated mono nucleated smooth muscle precursors that proliferate and differentiate into new smooth muscle fibers in response to injury. The same mechanism appears to be involved in adding new muscle to the myometrium as the uterus enlarges during pregnancy to accommodate the growing fetus.