Flashcards in Topic 4: Tissue Repair and Healing Deck (19):
When does inflammation resolve?
-no more loss of structural cells
-phagocytosis clean up
What is primary intention healing?
-lacerations with neat, clean edges or fractures where bony elements are precisely approximated
-ideal situation for wound healing
-no gap between sides of wound or tissue loss
What is secondary intention healing?
-large open wounds with tissue loss
-large inflammatory response
-haematoma and large fibrin meshword
-scarring and scabs
What are the four phases of tissue repair?
haematoma --> proliferation --> repair (anabolic and catabolic) --> remodelling
What is a haematoma?
-body of blood outside a vessel
-plasma and fibrin meshwork
-scaffolding by fibin
-stems bleeding (tamponade)
When can a haematoma become unhelpful?
large size, excessive duration, inside muscle compartment or brain
What is the process for the formation of a haematoma?
damaged vessel --> platelets + RBC --> clotting cascade --> platelet coagulation factors --> platelets activated by thrombin and aggregate --> platelets and fibrin scaffold
increase in number of immune cells and fibroblasts
Repair - catabolic
break down of dead, damaged, dying tissue by macrophages (phagocytic activity)
*occurs immediately except with bone repair
Repair - anabolic
-neoangiogenesis - formation of new blood vessels from pre-existing vessels, driven by cytokines
-fibroplasia and matrix deposition by fibroblasts
-collagen and ECM synthesis
final aggregation, orientation, arrangement of collagen fibres
-type III --> type I collagen
-contraction of wound from secondary to primary
What are some factors affecting tissue repair?
-neonates: greater capacity for healing but lower energy stores
-elderly: decreased skin thickness and collagen content, loss of elasticity, slow healing
-increase infection incidence
-diminished host resistence
-affects re-epithelialisation, collagen production, wound closure
-deregulation of immune system
-delayed wound healing
-physiological behavioural patterns: poor sleep, poor nutrition, decreased exercise, increased alcohol, increased cigarettes and drugs
How does muscle tissue heal?
-fibre degeneration (myonuclear death, impaired continuity of sarcolemma, myofibrils --> sarcomere units)
-rupture of vessels = haematoma
-damaged cells attract WBC (neutrophils, macrophages)
-satellite cells proliferate --> differentiate into myoblasts which fuse onto myotubules and release interleukins
-myotubes attempt to grow through scar tissue
How do ligaments heal?
-subcutaneous bleeding but quickly tamponaded
-macrophages act early
-proliferating fibroblasts close gap
-new tissue is fragile, viscous, stiff, weak
-stimulus directs matrix remodelling
Why is bone so strong?
-collagen fibres = tensile strength
-calcium salts = compressional stregnth
What are pre-requisites for bone healing?
adequate blood supply and mechanical stability
How does bone heal?
-no healing by scar tissue
-callus stage --> bridging between inflammatory and repair phase; bone is weaker at this stage
What is mechanobiology?
how physical forces and changes in mechanical properties of cells and tissues contributes to the development, cell differentiation, physiology and repar