Healing/Repair Flashcards
Regeneration
Replacement of damaged cells by replicating cells of the same type
Connective tissue framework remains intact (serves as scaffolding)
Scar formation
Replacement by connective tissue
Extracellular matrix
Interstitial matrix and basement matrix
Fibrous structural proteins: collagens, elastins
Water hydrated gels: proteoglycans, hyaluronan
Adhesive glycoproteins
Labile tissues
Continuously dividing
Ex: Hematopoietic cells of bone marrow
Squamous epithelium of skin, oral cavity
Columnar epithelium of GI tract
Stable tissues
No level of replication (G0 cell cycle)
Rapidly divide when stimulated
Ex: liver, kidney, pancreas, smooth muscle cells, fibroblasts
Epidermal Growth Factor (EGF)
Sources: activated macrophages, keratinocytes
Functions: mitogenic for keratinocytes, fibroblasts; stimulates keratinocyte migration
Transforming Growth Factor alpha (TGF-a)
Sources: activated macrophages, keratinocytes
Functions: stimulates proliferation of hepatocytes, other epithelial cells
Vascular Endothelial Growth Factor (VEGF)
Sources: mesenchymal cells
Functions: stimulates proliferation of endothelial cells; increases vascular permeability
Platelet-Derived Growth Factor (PDGF)
Sources: platelets, macrophages, endothelial cells, smooth muscle cells, keratinocytes
Functions: chemotactic; activated and stimulates proliferation of fibroblasts, endothelial cells; stimulates ECM protein synthesis
Fibroblast Growth Factors (FGFs)
Sources: macrophages, mast cells, endothelial cells
Functions; chemotactic, mitogenic for fibroblasts; stimulates angiogensis, ECM protein synthesis
Transforming Growth Factor beta (TGF-b)
Sources: platelets, macrophages, endotehlial cells, fibroblasts
Functions: chemotactic for leukocytes, fibroblasts; stimulates ECM synthesis; suppresses acute inflammation
Granulation tissue
Specialized tissue that fills in defect in organs when non-regenerative cells and/or connective tissue framework is destroyed
Organization
Process of transforming granulation tissue into a dense scar (blood vessels are less prominent, type III collage is replaced by type I)
Healing by First Intention
Clean, uninfected surgical incision approximated by surgical sutures
Epithelial regeneration principle mechanism of repair
Minimal contraction of wound
Healing by Second Intention
Large skin wound, extensive destruction, contamination, infection
Larger clot, more intense inflammation
Wound granulates in without closing gap with sutures
Wound contraction by microfibroblasts
Fibrosis
Excessive deposition of collagen and other ECM components in a tissue
TGF-b can drive fibrosis
Vitamin C
Function: cofactor for hydroxylation reactions (cross-linking of lysine and proline in collagen sythesis)
Deficiency: scurvy, impaired wound healing, blood vessel fragility
Basis of deficiency: diets lacking fruits and vegetables
ZInc
Function: cofactor for metalloenzymes (collagenase)
Deficiency: poor wound healing, growth impairment
Basis of deficiency: inadequate intake, alcoholism, chronic diarrhea, and inflammatory disease
Copper
Function: cofactor for lysyl oxidase, cross-links lysine and hydroxylysine
Deficiency: abnormal collagen cross-linking, poor wound healing, muscle weakness, neurologic deficits
Basis of deficiency: usually due to total parenteral nutrition
