11/30/2023 0 Comments Pathological hypertrophy examplesStem cells proliferate very slowly or lie dormant, but can rapidly proliferate when required Stem cells divide repeatedly to replenish losses Tissues can be classified into 3 types depending on the ability to self-repair, which depends on their stem cell activity: Tissue type Thus where stem cells are present, new cells can be formed in response to disease, environmental stressors or normal replenishment of cells at the end of their lifespan. They are key to determining a tissue’s ability to replenish lost cells, as they are able to self-renew indefinitely. Stem cells are immature cells that can go on to differentiate into various specialised, mature cell types within a certain lineage. Cell differentiation – cell takes on specialised form and function.Cell division – cell enters the cell cycle.Ultimately, cell signalling results in one of four outcomes: Examples of growth factors include epidermal growth factor, vascular endothelial growth factor and platelet-derived growth factor. Growth factors act on cell surface receptors, stimulating transcription of genes that regulate the cell cycle. If cell proliferation becomes uncontrolled, and cells no longer respond to inhibitory signals, cancer can develop. Signalling may be via hormones, local mediators such as growth factors or direct cell to cell contact. Physiological cell proliferation is primarily regulated by chemical signals which either promote or inhibit proliferation. Increased cell numbers are therefore seen with either increased cell proliferation or decreased cell death.Ĭell proliferation occurs both in both physiological and pathological conditions. The size of cell populations depends on the rate of 3 factors:
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