Healing Flashcards
What is wound healing?
body’s replacement of destroyed tissue by living tissue.
What are the causes of tissue destruction?
- Traumatic excision
- Physical, chemical & microbial agents
- Ischaemia which leads to infarction
- Hypersensitivity reactions
What is the initial stage of healing?
CONTRACTION: mechanical reduction in size of defect occurring in the first few weeks.
- caused by general remodelling of granulation tissue not shortening of cells/fibres
- initial 2-3 days = rapid contraction
- reduce in wound size 80%
How does contraction increase the speed of healing?
Smaller defect means less tissue needs to be formed.
What are the ways lost tissues can be replaced?
- Repair
- Regeneration
- Reconstitution
How is tissue replaced by repair?
- replaced by granulation tissue
- matures to form scar tissue
- inevitable when surrounding specialised cells do not have capacity to proliferate.
(e. g. muscles & neurons)
How does tissue replacement by regeneration occur?
Replacement of lost tissues by tissue similar in type
- proliferation of surrounding undamaged specialised cells
- occurs when cells compromising tissue are capable of muliplying
(e. g. liver)
How does replacement of tissue by reconstitution occur?
co-ordinated regeneration of several types of tissue
- result in reformation of whole organs
e. g. liver following partial hepatectomy.
What is organisation of tissues?
Replacement of necrotic tissue, fibrin, and blood clot by living granulation tissue
What phases occur during the growth of granulation tissue?
- Blood clot forms
- Acute inflammation occurs
- Demolition of clot with new growth occuring underneath
- Granulation tissue forms by proliferation and migration of surrounding connective tissue elements (capillary loops, fibroblasts & inflammatory cells)
How does the tensile strength of the wound change during healing?
- Initially low (only fibrin holds the cut edges-may require sutures)
- Increases as collagen forms
Name 2 ways skin wounds can heal:
- Primary intention (clean cut)
- Secondary intention (open wound)
Dependent on wound type
How do wounds heal via primary intention?
Wound contraction
- wound fills with clot
- epithelium migrates over wound
- epithelial spurs are formed
- granulation tissue formation proceeds
- scar tissue remains
How does healing by secondary intention occur?
Blood clots in large wound
- wound contraction
- Granulation tissue proceeds as clot gets smaller as socket heals from base upwards & epithelium proliferates from stratum germinativum down the wall of the wound
- epithelium continues to fill in the wound (get closer to surface)
- blood clot scabs off
- organisation of granulation tissue occurs
- stratified squamous epithelium heals without visible scar
Name reasons why healing may be delayed:
- Poor blood supply (age/ med condition)
- Presence of infection / foreign body
- Excessive movement
- Age
- Nutrition (lack of protein = defiicent collagen formation/ vitamin C = formation of weak granulation tissue
- Temperature
- Great degree of specialisation
- Organs less liable to injury heal slower
