Flashcards in healing and repair Deck (14):
What could be the three outcomes from injury?
1. Healing - the formation of scar tissue
2. Regeneration - growth of cells to replace lost structures, which requires an intact tissue scaffold and appropriate stem cells to be intact
3. Fibrosis - laying down of fibrous scar tissue well outside of the original injury boundaries
what are the 4 ECM proteins?
collagen, elastic fibres, adhesion proteins and proteoglycans
when can granulation tissue start to form?
24 hours after injury
what are the major source of ECM components?
degradation of ECM is performed by what ?
MMPs: matrix metalloproteins, which are made by fibroblasts, macrophages and neutrophils. MMPs are regulated by TIMPs - tissue inhibitors of metalloproteinases
Describe healing by first intention
There is limited death of epithelial and connective tissue.
-narrow incisions with blood cells and fibrin present - there's a scab cap
- Neutrophils appear at margin with 24 hours, epithelial cells deposit a new basement membrane 24-48 hours.
-Neutrophils are replaced by macrophages by 3 days and the space is filled with granulation tissue, vertical collagen fibres not organised, vascularisation proceeds and collagen becomes reorganised, scarring is minimal
Describe healing by second intention
more cellular loss, edges not opposed, more abundant granulation tissue, and more necrosis debris and exudate leading to more severe inflammation
-wound contraction reduces size of scar, myofibroblasts contains actin filaments cause contraction
-The dermis ends up thin
What are the factors that affect healing?
injury related (nature of tissue), inflammatory factors (foreign bodies), host factors (age, anaemia)
What is the key growth factors in angiogenesis?
The vascular endothelial growth factor
What do macrophages do microscopically in healing?
Secrete growth factors, which attract fibroblasts, which then begin to proliferate
Describe granulation tissues structure once it becomes a scar?
Spindle shaped fibroblasts, dense collagen, elastic tissue fragments
What are two complications from healing?
Deficient scar formation causing mechanical stress and leading to ulceration
Excessive formation of repair components that leads to raised scars (excess collagen), or keloids (scars beyond original boundary)
Give the 7 step of healing
1. Inflammation to remove damaged and dead tissue
2. Entry and proliferation of parenchymal cells and production of new connective tissue
3. Formation of new blood vessels
4. Synthesis of new ECM proteins
5. Tissue remodelling
6. Wound contraction
7. Acquisition of wound strength