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Unformatted text preview: Regeneration and Repair Introduction: • Tissues are restored (to structural and functional integrity) via: • Removal of exudate; • Removal of cellular and tissue debris; • Replacement of cells and tissues lost *stable= only divide if killed/damaged Replacement of Cells and Tissues: • A) regeneration: if the cells (or tissue) replacing those lost in inflammation are identical or very similar (physiological or pathological) • B) repair: a broader term; it includes the process of replacement by cells and tissues, either of the same kind as those lost or of a different and often simpler type; pathological • Cells of the body are divided into 3 groups on the basis of their regeneration capacity: • Labile: continue to proliferate throughout life (epithelium—skin, bronchial epi, bone marrow epi, blood cells, endometrial cells); follow cell cycle from one mitosis to the next; these tissues can readily regenerate after injury as long as the pool of stem cells is preserved; contain stem cells that differentiate and replenish lost cells and maintain tissue homeostasis • Stable: low normal level of replication but able to divide in response to stimuli (parenchymal cells of glandular organs , mesenchymal cells, endothelial cells, fibroblasts and smooth muscle cells etc); considered to be on G0 but recruited to G1; minimal replicative activity in their normal state; ex renal tubular cells, liver cells • Permanent: cannot divide in postnatal life (neurons of CNS and cardiac muscle cells); have left the cell cycle; considered to be terminally differentiated and nonproliferative in post natal life; cannot be replaced themselves • **most common= regeneration and repair combo; identical cells and granulation tissue Regeneration • Much better developed in lower animals, and in protozoa and metazoan represent the major feature of reaction to injury • Physiological regeneration (replacement) in man: • Epidermis, blood, uterine mucosa, glandular epithelium • Great variation in the ability of different kinds of cells and tissues to regenerate : • →Supporting tissue regenerates best (fibrous, osseous, cartilage, blood vessels, epithelium, epidermis, renal tubular, glandular, intestinal, uterine) • →Other cells lose their ability to regenerate in postnatal life (cardiac muscle, nerve); require replacement by simpler tissue • Atypical regeneration of an organ- don’t arrange properly but are capable of dividing • In an organ, restoration depends not only upon the parenchymatous tissue’s ability to regenerate, but also whether or not the framework was destroyed ( eg in the skin: no sweat + sebaceous glands or hair; in liver: when architectural skeleton destroyed: regeneration is irregular producing an afunctional tissue: cirrhosis ); occurs when support frame is destroyed; lots of cells but no communication; function is impaired; ex hepatisis: kills liver cells by destroying framework; hepatocytes are stable and therefore replace themselves but don’t arrange properly, therefore not a functional liver...
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- Spring '11
- Pathology, cells, Collagen, Mesenchymal cells