what are the 4 phases of tissue repair?
- hemostasis: clot formation
- inflammatory: infilatration of immune cells, initiation of repair
- reparative phase (proliferative): migration of cells, formation of granulation tissue
- wound contraction and scarring (not always)
what is the difference between regeneration and repair?
- regeneration - complete restoration of tissue architecture and function (good as new)
- repair - restoration of function but altered architectures (scars)
what is hemostasis?
transition of blood from liquid to a fibrillar gel
what are the primary and secondary goals of hemostasis?
- primary: stop the bleeding
- secondary: initiation of healing
in hemostasis, disruption of platelets leads to ___. the clot unites the edges of the wound, and the ___ provides a scaffold for future ___
- coagulation cascade
- cell migration and repair
how is a clot different in the oral cavity than other areas of the body?
it is softer and more easily detached
what is primary hemostasis?
- vascular spasm (constriction) and initial platelet plug in a damaged vessel
primary hemostasis is initiated by exposure of ___ in subendothelium (normally separate from the lumen) to circulating ___
- von willebrand factor
what is von willebrand factor?
causes platelet aggregation by interacting with platelet surface proteins (GP1b-IX-V receptor complex)
platelets can also bind collage directly by ___ and ___
- GPVI (glycoprotein VI)
- alpha-2-beta-1 integrin
in primary homeostasis, platelets activate and dump out tons of preformed cytoplasmic vesicles containing what?
- more von willebrand factor
- coagulation factors V and XIII
- platelet agonists serotonin and ADP
in primary hemostasis, ___ anchors platelets together
what is secondary hemostasis?
- blood coagulation
- occurs simultaneously with or just after primary hemostasis
- complex cascade of extrinsic and intrinsic pathways
what is the extrinsic pathway of secondary hemostasis?
- factor VII and tissue factor interactions (found around, often on fibroblasts) initiate the cascade
- called extrinsic because it requires tissue factor which is normally not found in blood
what is the intrinsic pathway of secondary hemostasis?
- initiated by damaged endothelium (collagen exposure)
- called intrinsic because it involves factors found in the blood (ie. not tissue factor)
the main point of secondary hemostasis is the conversion of ___ into ___ which in turn converts soluble ___ into insoluble ___.
many of these steps require ___
in secondary hemostasis, ___ cross-links and forms a mesh, trapping red and white cells, resulting in a ___
- blood clot
what is inflammation?
tissue injury and leakage of plasma proteins attracts macrophages and lymphocytes
what types of cells are involved in inflammation?
- inflammatory cells
- leukocyte involvement - particularly T cells
describe inflammatory cells involved in inflammation
resident cells, circulating cells from disrupted blood vessels, cells infiltrating from intact local blood vessels (diapedesis)
describe neutrophils involved in inflammation
- first on the scene, activated by antibody-antigen interactions, LPS, complement system
- bacterial destruction, also damages surrounding tissues
describe macrophages involved in inflammation
second to arrive (after neutrophils), clear damaged tissue remnants and foreign material
which phase involves the mobilization of adjacent cells (epithelium) and endothelial cell proliferation and angiogenesis?
*there are obviously steps in between*
what is the result of epithelial cell migration in the reparative/proliferative phase?
- formation of new basal lamina, redistribution of integrin receptors, and formation of new hemidesmosomes (cells lay their own track)
- eventually forms a thin cover over the wound
what is the result of fibroblast recruitment after endothelial cell migration in the reparative/proliferative phase?
- after fibroblasts are recruited, they proliferate in the wound
- both resident fibroblasts and new ones from mesenchymal progenitor cells
- collagen production begins to fill the defect, forming a scaffold
in the reparative/proliferative phase, which cause endothelial cell proliferation and angiogenesis?
TGF-beta, VEGF, and FGF-2
describe the process of wound contraction
- specialized fibroblasts - myofibroblasts, increased actin/myosin
- align around wound, form cell junctions and attach to CT fibril around wound
- draw wound edges together
- initial collagen deposition by fibroblasts: immobile scar tissue, can be remodeled
what is describe as bacterially induced inflammation at gingival margins, causing destruction of connective tissues?
in periodontal disease, how is pocket epithelium formed?
via apical migration of junctional epithelium
___ can arrest the spread of infection into periodontal tissues