Model Of Wound Healing Flashcards
Acute wound
Wound that heals in timely fashion
Chronic wound
Wound that have failed to proceed through an orderly and timely process to produce an anatomical and function integrity
- Medicare says presence longer than 30 days
Healing rate affected by…
Depth, location, cause of wound, patient age, physical condition
Acute inflammatory phase
Innate immunity lasting 24-48 hours
Subacute inflammatory phase
Involves both innate and acquired immunization lasting from 2-10 days
Proliferation phase
Lasting 2-20 days
Remodeling phase
Lasting from 9-up to 2 years
Inflammatory phase (acute and subacute) involves
- Vascular response to injury
- Cellular response to injury
- Chemical mediators of inflammation (histamine, leukotrienes, prostaglandins, bradykinin)
Vasoconstriction during inflammatory phase of wound healing
- Curtail blood flow via platelets
- Reduce oxygen delivery to wound -> producing hypoxia signaling to control wound healing via recruiting endothelial cells and facilitates angiogenesis in repair phase
- Wound space becomes hyperlactic & acidotic
Too much O2 during this phase impedes healing
Local hypoxia causes shift to…
Anaerobic glycolysis -> increase in lactate production -> activating angiogenesis and collagen synthesis
Platelets role in vasoconstriction
- First to arrive at injury site (activate, adhere, aggregate)
- Release serotonin -> vasoconstrictor
- Release PDGF (platelet derived growth factor) which is chemotaxic for neutrophils & macrophages
- Platelet derived fibrinogen converted to fibrin
- Seals injured area -> delays bacterial invasion
Vasodilation during inflammatory phase of wound healing
- Follows brief arteriolar vasoconstriction (once wound is closed from platelets)
- Histamine, prostaglandins, and leukotrienes released secondary to damaged tissue and mast cell degranulation
- Opens micro vascular beds -> increased heat, redness, cellular mediators & increased intravascular pressure
Cellular response during inflammatory phase of wound healing
- Polymorphonuclear leukocytes released from blood
- Neutrophils, eosinophils, basophils, mast cells
Neutrophil cellular response to inflammatory phase
- Proliferate in hypoxic acidotic environment
- Most phagocytic of granulocytes
- Produce superoxide to fight bacteria
- Secrete proteases and collagenases to hydrolysis necrotic tissue
- Wound pours forth pus (accumulation of dead cells that have phagocytized debris in wound)
- Short lifespan
Eosinophil cellular response to inflammatory phase
Modulate allergic inflammatory response, kill parasites
Basophil cellular response during inflammatory phase
Release histamine and heparin
Mast cell cellular respond during inflammatory phase
- Chemotactic factor (histamine) for leukocytes and macrophages
- Release histamine
- Release heparin -> stimulates migration of endothelial cells (for transition into proliferative phase) also accelerates activity of leukocyte phagocytosis
Macrophage cellular response during inflammatory phase
- Most important regulatory cell type
- Differentiate from monocytes when they leave the bloodstream
- Large phagocytotic cells that can ingest large microorganisms & debris
- Excrete ascorbic acid, hydrogen peroxide -> more recruitment (prolonging inflammatory phase)
- Tolerate severe hypoxia and acidotic environment
- Attracts fibroblasts, endothelial cells and vascular smooth muscle cells
- Essential for transition between inflammatory and repair phase
- Transcend all phases of wound healing (continue)
Leukocytes emigration sequence
- Margination & rolling (Sialyl-Lewis body & L-selectin)
- Adhesion (E-selectin)
- Transmigration (diapedesis - squeezing through cell membrane)
- Chemotaxis and activation
Lymphocyte cellular response to inflammatory phase
- Occurs slowly
- B & T lymphocytes
- Helper B cells
- Suppressor B cells
- Part of acquired immune response
- Complement system
Rubor
Indicative of increased blood flow
- Cardinal sign of inflammation, considered normal
Tumor
Fluid accumulation (plasma protein and blood cells)
- Cardinal sign of inflammation, considered normal
Calor
Increased blood flow to superficial tissues, histamine release
- Cardinal sign of inflammation, considered normal