Basic Wound Healing Flashcards
(53 cards)
1
Q
rule of basic wound healing?
A
In any given situation, the appropriate action is determined by the subsequent sequence of events
2
Q
what are the phases of wound healing?
A
- inflammation phase which includes the acute vascular phase
- debridement phase
- repair phase
- maturation phase
3
Q
When does the inflammation phase occur?
A
immediately
4
Q
What is included in the acute vascular phase?
A
- hemorrhage
- vasoconstriction (for immediate homeostasis, occurs in less than 10 mins)
- endothelial injury starts the clotting cascade
- cellular adhesion (involving leukocytes, platelets, & RBC)
- coagulation
5
Q
Who are the cellular players of the inflammation phase?
A
- mast cells, macrophages, platelets, growth factors or cytokines (initiate & maintain the proliferative phase of healing)
- this begins immediately after injury & lasts about 5 days
- WBC (neutrophils, eosinophils, basophils) - initiate debridement phase
6
Q
What are the vasoactive substances?
A
- histamine (for an early increase in permeability, subside w/in 30 mins)
- serotonin (causes endothelial cells to swell & induces lysyl oxidase)
- kinins
- chemotactic agents (prostaglandins & cytokines)
7
Q
What do prostaglandins do?
A
- permeability changes, vasoactive, chemotaxis, stimulate mitosis
8
Q
What is the local effect of these vasoactive substances?
A
- vasodilation, leakage, blocked lymphatics -> leads to the classic signs of inflammation
9
Q
What are the classic signs of inflammation?
A
- redness, heat, swelling, pain
10
Q
Important things about granulocytes?
A
- pH sensitive (environment of wound impacts WBCs that enter the wound)
- antibacterial
- collagenase (break down collagen so can be replaced w/ the tissue that is normally there)
- proteolytic enzymes (breakdown cells that are no longer needed/debridement)
11
Q
what do macrophages do at the wound site?
A
- custodial stuff, mitogenic factors, called in by cytokine signaling?(TGFalpha, TGFbeta, IGF-1)
12
Q
when does the debridement phase occur?
A
6-12 hrs after injury (overlaps w/ the inflammatory stage)
13
Q
What is the chemoattractant?
A
purulent material w/ neutrophils & monocytes
14
Q
What is the exudate made of?
A
WBC, dead tissue, wound fluid
15
Q
what do neutrophils do in the debridement phase?
A
- increase for 2-3 days, prevent infection, phagocytize organisms & debris, then degenerate: bursting open & releasing enzymes.
- these enzymes breakdown bacteria, extracellular debris, & necrotic material, & stimulate monocytes
16
Q
Which cells are essential for wound healing? Which are not?
A
monocytes are; neutrophils are not
- healing is severely impaired when macrophage function is suppressed, but neutropenia or lymphopenia dont inhibit healing or development of wound tensile strength
17
Q
What do monocytes do in the debridement phase?
A
- major secretory cells that synthesize growth factors for tissue formation & remodeling
- become macrophages in the wound in 24-48hr
- secrete collagenases (remove necrotic tissue, bacteria, & growth factors)
- secrete chemotactic & growth factors
- recruit mesenchymal cells
- stimulate angiogenesis
- modulate matrix production
18
Q
what do lymphocytes do in the debridement phase?
A
- they appear later than neutrophils or monocytes
- secrete soluble factors which stimulate or inhibit migration & protein synthesis by other cells
19
Q
When does the repair stage of wound healing occur?
A
3-4 days after injury, overlapping w/ the debridement phase
20
Q
How are fibroblasts involved in wound healing?
A
- transforming growth factor produces fibronectin (initiating cell binding & fibroblast movement)
- platelet derived growth factor & basic fibroblast growth factor
- originate from undifferentiated mesenchymal cells -> migrate to wounds along fibrin strands in fibrin clot -> just before new capillary buds as inflammatory phase subsides
- synthesize & deposit collagen, elastin, & proteoglycans (fibrous tissue)
- haphazard orientation until day 5 - > then tension causes fibroblasts, fibers, & capillaries to orient parallel
- fibrin disappears & collagen is deposited which increases tensile strength
21
Q
What does collagen do in the repair phase?
A
- wound tensile strength (not as much as the original tissue)
- wound maturation (Type I increases (more organized & functional - mature) & Type III decreases - immature)
- increased collagen leads to decreased fibroblasts (ends the repair stage)
22
Q
When is maximum collagen?
A
2-3 wks post injury
23
Q
What happens in the repair stage if there are no macrophages?
A
- delay in fibroblast migration & proliferation, collagen production, & capillary ingrowth
24
Q
What happens during angiogenesis?
A
- capillaries invade the wound behind migrating fibroblasts (fibroblasts are required for angiogenesis)
- interaction of the extracellular matrix with cytokines (migration & proliferation of endothelial cells)
- new capillaries, fibroblasts & fibrous tissue form bright red, fleshy granulation tissue 3-5 day after injury
25
How old is this wound?
nice healthy edges (granulation tissue) allow us to know that this wound is from at least 3 days ago
26
What does granulation tissue do?
- fills defects & protects wounds, a barrier for infection, surface for epithelial migration
- source of special fibroblasts called myofibroblasts
27
What do myofibroblasts do?
- wound contraction (using actin & myosin they pull the edges of the skin closer together to decrease the size of the wound > then endothelial cells dont have to migrate as far)
28
Where are myofibroblasts not found?
- normal tissue, incised & coapted wounds, or tissues surrounding contracting wounds
29
How quickly is granulation tissue formed?
formed at the edge of the wound at a rate of 0.4-1 mm/day
30
When does epithelialization occur?
- 24-48hrs in sutured wounds (1st intention healing b/c skin is in apposition)
- 4-5 days in open wounds once granulation bed has formed (second intention healing)
31
First intention healing vs second intention healing?
- 1st: sutured incision, tissue apposition w/ no granulation bed
- 2nd: open wound healing w/ granulation, contraction, & epithelialization
32
Why is covering a wound a balance?
- cover too long: the pressure of the bandages lowers the oxygen tension in the tissue, delaying the epithelialization process, & causing exuberant degranulation
- cover not long enough: wound gets crusty making it hard for collagenases to break down the tissue & epithelial cells to migrate
33
what is epithelialization guided by?
collagen fibers
34
What do basal cells at the wound edges do during epithelialization?
- have microvilli & extend their broad pseuopodia over the exposed surface of collagen bundles
- epithelial cells migrate over these until they contact the wound surface
- they produce collagenases to dissolve scabs
35
What happens during epithelialization?
- migration of epithelial cells over the basal cell pseudopodia until they contact the wound surface
- contact w/ epithelial cells on all sides inhibit further cell migration
- only 1 cell layer thick at first but thickens as new layers are added
36
What can happen when epithelialization occurs along suture tracts?
- foreign body reaction, sterile abscess, &/or scarring
- minimized by early suture removal
37
when is epithelialization visible?
4-5 days after injury
38
What helps epithelialization?
a moist environment
39
Where does epithelialization not occur?
over non-viable tissue
40
What is epithelialization dependent on?
energy dependent & related to oxygen tension (amount of oxygen in the tissue)
41
What does anoxia prevent during epithelialization?
epithelial migration & mitosis
42
What happens during wound contraction?
- reduces the size of wounds following fibroblasts, reorganization of the collagen in granulation tissue, & myofibroblasts perform contract a wound edges
43
Wound contraction is...
centripetal meaning the full-thickness skin edges are pulled inward
44
How quickly does wound contraction occur?
0.6 to 0.8 mm/day
45
What does wound contraction occur independently of & simultaneously with?
- independent of epithelialization
- simultaneously with epithelialization & granulation
46
What causes wound contraction to stop?
- wound edges meet, tension is excessive, or the myofibroblasts are inadequate
47
When are wounds noticeably smaller by?
5-9 days
48
When does the maturation phase of wound healing occur?
17-20 days (collagen has been adequately deposited) to years (may continue for years)
49
What happens during maturation phase?
- functionally oriented fibers become thicker
- Type III collagen decreases & Type I increases
50
How does wound strength change during maturation?
- it slowly increases but will never regain normal tissue strength (80% may be regained)
- most rapid gain in strength is 7-14 days after injury when collagen rapidly accumulates
- 20% gained in the 1st 3 weeks after injury
51
Systemic factors affecting wound healing?
- age (older patients)
- nutrition (malnourished/low protein OR obesity)
- concurrent disease (hyperadrenocorticism, DM, hepatic disease, uremia)
- corticosteroids
- NSAIDs
- immunosuppression
52
Surgeon factors affecting wound healing?
- tissue handling, procedure duration, suture material, suture tension, hematoma, seroma
53
wound environment factors affecting wound healing?
- infection, foreign body
- microenvironment needs appropriate oxygen tension, temperature, pH, & topical meds
