Wound healing - Tesse Flashcards
Explain the role of skin
- structure and protection
- homeostasis and regulation
- sensation
What are two examples of abnormal response to skin wounding
ulceration, excess scar
what are normal responses to wounds
epidermal barrier restoration (epithelialization) and dermal barrier restoration (fibroblast proliferation)
What are the 4 stages of wound healing
- inflammation
- debridement
- repair
- maturation
What is the first stage of wound healin
inflammation
- early/vascular
-late/cellular
what is the second stage of wound healing
debridement
what is the third stage of wound healing
repair
- fibroplasia
- angiogenesis
-epithelialization
-contraction
What is the fourth stage of wound healing
maturation
-tissue remodelling
What stage of wound healing is medical intervention most effective?
inflammatory stage
how long is the inflammatory stage
0-3 days
what are the two phases of inflammatory stage
Vascular and cellular
Describe the vascular phase of the inflammatory response
- bleeding to clean wound bed
- immediate vasoconstriction (epinephrine response, vascular smooth muscle response)
- vasodilation ( 5 -10 minutes later, leakage of fibrinogen and clotting factors, cellular infiltration begins)
describe the cellular phase of the inflammatory response
-clot formation and establishment of scaffold
- fibrinogen > fibrin
- fibrin and plasmin plug lymphatics
- clot dries into a scab
what initiates stage 2 of wound repair
WBCs under scab
When does debridement start?
6 hours after wounding, peaks around day 2-3
What are the first responders to the scene during debridement
Neutrophils
what enzymes do neutrophils release during debridement
collagenase and elastase
what do neutrophils release to attract monocytes and fibroblasts
chemoattractant cytokines
which are essential to non-infected wounds: neutrophils or monocytes
monocytes
when do monocytes arrive?
12 hours in
what are three things that monocytes are essential for during debridement
- collagenase production
- phagocytic actions
- release growth factors and cytokines
Cellular infiltration begins during
debridement stage
what stage does exudate arise
debridement
What calls in the mesenchymal monocytes and keratinocytes that results in epithelialization
macrophages
What is “PRP”
platelet-rich plasma that can be injected into a patient to enhance wound healing
when do lymphocytes come into play
approx 1 week after wounding. Less numerous than macrophages.
what makes up wound exudate
dead cells, wbcs, tissue, protein, fluid.
When does the repair stage begin
day 3-5
what stage does proliferation of new tissue start
repair stage
what are four things that happen during stage 3 of wound repair
- fibroplasia (fibroblast proliferation)
- angiogenesis
- epithelialization
- wound contraction by development of myofibroblasts
When does fibroplasia begin
starts day 3-4, continues for 2-4 weeks
Describe fibroplasia
fibroblasts migrate from surrounding tissue. Mesenchymal cells proliferate in wound and migrate along fibrin strands in clot. Fibroblasts become myofibroblasts, develop cytoskeletal contractile elements. wound fibroblasts produce type 3 collagen, type 1 pro-collagen, ECM components.
What is the end result of fibroplasia
the fibrin filled wound becomes a connective tissue filled wound
Describe angiogenesis
new capillaries grow into wound, attracted by tissue hypoxia.
T/F: granulation tissue is low in blood flow, but high in innervation
false. it is high in blood flow, low in innervation.
What is granulation tissue
healing tissue composed of newly vascularized ECM, inflammatory cells, fibroblasts, matrix components
what are the five processes that occur during the repair stage
- fibroplasia
- angiogenesis
- granulation tissue formation
- epithelialization
- contraction
what are some purposes of granulation tissue
- resistant to infection
- provides surface for epithelial migration
- role in wound contracture
what type of collagen is most common in wounds
type 3
What is “proud flesh”
excessive granulation tissue that becomes irregular, grows above skin edge, and interferes with contraction and epithelialization
where does epithelialization begin
at the wound margin. requires granulation surface in open wounds. Stops with contact inhibition
what heals faster: a dry wound or a moist wound? Why?
a moist wound. This is because O2 is more available. Moist wounds heal 50% faster
What is contraction simultaneous with
granulation and epithelialization
what changes phenotype during contraction phase?
fibroblasts become myofibroblasts so that they can contract
what is myofibroblast persistence?
pathologic tissue development, excessive contracture, fibrosis, disfigurement
what are the three phases of wound contraction
- lag phase
- rapid contraction phase
- slow contraction phase
what is the lag phase of wound contraction
wound increases in size due to swelling, movement, etc. lasts 5-10 days
how long does the rapid contraction phase last
10-14 days
what is the slow contraction phase
follows complete epithelialization. gradual change of myofibroblasts returning to fibroblasts. begins after 2+ weeks
The only layer contracting during the wound contraction phase is the
epidermis, NOT the dermis. adnexal structures therefore do NOT return, as they are part of the dermis.
what is contact inhibition
growth of cells until they touch another cell
What is involved with the maturation stage of wound healing
deposition, reorganization, and rearrangement of collagen fibers. The cell population matures, so myofibroblasts revert to normal fibroblasts.
maturation changes the ___
ECM. Type 3 collagen is replaced by type 1, increased cross-linking, and reorganization along lines of tension
T/F: the gain in mechanical strength of tissue during maturation is slow
true. most rapid between 7-14 days, 20% normal at 3 weeks, and 80-85% of normal at final result. will never return to original tensile strength of uninjured tissue.
