Tissue Repir.doc

Tissue Repair Definition Repair is a process patching the damaged tissue by regeneration of living cells around it. Repair of tissue involves two distinct processes, regeneration（再生） and fibroplasia or fibrosis（纤维性修复）. Regeneration : Division and proliferation of living cell around the damage tissue, the replacement of injured cells by cells of the same type Fibroplasia or fibrosis： Replacement by connective tissue, leaves a permanent scar. Types of regeneration Physiologic regeneration: is a normal process. blood, epithelial, bone and connective tissue cells show this phenomenon. Pathologic regeneration: In pathologic conditions. The proliferative potential of different cell types Labile cells（不稳定细胞）: can continue to proliferate throughout life. surface epithelia, bone marrow Stable cells（稳定细胞）: normally have a low level of replication but can undergo rapid division in response to stimuli. Liver cell, fibroblast, kidney, pancreas Permanent cells（永久性细胞）: have no regenerative capacity and can not undergo mitotic division in postnatal life. nerve cells, cardiac muscle cells. Regenerative processes by different tissues Regeneration of epithelial tissues Skin regeneration (Fig) Gland epithelium (Fig) Regeneration of connective tissues (Fig) Regeneration of blood vessels (angiogenesis) Vesculogenesis (血管形成) Angiogenesis (血管新生) (Fig) Regeneration of muscle Regeneration of neural tissues Control of cell growth Cell proliferation can be stimulated by injury, cell death. Cell replication is controlled largely by chemical factors in the microenvironment,which either stimulate or inhibit cell proliferation. Growth factors Growth factors are chemicals that are associated with cell growth There are three types stimulate the growth of different types of cell stimulate the growth of immune system (cytokines) stimulate the growth of blood cells (colony stimulating factors. Growth factors Epidermal growth factor (EGF) Transforming growth factor (TGF) Platelet-derive