Muscle: Muscle regeneration
Skeletal muscle contains numerous 'satellite cells' underneath the basal lamina, as shown in the photograph opposite. These are mononucleated quiescent cells. When the muscle is damaged, these cells are stimulated to divide. After dividing, the cells fuse with existing muscle fibres, to regenerate and repair the damaged fibres.
The skeletal muscle fibres themselves, cannot divide. However, muscle fibres can lay down new protein and enlarge (hypertrophy).
Cardiac muscle can also hypertrophy. However, there are no equivalent to cells to the satellite cells found in skeletal muscle. Thus when cardiac muscle cells die, they are not replaced.
Smooth cells have the greatest capacity to regenerate of all the muscle cell types. The smooth muscle cells themselves retain the ability to divide, and can increase in number this way.
As well as this, new cells can be produced by the division of cells called pericytes that lie along some small blood vessels.
Smooth muscle can also hypertrophy.