Muscle Injury: Principles of Tissue Healing and Repair Flashcards
What are the 2 processes that occur to facilitate?
Regeneration and Repair
What is regeneration?
tissue is replaced by the formation of surrounding undamaged cells in a ‘like for like’ basis.
What is repair?
damaged tissue is replaced through granulation tissue to form mature scar tissue.
What are the 4 main phases of muscle healing?
1.Bleeding phase
2.Inflammation phase
3.Proliferation phase
4.Remodelling phase
What can affect muscle healing?
inadequate nutrition, persistent inflammation, excessive or insufficient movement and smoking can affect healing process and times
What is the normal quoted time for bleeding in muscle injury?
normal quoted time 6-8 hours but depends on tissue type and mechanism of injury
What type of injury would be more and less than the quoted time for bleeding?
-less vascular tissues such as ligaments will bleed less and for a shorter time
-crush injuriesto the highly vascular muscle tissue can bleed for up to 24 hours.
In the inflammatory phase, what does cell damage cause the release of?
-Cytokines
-Kinins
-Histamines
What are kinins important for?
Vasodilation (for more blood flow)
Stimulation of pain receptors
What are histamines important for?
Vasodilator
What is a consequence of the inflammatory phase due to the release of certain factors?
As a consequence we get redness and heat and hence increased nutrients and oxygen which increases metabolic rate of tissue cells and helps healing
What happens to capillaries during inflammatory phase and what does this result in?
Also capillaries become more permeable hence
-Oedema – hence more pain and swelling (which cause temporary loss of function)
-And more fibrin hence stronger plug
What happens to the level of white blood cells during the inflammation phase?
More white blood cell influx: neutrophils and monocytes (hence phagocytosis to clear cellular debris)
What are the key signs of inflammation?
Redness
Heat
Swelling
Pain
Loss of function
When does the proliferation phase start and how long may it last?
Starts as 24 hours post injury and can last 2-3 weeks or longer
What occurs in the proliferation phase?
Deposition of healing material – and clean up of damaged tissue
What are the 4 things that occur in proliferation phase?
- Fibroplasia
- Increase in extracellular collagen production
- Myofibroblasts
- Angiogenesis
What is fibroplasia?
fibrous tissue formation to provide early scaffolding in tissue
What happens when there’s an increase in extracellular collagen production?
Fibroblasts, cells which lay down early collagen (type 3 collagen) which is more elastic than type 1 (which is stronger). This provides strength and integrity and also the scaffolding for the next phase (remodelling phase).
What happens with myofibroblasts?
Fibroblasts change to myofibroblast phenotype which are thick protrusions that extend to wound edges and extracellular matrix and contracts – approximating and contract wound edges together (minimise scarring)
What is angiogenesis?
the formation of new blood vessels
How long does the remodelling phase last for?
Last weeks, months or years
What are the characteristics of remodelling phase?
maturation of collagen structure and arrangement occurs resulting in an organised and functional scar
What are the steps involved in the remodelling phase of muscle healing?
1.Orientation of collagen fibres
-Re-orientation of collagen fibres due to pressure from contraction
-Forced alignment of fibres back to original formation
2.Collagen deposition: type 1 replaces type 3 collagen
-Once scaffolding is established and approximation of wound edges we have type 1 to give more tensile strength
3. Capillaries diminish in number
-Healing process diminishes, hence less capillarisation hence less redness
-This can be bad for chronic injuries when wound hasn’t healed yet
4. Tensile strength increases.
Rehabilitation – functionality and consequence of collagen type 1
