When tissue cells are damaged, the defect is repaired and restored by parenchymal cell regeneration and/or fibrous connective tissue proliferation, which is called repair.

If the damaged parenchyma cells have regenerative ability and suitable conditions, they can be repaired and restored by the regeneration of adjacent parenchyma cells, because this repair can completely restore the structure and function of the original cells and tissues, so it is called regenerative repair or complete repair; Under pathological conditions, if parenchymal cells can't regenerate or only part of them can regenerate, the tissue defect will be completely or partially repaired by the new fibrous connective tissue (granulation tissue) rich in small blood vessels, forming a scar, which is called scar repair or incomplete repair because it can only restore the integrity of the tissue, but can't completely restore the original structure and function.

Regeneration refers to the proliferation of homologous cells to repair defects Description: ① Regeneration is a kind of cell proliferation; The essence of this proliferation is to repair defects, not to absorb necrotic substances or eliminate inflammatory factors (such as locally proliferating macrophages); ③ Regenerated cells should be exactly the same as the defective parenchymal cells, and regeneration can be divided into physiological regeneration and pathological regeneration.