Topic 4: Tissue Repair and Healing Flashcards
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
concurrent infection
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
Proliferation
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
- re-epithelialisation
Remodelling
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?
Age
-neonates: greater capacity for healing but lower energy stores
-elderly: decreased skin thickness and collagen content, loss of elasticity, slow healing
Malnutrition
Alcohol
-increase infection incidence
-diminished host resistence
-affects re-epithelialisation, collagen production, wound closure
Stress
-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)
- phagocytosis
- 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
