Wound healing and repair Flashcards
what are classifications of cell types?
- labile -multiply continually throughout life e.g. bone marrow
- Stable - only multiply when receive stimulus to do so)
- Permanent - cannot multiply
what is restitution?
Restitution means the complete restoration of the tissues to normal after an episode of acute inflammation
what factors favour restitution?
- Minimal cell death and tissue damage
- Occurrence in an organ or tissue with regenerative capacity eg liver
- Rapid destruction of the causal agent
- Rapid removal of fluid and debris by good local vascular drainage
what is needed for complete repair (restitution)?
-Labile and stable cell populations
-Death of permanent cell populations must be repaired with scar
tissue formation
-Tissue architecture must be preserved
what does repair by connective tissue fibrosis involve?
- Angiogenesis- formation of new blood vessels
- Migration and proliferation of fibroblasts
- Deposition of collagen
- Maturation and organisation of fibrous tissue - remodelling
what is organisation of tissues and what factors favour organisation?
Organisation of tissues is their replacement by granulation tissue
• Large amounts of fibrin formed
• Substantial necrosis
• Exudate and debris cannot be removed or discharged
what happens during organisation?
Much skin is completely destroyed and the underlying tissue is undergoing repair
The damaged area is being replaced by vascular granulation tissue
what is angiogenesis critical to?
i) Chronic inflammation and fibrosis
ii) Tumour cell growth
iii) Formation of collateral circulation
what are the stages of organisation?
- angiogenesis
2.migration and proliferation of fibroblasts - deposition of collagen
- tissue remodelling/organisation
(look into more detail in slides)
Summarise wound healing..
Induction of acute inflammatory response
o Regeneration of parenchymal cells (if possible!)
o Migration and proliferation of parenchymal and connective tissue cells
o Synthesis of collagen
o Remodelling/organisation of connective tissue and parenchymal components
what is the difference between repair with scarring in the first intention and the second intention?
First intention - surgical scar -Closely apposed edges Minimal granulation tissue Minimal fibrosis
Second intention - ulcerated surface -Edges widely separated Prominent granulation tissue Prominent fibrosis
Describe healing by first intention.
- Limitedcelldeath
- Basementmembrane
disrupted - Incisional space fills with
blood - Scab forms
- Neutrophils move towards clot
- Theepidermisthickensatits cut edges
- Epidermalcellsmigratealong cut margins of dermis
- Epithelial cells fuse in the midline beneath the surface scab
- Day 3 neutrophils largely replaced by macrophages
- Day 5 granulation tissue invades incision space
- Collagen fibres bridge the incision
- Epidermis recovers two normal thickness
How is second intention different?
- Large defects involve more fibrin and more necrotic tissue therefore inflammatory reaction more intense
- Much larger amounts of granulation tissue
- Wound contraction plays an important role in reducing size of defect
what local factors influence wound healing?
Infection – single most important cause of delay in healing
- Mechanical factors – ie early motion of wounds delays healing
- Foreign bodies – ie sutures or glass
- Size, location and type of wound – wounds heal better in richly vascularised areas
what systemic factors influence wound healing?
Nutrition – wound healing profoundly influenced by ability to synthesise protein and collagen
- Metabolic status – diabetes is associated with delayed healing
- Circulatory status – an adequate vascular supply is essential for normal cellular function (hypoxia, reduced local nutrition)
- Hormones – glucocorticoids are anti-inflammatory but impair collagen synthesis
