Healing and repair
During the healing process, damaged cells capable of proliferation regenerate. Different types of cells vary in their ability to regenerate. Some cells, such as epithelial cells, regenerate easily, whereas others, such as liver cells, do not normally proliferate but can be stimulated to do so after damage has occurred. Still other types of cells are incapable of regeneration. For regeneration to be successful, it is also necessary that the structure of the tissue be simple enough to reconstruct. For example, uncomplicated structures such as the flat surface of the skin are easy to rebuild, but the complex architecture of a gland is not. In some cases, the failure to replicate the original framework of an organ can lead to disease. This is the case in cirrhosis of the liver, in which regeneration of damaged tissue results in the construction of abnormal structures that can lead to hemorrhaging and death.

Repair, which occurs when tissue damage is substantial or the normal tissue architecture cannot be regenerated successfully, results in the formation of a fibrous scar. Through the repair process, endothelial cells give rise to new blood vessels, and cells called fibroblasts grow to form a