Pathology Week 5 E Flashcards
Define resolution:
The healing outcome in which a tissue is restored to its pre injury state
What 3 events usually occur during resolution?
Liquefaction
Removal of products of liquefaction
Removal of remaining particulate matter
When does resolution occur?
When only a few cells are lost/ only a small injury
When does regeneration occur? How does it occur?
When there is extensive cellular damage
It occurs with the replacement of lost cells
What must happen before regeneration can occur?
The site of trauma must be cleared
What are labile cells? Example.
Cells which divide actively throughout life, replacing cells which are normally lost. Eg. Skin cells
What are stable cells? Example. What do they require for regeneration?
Cells with a long life span and low rate of division. They are mature, differentiated, functioning cells.Found in areas such as liver and pancreas.Need an adequate connective tissue framework for regeneration
What are permanent cells? Example.
Have no capacity for mitotic division in post natal life.Eg. Neurons, myocardial cells
What is primary intention healing?
A healing process which occurs when a small number of cells is lost
What is secondary intention healing?
A healing process which occurs when a large number of cells is lost
What are the 2 phases of primary intention healing?
Preparative phase
Reparative phase
What happens in the preparative phase of primary intention healing? What are the events?
The wound is stabilised.
The events are:
- wound defect is filled with blood
- acute inflammation
- bleeding is arrested (platelets, clotting proteins)
- scab formation
- clot retraction draws the edges of the wound together.
What is the purpose of a scab? 5 P’s
Prevents further blood loss
Pulls wound edges together
Prevents dehydration
Prevents entry of micro organisms
Protection against physical irritation
What can fibronectin bind to?
Collagen
Fibrin/fibrinogen
Proteoglycan
Cell surfaces
Bacteria
What are the events that occur in the epidermis in the reparative phase of primary intention healing?
Increased mitosis and budding of basal cells resulting in bridging of wound deficit.Growth and migration of local epithelial cells help to fill tissue deficit and restore epithelial continuity
If damage to the basal layer was minimal then epithelial architecture is normal
What are the events that occur in the epidermis in the reparative stage of primary intention healing?
- Migration and division of fibroblasts
- Invasion of wound by fibroblasts
- Collagen synthesis and deposition by fibroblasts
- Gradual strengthening (maturation) of scar tissue (eg collagen cross linking)
What is difference between the preparative phases of primary and second intention healing?
Nothing except that the process in secondary intention healing is much more extensive, intense and longer lasting
In the reparative phase of secondary intention healing what are the events that occur in the epidermis?
Restoration of epithelial continuity is initially not possible as the tissue deficit cannot be bridged by cellular budding (bridge formation). Also no formation exists for epithelial cells to migrate over.
In the reparative phase of secondary intention healing what are the events that occur in the dermis?
- Development of granulation tissue
- Gradual strengthening of scar tissue
- Granulation tissue serves as a foundation for the spread of epithelial cells but loss of normal epidermal architecture results at the site of healing. Thus skin overlying the scar does not look normal
- Scar devascularisation occurs (scar colour changes from pink to white)
What are the events of granulation tissue formation?
1- migration and division of fibroblasts
2- invasion of wound defect by fibroblasts
3- invasion of wound defect by capillaries
4- collagen synthesis and deposition by fibroblasts
What are the events of strengthening of scar tissues?
1- collagen cross-linking
2- type I collagen replaces type II
3- alignment of collagen fibres along stress lines
4- achievement of maximum scar strength in approximately 6 months.
What are the main contributors to wound contraction?
Collagen
Myofibroblasts
What are myofibroblasts? What do they do?
Specialised myofibrils containing fibroblasts
Undergo contraction of actomyosin filaments early in wound contraction
Cause early contraction of wound
What are the effects of collagen cross linking and condensation?
Wound contraction
Increased tensile strength and flexibility of scar
What are factors which impede healing?
- Ongoing infection
- Clotting abnormalities
- Poor overall health status
- Suppressed immunity
- Mechanical irritation
- Poor blood supply
- Inadequate nutrition
Summary of events in secondary intention healing:
- Bleeding
- Clot and scab formation
- Intense inflammatory/ exudative phase
- Restoration of epithelial continuity cannot occur as it needs a foundation to grow across
- Granulation tissue develops
- Progressive collagen deposition, devascularisation and wound contraction.
- Scar tissue maturation
Define contractures
When tissues surrounding a large wound are mobile and are gradually drawn in by the contracting scar
