L9 Healing Flashcards
Describe tissue regeneration in the liver
Tissue regeneration liver-
enormous capacity to regenerate as long as it has the underlying structure
• Regeneration occurs following most injury
• Resection or cell death
(necrosis or apoptosis)
• Surgical removal (60%) restored in 4-6 weeks
• Quiescent hepatocytes become competent to enter the cell cycle in response to cytokines and growth factors.
• Replicate once or twice and then return to quiescence
• Eg. Liver regeneration after resection in zebra fish partial hepatectomy
• Injury that ablates structure and function (infection and inflammation) causes incomplete regeneration- scarring
Loss of the extra cellular matrix structure
What is a granulation tissue?
pink vascular tissue when scab is picked too soon
• Proliferating fibroblasts: cell that is bound in the extra cellular matrix, proliferate and produce the extra cellular matrix
• Loose ECM
• New capillaries
Sequential steps of Tissue repair by connective tissue
1) angiogenesis
2) Fibroblasts migration & proliferation
3) Deposition of ECM, scar
4) Remodeling -Maturation and reorganization of the fibrous tissue
M1
Classical macrophage activation (M1)
− Secrete cytokines that stimulate inflammation
− Ingest and eliminate microbes and dead tissue
M2
Alternative macrophage activation (M2)
− Initiate the process of tissue repair
− Secrete growth factors that promote angiogenesis, activate fibroblasts and stimulate collagen synthesis
Angiogenesis or neovascularization
− New blood vessels − Edema as result of vasodilation and increased permeability New leaky blood vessels − ECM Structural ECM-vessel sprouting Non-structural-facilitate cell migration
Scar formation
Granulation tissue: Soft pink, vascular Scar: Pale, avascular
• Inactive spindle shaped fibroblasts
• Dense collagen
• ECM components
• Vascular regression, no longer required die by apoptosis through growth signals-no longer required to facilitate the repair process
Describe migration and proliferation
steps of repair
• Recruitment and proliferation of fibroblasts
− Fibroblasts migrate towards the site of injury
− Proliferation in response to growth factors and cytokines
• Released by M2 macrophages
− Repair begins when macrophages predominate at the site of injury following acute inflammation
Cutaneous wound healing
Healing by first intention
Thrombosis (scab)
Inflammation
^ 24 hours
Regeneration 3-7 days M2 Macrophages
Granulation tissue
Scar formulation
Cutaneous wound healing
Healing by second intention
Contraction
Myofibroblasts
larger clot, more inflammation & granulation tissue
Factors affecting repair
LFP MIN
Location
Foreign bodies
Poor perfusion
Mechanical
Infection
Nutrition: vic for collagen synthesis
Complications of healing
E F suck Exuberant granulation-excessive granulation tissue Fibrosis Splitting-Wound Dehiscence Ulceration Contraction Keloid formation-excess scar tissue
