Lecture 7 - healing Flashcards
Describe permanent cell proliferation
Terminally differentiated and can’t divide
No capacity for division (stuck in G0)
Neurons, myocardium
Describe stable cell proliferation
quiescent (resting) but can divide if required
Rapidly divide in response to stimuli (parenchyma of solid tissue)
Include endothelium, fibroblasts, smooth muscle
Liver - exceptional regeneration capacity - proliferation of remaining hepatocytes and progenitor cells (up to 90%)
Describe labile cell proliferation
Continuously dividing (and dying)
Surface epithelial cells - hematopoietic cells in bone marrow
Describe tissue repair
Regeneration - proliferation of cells that survive injury and retain capacity of proliferate
Connective tissue deposition - ECM/collagen deposition by fibroblasts
Fibrosis - thickening or scarring
Describe skin healing
Repair - restoration of tissue architecture and function
Primary union - only epithelial layer (regeneration) - proliferation of remaining cells and differentiation of skin stem cells
Secondary union - more expensive loss of cells or tissue - regeneration and scarring
What are the 3 stages of wound healing
Inflammation
Proliferation
Maturation
Describe inflammation stage of wound healing
Primary - coagulation (fibrin clot), inflammation (neutrophil infiltration and release of enzymes to clear debris), basal cell proliferation
Secondary - coagulation (larger fibrin clot), inflammation (more neutrophils and enzymes)
Describe primary proliferation stage of wound healing
Day 3 - granulation, angiogenesis, re-epithelization
Day 5 - new vessel formation, granulation (additional fibroblasts infiltrate, proliferate, deposition continues), basal cells recover
Describe secondary proliferation stage of wound healing
Day 3 - more granulation tissue formed
Day 5 - more granulation formed -> scar tissue
Describe primary maturation stage of wound healing
Week 2 - granulation (continued proliferation and deposition), inflammation (edema, leukocyte infiltration diminished), vessel formation diminished
Week 4 - granulation (complete - scar, dermal appendages destroyed - loss of tensile strength), inflammation resolved
Describe secondary maturation stage of wound healing
Week 4 - complete avascular scar with spindle shaped fibroblasts, dense collagen - fibroblasts -> myofibroblasts - cause construction (80% as strong as normal tissue)
What factors influence inflammation and repair
nutrition
metabolic status
Steroids
Infection
Mechanical factors
Blood supply
Describe chronic inflammation in unresolved wounds
Infiltration by mononuclear cells (macrophages and lymphocytes)
Tissue destruction induced by offending agent or inflammatory cells
Connective tissue deposition - angiogenesis and fibrosis occurs
Describe ulceration in unresolved wounds
Inadequate vascularisation
- decreased regeneration
- Increased connective tissue deposition
- Cavity formation
Describe excessive granulation tissue formation
Excessive amounts of granulation tissue, protrudes and block re-epithelialization
Describe excessive collagen production
keloids - scar tissue grows beyond boundaries ad doesn’t regress
Hypertrophic scars - deep layer damage to dermis
Describe contracture in unresolved wounds
Excessive contraction - comprise joint movement
Describe haematoma in bone fracture healing
Infiltration of neutrophils, later macrophages
Gradually phagocytosed and granulation tissue forms
Describe soft callus formation in bone fracture healing
progenitor cells from periosteum and bone marrow differentiate to produce bony matrix and some cartilage
Describe hard callus formation in bone fracture healing
After 2 weeks - ossification occurs
Describe remodelling stage of bone fracture healing
Excess callus resorbed by osteoclasts
Weight bearing bone framework re-established
What could go wrong in bone healing
Non-unison - Bones are too far apart
Fibrous union - granulation matures into fibrous tissue - instability or separation - poor blood supply or infection - Surgery usually required (correction of alignment, removing fibrous tissue, bone grafting, reproducing haematoma to restart healing process)