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Phases of Wound Healing

Terms in this set (60)

Partial Thickness Wounding
Loss of epidermis and part of dermis
Loss of epidermis and part of dermis
What are Partial Thickness Wounds?
Full thickness Wound
Loss of Epidermis and dermis, extending into the subcutaneous tissue and in some cases involving bone, tendon, or muscle
Loss of Epidermis and dermis, extending into the subcutaneous tissue
What are Full thickness wounds?
papillary and reticular
What are the two layers of the dermis?
fibroblasts
The major cells responsible for skin renewal are the
papillary layer of dermis
Fibroblasts, mast cells, and macrophages, all necessary for skin renewal and regeneration, are located primarily in
reticular formation of dermal/epidermal junction
The primary characteristic of the skin that enables it to withstand friction and shear forces is:
Primary Intention
Types of Wnd Closure

When a clean surgical incision is created and the edges can be safely approximated and secured with sutures, staples, or surgical glue
Delayed Primary Intention
Types of Wnd Closure

Delayed closure until defect fills, edema resolves, bioburden resolves, or ready for skin graft
Wound is too big, swelling, and high bioburden.
What are some reasons that delayed primary intention may be chosen?
Secondary intention
Types of Wnd Closure

Left to close without surgical intervention; I&D, surgical dehiscense, etc
Secondary Intention
Types of Wnd Closure

What type of wound is this?
Superficial Partial Thickness closure
Types of Wnd Closure

Closes via Epithelial resurfacing
Superficial Partial Thickness Closure
Types of Wnd Closure

Closes via Epithelial resurfacing
Hemostasis, Inflammation, proliferation, and remodeling
What are the 4 stages of acute wound healing?
No
If a wound is bleeding does that mean it is full thickness?
Secondary Intention
Method of Closure of this wound?
Full Thickness
What type of wound is this?
Deep partial and full thickness wounds
All phases of healing happen in what type of wounds?
Epitheliziation
How do superficial and superficial partial thickness wounds heal?
Hemostasis
•Initial local small vessel vasoconstriction
•Vasodilation in adjoining vasculature = edema, warmth, erythema
•Activated platelets promote clumping = clot (small vessels, not arteries)
•Clot - fibrin mesh, platelets, embedded blood cells
•Chemical signals trigger migration of primary cells of inflammation
Neutrophils, Macrophages, and mast cells
What are the first cells of inflammation that arrive on the scene?
Neutrophils
Inflammation Cells

1st 24 hrs; peak ~48hrs "infantry soldiers"
•Chemotactic, phagocytic, secrete enzymes, proteases, etc. (MMPs - p. 28)
•Short life span (<24 hrs), #s decline as bacterial counts decline
•If present too long - can damage healthy tissue
Macrophages
Inflammation Cells

•- "big guns" "tanks"
•Secrete enzymes (collagenase), growth factors, etc.
•Phagocytic, chemotactic, promote angiogenesis
Mast Cells
•Degranulate
•Histamine - increases vascular dilation & permeability
•= edema & erythema
•Facilitates greater extravasation of Ns & Ms into the area
2-3 days
How long should inflammation last?
Primary intention
How is this closing?
MMPs
Enzymes that digest tissue. Normally we hae a good balance on how many _______are in a wound and how long they stay
TIMPs
They cause MMPs to go away. We want MMPs to be there in inflammatory phases but then as we leave inflammatory process to end we want more _______to balance out the degradation.
Angiogenesis, granulation formation, contraction, and epitheliization
4 Primary Events of Proliferation
Wound closure
Goal of Proliferation
Angiogenesis
Stages of Proliferation

•Directed by local ischemia, growth factors, chemical mediators, etc.
- Ensures endothelial cell migration that results in capillary sprouting
Granulation tissue formation (Fibroblasts)
Stages of Proliferation

•Temporary connective tissue latticework fills void
•Type III collagen (immature, unorganized)
•F lay down extracellular matrix (ECM) - scaffolding
•New capillaries migrate into scaffolding = red granular tissue
Fibroblasts
Cells that are the primary reason for granulation tissue:
Full thickness wounds
What type of wounds is Contraction greatest in?
Contraction
Stages of Proliferation

◦Maximally present ~ days 10-20 post insult
◦Begin ~1 week post wounding
◦Pull wnd surfaces together to minimize open area
◦Greatest in full thickness wnds
Fastest in linear; slowest in circular
Fastest in linear; slowest in circular
What type of wounds is Contraction fastest and slowest in?
1 week post wounding
Normally, how fast does Contraction start?
Myofibroblasts
What type of cells are involved in Contraction?
Epithelialization
Stages of Proliferation

◦Epithelial cells at edges (basal layer) flatten, sense environment, & advance
◦Over healthy dermis or granulation tissue
◦Can stall/slow down secondary to impairments:
Stratum basal
Where do epithelial cells come from?
Epithelialization
What phase of Proliferation is happening here?
15
•Brand new epithelium is ~___% as strong as normal skin
Dirty/scabby edges, nonviable tissue, open space, and bone
What things can slow down epithelialization?
Proliferation (granulation, contraction & epitheliazation) and Remodeling
What Phase of Healing is this wound in?
Dehiscence
Gap of split wound > 1 cm
Separated
Gap of split wound < 1 cm
As we cut down on blood flow we are not laying down type 1 collagen (oxygen depdent). MMPs don't care about oxygen so they breakdown type 3 collagen. You are left with less thick scars and cuts down on discoloration.
Synthesis is O2 dependent, lysis is not - why is this important?
MMPs
- assist in breakdown of disorganized, immature collagen
Collagen Synthesis and lysis
How can you tell if a scar is still remodeling
With granulation tissue from the bottom up. Put dressing material inside the tube so that when you move around it won't squeeze and leave pockets.
How do sinus tracts fill up?
Facilitates autolytic debridement, reduces scarring, faster closing, promotes collagen synthesis, growth factors, and re-epithelialization.
Benefits of Moist Wound Healing
It won't attach to bone or tendon
Why do you have to put a skin graft over granulation tissue?
10 to 21 days post wounding
Myofibroblasts are maximally present in the wound from:
Macrophages
Which one of the Primary cells of inflammation promotes angiogenesis?
Foreign bodies, repetitive mechanical trauma, high MMPs, and cytotoxic agents
What are 4 things that cause chronic inflammation?
Usually happens when epithelization cells get tired of waiting and start growing down the sides
Why would not likely see epibole (rolled edges) in an acute wound (3 days old)?
wound healing
Goal of maturation/remodeling phase is
80
Mature scar is ___% as strong as normal skin
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