Acute and Chronic Wound Healing (Chapter 5) Flashcards
What are the four phases of the wound healing cascade?
- hemostasis
- inflammation
- proliferation/ repair
- remodeling/ maturation
How long is the process of wound healing?
Up to 18 months (1.5 years)
How does the hemostasis phase occur (3 steps)?
- Disruption of tissue (following injury) causes hemorrhage, exposing various blood components to the extracellular matrix (ECM).
- Platelets aggregate and degranulate, activating factor 12 (Hageman factor) which results in clot formation and hemostasis.
- Fibrinolysis simultaneously occurs to prevent clot extension and to dissolve the clot to allow for the next stage of healing.
How does the inflammatory phase begin?
As the fibrin clot is degraded, capillaries dilate and become permeable and the complement system is then activated which begins the inflammatory phase.
Which complement molecule is responsible for helping to bind neutrophils to bacteria (opsonization)?
C3b
What does the complement molecule C3b do during wound healing?
It helps to bind neutrophils to bacteria and facilitate phagocytosis and the subsequent bacterial destruction.
What are the two (2) main inflammatory cells?
Neutrophils and macrophages.
When do neutrophils peak within a wound?
In the first 24-48 hours.
When do macrophages appear within a wound?
Approximately 2-3 days after injury.
What are the main cellular sources of cytokines during wound healing (5)?
Platelets, monocytes, fibroblasts, macrophages and endothelial cells.
What is the role of cytokines during wound healing?
Cytokines regulate cell migration, proliferation, matrix synthesis, deposition and degradation and inflammatory responses in the repair process.
What is the timeline for the proliferation phase (start/finish)?
The proliferation phase usually begins 3 days after injury and lasts for several weeks.
What is the characteristic feature of the proliferation phase?
The formation of granulation tissue in the wound space.
Which type of collagen is laid down during the proliferation phase and why does this matter?
Type 3 collagen which has a weaker tensile strength than type 1 collagen and puts the patient at risk for wound dehiscence and evisceration, especially in the first 3 weeks.
When do fibroblasts appear in a wound?
Appear in large numbers within 3 days of injury and peak around the 7th day.
What is the role of fibroblasts in wound healing?
Fibroblasts synthesize and deposit extracellular proteins (which include collagen) and produce growth factors and angiogenic factors
What are the two main classes of ECM proteins and their subtypes?
- Fibrous proteins (collagen and elastin)
2. Adhesive proteins (laminin and fibronectin)
What are the four main events that occur during the proliferation phase?
- Granulation and scar formation
- Angiogenesis
- Epithelialization
- Wound contraction
