Healing and Repair 8-5-15 Flashcards
What is regeneration replacing damaged cells with, what is scar formation replacing damaged cells with?
regeneration: replicating cells of the same type
scar formation: connective tissue
What do you need to remain intact in order to have regeneration?
connective tissue framework-scaffolding for replacement of residual uninjured cells (cells must have capacity to divide)
What is labile tissue?
continuously dividing
lost cells replaced by
-maturation of stem cells
-proliferation of mature cells
Examples:
Hematopoietic cells of bone marrow
Squamous epithelium of skin, oral cavity, cervix, vagina
Columnar epithelium of GI tract
What is stable tissue?
low, no level of replication
-G0 cell cycle
rapidly divide when stimulated
-G1 cell cycle and beyond
Example
-Liver
kidney, pancreas, smooth muscle cells, fibroblasts
What are permanent tissues?
terminally differentiated, non proliferative in postnatal life
-brain and heart
What are is the pro and the con of scar formation?
Con-fibrous tissue loss of function-loss of parenchymal cells
Pro-structural stability for injured tissue to continue function
What are important mediators of angiogenesis?
VEGF
FGFs(fibroblast growth factor)
PDGF(platelet growth factor)
TGF-B
What induces VEGF?
hypoxia
What do fibroblasts do? What are they activated by?
synthesize connective tissue proteins
-growth factors (PDGF, FGF, TGF-B)
What is granulation tissue? What does it consist of?
specialized tissue that fills in defects in organs when non-regenerative cells and or connective tissue framework is destroyed
Consists of:
- proliferating Fibroblasts (laying down immature connective tissue (collagen type 3))
- proliferating new blood vessels
-only during attempt to heal destroyed tissue
What is organization? What happens with time?
process of transforming granulation tissue into a dense scar
With time: blood vessels become less prominent, collagen matures (type 3 collagen replace type 1)
What color is mature collagen stain on a trichrome stain?
blue
What are the7 steps to healing of skin wounds?
- inflammation
- blood clot (fibrin, fibronectin) forms
- Epithelium regenerates to cover
- cells proliferate and migrate to defect
a. macrophages-remove debris, secrete cytokines
b. fibroblasts-produce extracellular connective tissue matrix
c. myofibroblasts contract the wound - simultaneously capillaries at edge of defect proliferate and extend into the defect under the influence of chemical mediators
- over weeks to month defect filled with granulation tissue, becomes remodeled to mature collaged( scar)
- Wound acquires strength through the process
What is healing by first intention?
- clean uninfected surgical incision approximated by surgical sutures
- epithelial regeneration principle mechanism of repair
- small scar
- minimal contraction of wound
What is healing by second intention?
- large skin wound
- extensive destruction, contaminated infected
- larger clot, more intense inflammation
- wound granulates without closing gap with sutures
- process of healing same
- takes longer
- wound contraction by myofibroblasts
