1 Healing & Repair Dr. Srikumar Chakravarthi Repair & Healing: Are they same? Repair :Regeneration of injured cells by cells of same type, as with regeneration of skin/oral mucosa (requires basement membrane) Epidermis, GI, blood, liver. Healing :Replacement by fibrous tissue (fibroplasia, scar formation) Incision, MI, stomach ulcers. Tissue Regeneration Controlled by biochemical factors released in response to cell injury, cell death, or mechanical trauma – Most important control: inducing resting cells to enter cell cycle – Balance of stimulatory or inhibitory factors – Shorten cell cycle – Decrease rate of cell loss Varieties of Proliferative Potential Labile (always dividing) cells: – Replace dying cells – Epithelia: skin, oral cavity, exocrine ducts, GI tract, GYN, hematopoietic. Stable (quiescent) cells: – Usually G 0 and low rate of division – Driven into G 1 and rapid proliferation – Liver, kidney, pancreas, endothelium, fibroblasts Permanent (non-dividing ) cells: – Permanently removed from cell cycle – Irreversible injury leads only to scar – Nerve cells, myocardium, skeletal muscle Stem cells Remarkable potential to develop into many different cell types in the body. Repair system for the body, they can theoretically divide without limit to replenish other cells. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function (muscle cell, RBC, neuron). Embryonic, Adult ( BM, tissue)
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Healing & Repair
Dr. Srikumar Chakravarthi
Repair & Healing: Are they same?
� Repair :Regeneration of injured cells by cells of same type, as with regeneration
of skin/oral mucosa (requires basement membrane) Epidermis, GI, blood, liver.
Stem cells� Remarkable potential to develop into many
different cell types in the body.
� Repair system for the body, they can theoretically divide without limit to replenish other cells.
� When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function (muscle cell, RBC, neuron).
� Embryonic, Adult ( BM, tissue)
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Intercellular Signaling
� 3 pathways
– Autocrine: cells have receptors for their own secreted factors (liver regeneration)
– Paracrine: cells respond to secretion of nearby cells (healing wounds)
– Endocrine: cells respond to factors (hormones) produced by distant cells,
circulate in blood
Growth Factors and Molecular Events
� Polypeptide growth factors with many (pleiotropic) effects : Proliferation, migration, differentiation, remodeling (all part of wound