Wound Healing Physiology Flashcards
Acute wound vs. Chronic Wound
Acute wound progresses through normal stages of healing and achieves closure in a timely manner.
- Within 2 weeks
Chronic wound fails to progress through normal stages of healing within the expected time frame.
- Within 30 days
What are the three types of wounds based on depth of tissue involvement?
- Superficial: Effects epidermis only
- Abrasions, sunburn or flash burn without blistering.
- Partial-thickness: Effects epidermis and extends into the dermis, heals primarily by re-epithelialization from wound edges and dermal appendages
- Includes blisters which disrupt the basement membrane that separates the epidermis from the dermis
- Full-thickness wounds: Extends through the epidermis and dermis into the subcutaneous layer or deeper.
- Full thickness and subdermal burns
- Stage 3 & 4 pressure ulcers
- Wagner grade 2-5 neuropathic ulcers
- Deep wound: ?
What is a superficial wound?
A wound affecting only the epidermis, such as abrasions or sunburns.
What is a partial-thickness wound?
A wound extending into the dermis, healing primarily by re-epithelialization.
What is a full-thickness wound?
A wound that extends through the dermis into the subcutaneous layer or deeper.
What is primary intention wound closure?
- Wound edges are approximated and closed
- Typically healing in 1-14 days
What is secondary intention wound closure?
The wound heals by forming granulation tissue, followed by epithelialization.
What is tertiary intention wound closure?
Delayed primary closure, allowing initial healing followed by suturing after infection resolution.
What are the four phases of wound healing?
- Hemostasis
- Inflammation
- Proliferation
- Remodeling
Hemostasis
- What happens?
- What role do platelets play in wound healing?
- Hemostasis: Vasoconstriction, platelet aggregation, and clot formation occur immediately after injury.
- Platelets release growth factors and cytokines, initiating the healing process.
When does the inflammatory phase start?
The inflammatory phase starts at the time of injury and lasts 3-7 days.
What are the cardinal signs of inflammation?
- swelling
- redness
- warmth
- pain
- decreased function
What cells are primarily involved in the inflammatory phase?
- platelets
- neutrophils
- macrophages
- fibroblasts
- mast cells
What is the role of neutrophils in wound healing?
- They cleanse the wound of microorganisms and debris, initiating the immune response.
- Neutrophils levels peak at 24 to 48 hours after injury (acute response) to clean wound site for tissue restoration.
What is the goal of the proliferative phase?
To fill the wound defect with new tissue and restore skin integrity.
What is angiogenesis?
The formation of new blood vessels, occurring during the proliferative phase.
What cells produce granulation tissue?
Fibroblasts produce granulation tissue by synthesizing collagen.
What is wound contraction?
Reduction of wound size due to myofibroblasts pulling the edges together.
When does re-epithelialization occur?
It starts immediately after trauma and continues until the wound is resurfaced.
What is the remodeling phase?
The phase where collagen is reorganized, lasting up to 2 years post-injury.
What is the maximum tensile strength achieved during remodeling?
Scar tissue achieves 70-80% of the original tissue’s tensile strength.
What are polymorphonuclear leukocytes (PMNs)?
A group of white blood cells involved in the inflammatory phase, including:
- neutrophils:
- eosinophils: motile phagocytes that have a distinctive anti-parasitic function.
- basophils: release histamine, promoting vasodilation and increased blood flow.
- macrophages: clean debris, release growth factors, and transition the wound to the proliferative phase.
What is the function of basophils?
Basophils release histamine, promoting vasodilation and increased blood flow.
What are fibroblasts?
Cells that synthesize collagen and extracellular matrix components during the proliferative phase.
What role do keratinocytes play in wound healing?
Keratinocytes migrate from wound edges to re-epithelialize the wound.
What is granulation tissue?
New connective tissue with capillaries that forms during the proliferative phase.
What is matrix metalloprotease (MMP) function?
MMPs degrade extracellular matrix to allow cell migration, but excess can prolong inflammation.
What are tissue inhibitors of metalloproteases (TIMPs)?
Proteins that regulate MMP activity, balancing collagen synthesis and degradation.
What is autolytic debridement?
The process where macrophages release collagenases to clear necrotic tissue.
What is epithelialization?
The formation of a new epithelial layer over the wound.
What is hypogranulation?
Insufficient granulation tissue formation, resulting in an unfilled wound defect.
What is hypergranulation?
Excessive granulation tissue that extends above the wound edges.
What are hypertrophic scars?
Raised, red scars caused by excessive collagen deposition within the wound border.
What are keloids?
Overgrowth of scar tissue that extends beyond the original wound border.
What is a contracture?
Rigid scar tissue that limits joint range of motion.
What is dehiscence?
Rupture of a wound along a surgical incision.
What factors contribute to chronic inflammation?
- foreign bodies
- repetitive trauma, and
- cytotoxic agents can prolong inflammation.
What is epibole?
Rolled wound edges that prevent epithelial migration and wound closure.
How does prednisone affect wound healing?
It inhibits inflammation, granulation, contraction, and collagen production.
What is the impact of immune suppression on healing?
Impaired immune function can delay or prevent wound healing.
How does bioburden affect wound healing?
Presence of necrotic tissue and bacteria can prolong inflammation and prevent closure.
What role do cytokines play in wound healing?
Cytokines mediate cell communication and can be pro- or anti-inflammatory.
What is arrested epithelialization?
The halting of epithelial migration, often due to rolled wound edges or infection.
What are senescent cells?
Cells that have stopped dividing and contribute to delayed wound healing.
What is the goal of wound healing by tertiary intention?
To manage infection before final wound closure by suturing.
What is wound closure in the remodeling phase?
Final reorganization of collagen to strengthen the wound.
What is the role of integrins in wound contraction?
Integrins facilitate the contractile activity of fibroblasts and myofibroblasts.
What is heparin’s role in the inflammatory phase?
Heparin stimulates endothelial cell migration and promotes capillary formation.
