wound healing Flashcards
skin protects against
UV
mechanical stress
chemicals
thermal insult
dehydration
pathogens
skin is used to sense
touch
pressure
heat
layers of skin
epidermis
dermis
hypodermis
the epidermis is ___ in origin
ectodermal
what cells make up the epidermis?
keratinocytes, langerhan cells and melanocytes
the thickness of the epidermis is inversely proportional to ___
hair covering
___ gives the epidermis a semi-permeable/protective barrier
keratin
which layer of the skin is avascular
epidermis
hair follicles, nails and sweat glands are in what part of the skin?
epidermis
invaginations of the epidermis into the dermis
dermis is composed largely of ___
dense irregular and loose connective tissue
collagen and elastic fiber
GAGs
what type of cells are found in the dermis
fibroblasts
adipocytes
vasculature and lymphatics
nerve endings
mast cells and histiocytes
hypodermis is made of ___ muscle
panniculus carnosus
where do you find the stratum adiposum subcutis
hypodermis
what are the 3 interconnected levels of cutaneous circulation
subdermal (subcutaneous plexus)- deep
cutaneous- middle
subpapillary- superficial
what is different between the blood supply for skin of a dog vs a primate
dermis supplied by parallel musculocutaneous arteries and veins
hypodermis supplied by direct cutaneous artery and vein
direct cutaneous artery and vein is found
superficial and deep to panniculus muscle and in the hypodermis of cats and dogs
the direct cutaneous artery and vein supply
the deep or subdermal plexus
superficial or deep to panniculus muscle
cutaneous plexus is found ___
in the dermis
formed from branches of the deep (subdermal plexus)
gives rise to the superficial plexus
___ is the major vascular network in skin of dogs and cats
deep/subdermal plexus
___ extends capillary loops to nourish the epidermis
superficial plexus
During dissection, to elevate the skin and preserve cutaneous vasculature, you must go between the ____ and the ___
subdermal plexus/ panniculus m.
underlying skeletal muscle
3 stages of healing
inflammation/debridement
repair / proliferation
maturation/ remodeling
Immediately after injury, ___ fills the wound and cleans the wound surface
hemorrhage
blood clot/ scab formation provides a ___, ___ wound edges and provides the substrate for ___
hemostatic plus, immediate barrier to infection and fluid loss
stabilizes wound edges
early reorganization of the wound (scaffold)
vascular phase initially starts with ___ then followed by ___ with recruitment of plasma and leukocytes
vasoconstriction
vasodilation
cellular/debridement phase starts ___ after injury
6ish hours
what cells in the cellular phase
lymphocytes and PMNs
monocytes/macrophages
platelets
mast cell and eosinophils
___ come during the inflammatory phase and concentrate at the site of injury to remove cellular debris and bacteria
lymphocytes and PMNs
what do macrophages do
eat cell debris
secrete chemoattractants and growth factors and cytokines (PDGF, VEGF)
___ induces vasoconstriction, platelet and neutrophil aggregation
Thromboxane A2
___ influence angiogenesis and fibroblast activity
mast cells
eosinophils mediate ___ and ___
angiogenesis and epithelial migration
___ is considered the lag phase of wound repair
initial (inflammation/debridement)
rapid increase in wound strength from collagen happens in the ____
first 3-5 days
3 main events of repair/proliferative phase
granulation tissue formation
wound contraction
epithelialization
granulation tissues appears ___ at a rate of ___
3-5 days post injury
0.4-1 mm per day
granulation tissue will help healing by ___
protect the wound, provide a barrier to infection and act as a scaffold for epithelial migration
fibroblast produce ECM in a process called ___
fibroplasia
fibroblasts come from ___
local and distant sites
(can be from bone marrow→ myeloid cells)
fibroblasts migrate along ___
fibrin strands
___ produce ECM and cytokines and growth factors
fibroblasts
fibrin, fibronectin and hyaluronic acid will facilitate aggregation and orientation of___ and ___
collagen
growth of capillary buds (neovascularization)
what type of collagen is laid down first?
type III, then replaced by type I
greatest accumulation of collagen occurs when in healing?
7-14 days post injury
which growth factor is important for angiogenesis initially?
bFGF (first 3 days)
VEGF more important 4-7 days
which growth factor is important for angiogenesis at 4-7 days
VEGF
bFGF - 1-3 days
___, ___ and ___ are important mediators for angiogensis
growth factors and cytokines (bFGF, VEGF)
low O2
high lactate
initially capillary loops are open but become ___
closed arcades
wound contraction happens ___ post injury
full thicken skin advanced (no new skin formed)
5-9 days post injury
tension and shape determine how well it can move
how does wound contraction happen
fibroblasts grab onto collagen and pull- consolidate collagen in the wound center
myofibroblast grab onto skin and contract pulling the skin with them
___ requires new skin synthesis by keratinocytes
wound epithelialization
Within 24 hours of wounding, ____ from the wound margins begin to cover the wound
keratinocytes
(wound epithelization)
what stage of wound healing requires more O2
wound epithelization
energy dependent and positively related to oxygen tension
wound epithelization is faster or slower under moist wound healing conditions
slower
wound epithelization advances from ____ structures in partial thickness wound
adnexal
contains stem cells that speed up healing
what happens during maturation and remodelling phase
scab sloughs
maturation of collagen fibers
remodellling
a wound will reach ___ % of its original strength
70-80
cats or dogs heal faster?
dogs - will have more granulation tissue, greater wound epithelialization and wound contraction
ponies or horses heal better?
ponies
horses lead to proud flesh (EGT- exuberant granulation tissue)
contracture
contraction that results in problem
closes off opening or can’t move
5 wound assessment
type of ___
___of wound
degree of ___
tissue ___
___ of wound
type of trauma
age of wound
degree of contamination
tissue viability
location of wound
a clean wound
controlled aseptic environment
surgical incision
clean contaminated wound
contaminated area entered but no spillage
example: enterotomy
contaminated wound
most common
road rash, traumatic wound
acute inflammation with NO pus
dirty wound
pus, abscess, delayed treatment of traumatic wound
Contaminated wounds must be converted into ___ prior to closure (if immediate closure is not possible, open wound management will be necessary)
clean wounds -> surgical incision
___ will remove foreign debris and contaminants with large volume of warm fluids
lavage- hydrodynamic debridement
___ are used for lavage
balanced electrolyte solution
sterile saline
chlorhexidine (0.05%)
povidone- idodine (0.1-1%)
___ is accomplished by maintaining a moist wound environment
autolytic wound debridement
3 types of autolytic wound debridement
hydrophilic
occlusive
semiocclusive
exudate or wound fluid that contains enzymes and growth factors remain in contact with the wound
when a wound is too moist
maceration
___ are chemical enzymes that slough necrotic tissue
enzymatic wound debridement
can be nonselective
mechanical debridement
wet to dry
outdated
dries and rips off bad tissue
___ combines mechanical and autolytic debridement
hypertonic saline bandage
for moderate/high exudate, infected or necrotic wounds
maggot therapy
biosurgical debridement
removes necrotic tissue
systemic antimicrobials should be used ___
High risk of bacteremia or sepsis
* Prophylactic or therapeutic
* Prolonged use contraindicated
topical antimicrobials will enhance __ and may delay ___ formation
epithelization
granulation tissue
vacc bandage also called
negative pressure wound therapy
what do NPWT help with
negative pressure wound therapy (vacc bandage)
Decreases edema
* Decreases bacterial colonization
* Increases granulation tissue
* Increases local blood flow
* Enhanced epithelial migration
* Accelerates wound closure
when not to use a NPWT
negative pressure wound therapy
Malignancy in wound
– Untreated osteomyelitis
– Non-enteric or unexplored fistula
– Necrotic tissue with eschar present
– Exposed blood vessels or organs
4 types of moisture balancing dressings
calcium alginate- high exudate
polyurethane foam- moderate to high exudate
hydrocolloids- low to moderate
hydrogels- low to none
primary closure happens with in ___
24 hours
delayed primary closure happens within ___
2-5 days
before granulation tissue
secondary closure happens within
> 5 days, after granulation tissue
second intention healing
wound the healed on its own
Epidermis (ectodermal origin)
Composed of several layers of cells called___ that are undergoing a process of differentiation.
keratinocytes
The dermis is composed of ___, reticular (precollagen), and elastic fibers surrounded by a mucopolysaccharide ground substance (hyaluronic acid and chondroitin sulfate.
collagen
In dogs and cats, the hypodermis is made up of two distinct layers of fat (stratum adiposum subcutis) and ___
muscle (panniculus carnosus muscle).
This ___ is composed of the cutaneous trunci, platysma, sphincter coli superficialis, sphincter colli profundus, preputialis, and supramammarius muscles.
panniculus muscle
cutaneous circulation
Subdermal or subcutaneous plexus (Deep)-the major vascular network to the skin. In regions of skin where a panniculus muscle is present, the subdermal plexus lies both superficial and deep to it.
cutaneous (middle) plexus.
subpapillary (superficial) plexus which supplies the superficial dermis and extends capillary loops to nourish the epidermis (these loops are poorly developed in the dog and cats in comparison to primates and pigs).
In areas of the body where the panniculus is present, the surgeon must ___ to preserve the vital subdermal plexus.
undermine the fascial plane beneath the cutaneous musculature
