Pathology - Cell Repair
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- What are the phases of the cell cycle?
- G1 (presythetic), S (DNA synthesis), G2 (premitotic), M (mitotic), G0 (resting phase)
- What are the 3 different types of regenerative capacities of cells?
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continuously dividing (labile) cells
quiescent (stable) cells
non-dividing (permanent) cells - What are some examples of labile cells?
- stratified sqaumous epithelia of skin, oral cavity, vagina, cervix; cuboidal epithelia of exocrine ducts; columnar epithelium of GI tract, uterus, fallopian tubes; transitional epithelium of urinary tract; hematopoietic cells
- What are some examples of quiescent cells?
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(can regenerate; driven from G0 to G1 after cell loss)
parenchymal cells of liver, kidney, pancreas, vascular endothelial cells, smooth muscle - What are some examples of non-dividing cells?
- nerve cells and cardiac myocytes
- What does epidermal growth factor (EGF) do?
- promotes growth of endothelial cells, fibroblasts, and epithelial cells; is a progression factor
- What other growth factor is homologous to EGF?
- TGF-alpha (transforming growth factor)
- What types of cells synthesize/secrete platelet-derived growth factor (PDGF)?
- activated platelets and macrophages, endothelial and smooth muscle cells, tumors
- What are the functions of PDGF?
- promotes chemotactic migration and proliferation of monocytes, fibroblasts, and smooth muscle cells
- Is PDGF a competence factor or a progression factor?
- competence factor: promotes proliferative response of fibroblasts and smooth muscle cells upon concurrent stimulation by progression factors
- What is the function of basic fibroblast growth factor (b-FGF)?
- promotes synthesis of extracellular matrix protein (including FIBRONECTIN) by fibroblasts, endothelial cells, monocytes, and other cells (eg can induce all steps necessary for angiogenesis)
- What is the function of fibronectin, and what factor stimulates its synthesis?
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-is chemotactic for fibroblasts, monocytes, endothelial cells
-promotes angiogenesis
-links extracellular matrix components and macromolecules to cell-surface integrins
-stimulated by b-FGF - What are the functions of transforming growth factor beta (TGF-beta)?
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-chemotactic for monocytes and fibroblasts
-is a growth inhibitor (at high conc) for many cell types
-may aid in repair process - What are the macrophage derived growth factors, and what are their functions?
- TNF and IL-1 (e.g. cytokines); promote chemotaxis and proliferation of fibroblasts
- What is granulation tissue?
- following acute inflammatory response, nonregenerated parenchymal cells are replaced by proliferating fibroblasts and vascular endothelium; pink, soft tissue beneath scab
- What is the progression from granulation tissue to scar tissue?
- granulation tissue accumulates collagen (connective tissue matrix) produced by fibroblasts; tissue becomes less cellular and less vascular
- What is an example of a wound healing by first intention?
- healing of a surgical incision closed with sutures
- What is a key characteristic of wound healing by second intention?
- wound contraction; w/in 6 weeks large skin defects shrink to 5-10% of original size; e.g. infarction, abscess, ulceration, large wounds
- What are some factors that delay or impede repair?
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infection, impaired circulation, retention of debris, dietary deficiency of ascorbic acid or protein (required for collagen formation)
*metabolic d/o's, e.g. diabetes (assoc w/poor circulation and susceptibility to infection)