Integumentary System Flashcards
Factors considered when managing a wound
Type of injury, location, degree of contamination, age of the wound, blood supply, and skin lost
Types of vessels supplying the skin
Perforating musculocutaneous vessels pass through the muscle to supply skin
Direct cutaneous vessels run subdermally and parallel to the skin surface and closely associated with the panniculus muscle
The normal tension of the skin is the result of what
Elastic fibers in the dermis and is the reason skin edges retract when incised
What influences skin tension lines
Skin is anisotropic (lack similar properties in all directions) and is influenced by muscle contraction, movement of joints and other external forces
list some of the particulars when suturing tissue
Tissue strength and not suture size or number are more important determinants for dehiscence
Suture should be placed as close together as necessary
More sutures are required in thin skin
Wounds under tension increasing suture number is preferable to increasing size
Describe the corner suture
Begins like a routine horizontal mattress but instead of penetrating full thickness, only a partial thickness bite is taken, then is passed horizontally through the dermis at the point of the V and is completed as it was started
Is also called three-point or half-buried mattress suture
Is used to secure the sharp intersecting point of a Y-shaped incision
Describe the particulars of tension-relieving patterns
If the force required on individual sutures to appose skin edges increases to the point where vascular supply is compromised tension sutures can be used
Used either alone or in combination with appositional patterns
Explain the reason why sutures should be placed at least 0.5 cm from skin edges
Collangenolytic and inflammatory processes that take place during early wound healing weaken the suture-holding ability of the skin
Discuss undermining skin
Simplest tension-relieving procedure, blunt dissection has the advantage of minimizing damage to the cutaneous blood supply over sharp dissection
Depth at witch skin is undermined depends on vascular supply
In a fresh wound a distance equal to the width of the defect should be elevated on each side of the wound and can be extended half as much again if needed
Discuss tension-release incisions
Are longitudinal incisions made adjacent to the wound margin which aids in advancing skin to cover the wound
When the tissue between the wound edge and incision is undermined the elevated skin acts as a bipedicle advancement flap
Can be made on either side of the incision or both sides, when making a single release incision it should be placed at a distance approximately the width of the wound away from the wound edge
When creating two release incisions the resultant size of each new wound is approximately half of the original wound area and is preferred over one release incision
Discuss mesh expansion
Simple technique that when combined with undermining can increase the amount of skin available for mobilization
Small incisions made in staggered rows parallel to wound edge made approximately 1 cm between individual stab incisions and adjacent rows
Explain V-to-Y and Y-to V plasty
V-to-Y requires a V-shaped incision with the point of the V directed away from the defect to be closed, closure of the V incision is done by converting it to a Y
Discuss Z-Plasty
Used to relieve tension from a linear scar, change orientation of an incision line or scar or to relieve tension when closing a large defect by recruiting loose tissue from the sides of the surgical site
Represent a modification of a transposition flap
Result in a change in orientation of the central limb of the Z and a gain in length
Z is symmetric with the 3 limbs of equal length and the same angle between the two arms and the central limb
An angle of 60° is most frequently used which result in 75% gain in length
Most common complication is ischemia and necrosis of the tips of the triangular flaps
Explain W-Plasty
Designed to improve the cosmetic appearance of a scar
Scar is excised by making a series of opposing zigzag incisions in such a way that when sutured the incision will interdigitate
Discuss presuturing
Is based on the principle that skin stretch when is held in tension
It relies on the physiologic response of mechanical creep which result in skin expansion and can be achieved when sutures are placed several hours prior to removal of a skin lesion
Discuss Elastomers
Consist of a silicon pouch that can be gradually inflated percutaneously with sterile saline
Take advantage of both mechanical and biological creep and can expand the area of the skin 2-3 fold, epidermis respond to gradual inflation by an increase in mitotic activity and a net increase in epidermal tissue
Complications include pain, pressure necrosis, implant failure, wound dehiscence, and premature exposure of the expander
Describe closure of fusiform excisions
Can be used for elective scar revision with the long axis of the defect being oriented parallel to the lines of skin tension
A 3:1 or 4:1 length to width ratio will allow closure of the defect with fairly even distribution
Describe closure of circular defects
Commonly result in the formation of dog ear
Can be converted to an X or a Y-shape by tightening sutures placed at 3 or four points equidistant to each other around of the circumference of the defect
Excision of two triangles on opposite sides of the circle therefore creating a fusiform defect
The height of each triangle should be at least equal to the diameter of the circle resulting in removal of skin equivalent to 1.5 times the area of the original defect
Double S-shaped incision with a bi-winged excision, bow tie and combined V-incision are alternative methods
Describe skin flaps
Skin flaps or pedicle graft is a portion (flap) of skin that when created, can be moved from its original location to a second location on the body while by virtue of its attachment (pedicle) it maintains vascular supply
Describe the classification of skin flaps
Local or distant depending on the relationship of the donor site to recipient site
Local flaps include rotation flaps, transposition flaps and interpolating flaps
Also categorized as random or axial pattern flaps according to the nature of their vascular supply
Random pattern flaps do not have defined vascular pattern depend on the subdermal plexus for survival
Axial pattern flaps contain at least one major direct efferent and efferent cutaneous vessel
Discuss the length to width ratio
Random patter flaps length to width ratios from 1:1 to 3:1 for single pedicle and 1.5:1 to 3:1 for bipedicle
Describe the delay phenomenon
Used to enhance the blood supply to the skin to increase the chances of survival
Two stage technique involves incising and undermining the skin and subcutaneous tissue of the proposed flap and leaving it sutured in its original location for a period of time
Describe advancement flaps
Are random pattern flaps that can be either the single or bipedicle type a V-Y plasty is an example
Simple bipedicle flaps are performed either by making a single longitudinal incision on one side of the wound or by incision on each side of the defect
Discuss rotating flaps
3 types are described rotation, transposition, interpolating
Rotation flap involves creating a semicircular incision and moving the tissue laterally
A rectangular single pedicle flap that is created adjacent to the defect and subsequently rotated on its pedicle is called transposition
Moving a similar rectangular flap onto an immediately adjacent defect creates an interpolating flap
Most common indications for applying skin grafts
Large wounds that cannot heal by any other means
Discuss the classification of free grafts
Can be classified by their source in autograft (isograft), allograft (homograft) and xenograft (heterograft)
By their thickness in full-thickness composed of epidermis and entire dermis, split-thickness composed of epidermis and only a portion of the dermis
Full or split thickness free skin grafts can be applied as a solid or meshed sheets or they can be embedded in granulation tissue as pinch, punch, or tunnel grafts
Factor that would influence graft acceptance
Percentage of dermis within the graft
The thickness of dermis within the graft is directly proportional to the graft’s durability and cosmesis but inversely proportional to the graft’s ability to survive
Describe how a graft adhere to recipient site
Adhere by fibrin which binds to collagen within the graft
Vessels and fibroblast invade the fibrin matrix by day 4-5
Graft becomes firmly adhere around day 10
Describe neovascularization of a graft
New capillaries from the recipient bed invade preexisting vessels within the graft, and others cut new vascular channels into the dermis
Explain vascular bridging
Phenomenon that may enable a portion of the graft overlying relatively avascular portion of the wound to revascularize
Capillaries enter the portion of the graft overlying the avascular portion of the wound from the relative highly vascular aspect of the surrounding recipient bed to create vascular bridges across the avascular portion of the wound
Full thickness grafts bridge better because collateral circulation within the dermis of a full thickness graft is less interrupted
Describe graft contraction
After harvested grafts immediately shrink because of recoil of elastic fibers within the deep dermal layers known as primary contraction with a greater effect in full thickness grafts
Grafts composed solely of epidermis do not shrink at all
Skin graft inhibit wound contraction by accelerating the life cycle of the myofibroblast within the wound
Total percentage of dermis grafted is more important than the absolute thickness of the skin graft in preventing wound contraction
reason for a graft failure
Fluid accumulation beneath the graft, movement, and infection
Most frequently because of infection
Discuss graft failure by infection
Survival of the skin graft is better correlated to the concentration of bacteria in the recipient bed than to any other single factor, more than 105 bacteria per gram of tissue the wound should not be grafted
Type of bacteria seems to be as significant if not more as the concentration of bacteria
Concentration of some bacteria most notably β-hemolytic streptococci and pseudomonas spp require less than 105 per gram of tissue
β-hemolytic streptococci produce proteolytic enzymes, including streptokinase and staphylokinase that are destructive to both the graft and its recipient, destabilizing the fibrin network between the graft and recipient bed by catalyzing the conversion of plasminogen to plasmin which digest fibrin
Pseudomonas produce elastase which specifically degrades elastin in the dermis of the graft to which fibrin attaches
Describe the preparation of full thickness sheet grafting
Suitable sites include cranial pectoral region where the skin is relatively mobile
Graft should be cut slightly larger than the recipient bed
Subcutaneous tissue should be removed to expose the dermis and its vasculature
Fascia and fat should be sharply dissected
Should be attached to the recipient site with slight tension to keep the small dermal vessels open for inosculation
Provide the best cosmetic appearance but are not as readily accepted as split thickness grafts
Usually reserved for fresh uncontaminated wounds
Discuss split-thickness sheet grafting
Composed of epidermis and portion of the dermis and thickness is determined by the relative amount rather than the absolute amount of dermis included in the graft
Harvested by free hand knife, drum dermatome or power driven dermatome
Discuss split-thickness graft harvesting
Watson grafting knife harvest a graft 100 mm (4 inches) wide
Drum dermatome allows harvesting a graft of the exact dimension to fit the wound
Power-driven dermatomes provide precision harvesting, the widest graft is only 76 mm (3 inches)
Explain meshing sheet graft
Split or full thickness sheet graft can be applied to a recipient bed as solid or as meshed sheet, primary reason for meshing is to allow the graft to uniformly cover a wound larger than the graft itself, also to prevent blood or exudate from mechanically disrupting a newly applied graft from it delicate fibrinous and vascular attachments
Fenestrations in the graft fill with fibrin increasing graft stability
Explain some considerations of expanded meshed graft
Each portion of the wound exposed within the fenestrations must heal by contraction and epithelization
The epithelium that eventually covers the expanded fenestrations has no adnexa, causing the wound to heal with abundant diamond-shaped epithelial scar
Size of epithelial scar can be reduced by attaching the graft to the wound so that the fenestrations within the graft are parallel with the skin lines
Discuss graft acceptance and cosmesis
Thickness of the graft greatly influences its acceptance, the thinner the graft the less its metabolic needs and less its vascularity demands conversely the thinner the graft the poorer its durability and cosmetic appearance
Describe island grafts
Small pieces of full thickness or split thickness skin placed either into or onto a granulating wound, the purpose of island grafts is to increase the area of epidermis from which epithelization can proceed
Island grafts heal primarily by epithelization
Types include pinch, punch, and tunnel grafts
Describe punch grafts
Small full thickness plugs of skin that are harvested and implanted into granulation tissue using skin biopsy punches
Common donor sites are the ventrolateral aspect of the abdomen, perineum and portion of the neck that lies beneath the mane
Should be harvested in a symmetrical pattern about 1 cm apart
Subcutaneous fascia and fat should be sharply excised
Recipient holes in the granulation tissue should be created before the graft are harvested to allow hemostasis, the depth of the recipient holes should correspond to the thickness of the graft and should be placed about 6 mm apart in a symmetrical pattern
Holes should be slightly smaller to allow contraction of the graft
Usually reserved for small wounds where cosmesis is not important
Survival of 60% to 75%
Describe pinch grafts
Small disc of skin harvested by excising an elevated cone of skin that laid onto or implanted into granulation tissue sometimes referred as Reverdin grafts
A disc of optimal size is approximately 3 mm in diameter which approaches full thickness toward the center but its thickness diminishes toward the periphery
A cone of skin is elevated and excised
To implant a No 15 scalpel blade is stabbed into the granulation tissue at an acute angle to create a shallow pocket into which the graft is inserted about 3-5 mm apart epidermal side up proximal to the pocket
50% to 75% survival
Discuss tunnel grafts
Strips of split-thickness or full thickness skin implanted into tunnels created in granulation tissue
The graft are exposed days later when the have revascularize by excising the overlying granulation tissue
To implant, a long thin rat-tooth alligator forceps is inserted into the granulation tissue and advance at a depth of 5-6 mm until emerges on the opposite side to grab and pull the strip of skin through
Graft should be embedded at a right angles to the convex surface of the wound to aid entry and exit of the forceps, strips should be embedded 2 cm apart
6-10 days the roof of each tunnel is removed
60%-80% survival
Discuss graft storage
McCoy’s 5A medium is a tissue culture medium composed of balanced electrolyte solution to which amino acids, vitamins, dextrose, and pH indicator (phenol red) have been added
Split thickness king graft refrigerated at 40 C in McCoy’s 5A medium and horse serum can be successfully stored for 3 weeks
Concentration of serum in the storage medium should be 10%-33%
A color change in the McCoy’s 5A medium from cherry-red to orange-yellow indicates excessive accumulation of catabolites and need immediate application of the graft or replacement of the medium
- Describe the layers of the epidermis
Composed of 4 layers- stratum Basale, S. spinosum, S. Granulosum, S. corneum
Stratum corneum slows water loss and functions as a barrier to harmful substances
Describe debridement
Effective way to reduce bacterial load within the wound and minimize necrotic tissue
Debridement is used to alter the wound classification from infected to contaminated to clean to clean contaminated to clean
Most common types include sharp, mechanical, chemical, biological, and autolytic
Sharp and autolytic should be primarily use in equine wound care
Discuss wet-to-wet and wet-to-dry dressings
Wet-to-wet are intended to stay wet and may have to be remoistened up to six times a day much more effective at removing necrotic tissue than using gauze while causing less damage to the fibroblast and epithelial cells
Wet-to-dry performed by moistening the primary dressing (dressing against the wound bed) while leave the rest of the dressing dry, primary dressing should never be allowed to dry as this reduces effectiveness of autolytic debridement
- Discuss chemical and enzyme debridement
Chemical debridement has been used in many different forms in wound care and example includes Dakin’s solution (diluted bleach), hydrogen peroxide, acetic acid, and hypertonic saline
This debridement is nonselective and should be reserved for very contaminated wounds
Enzymatic debridement involves placing enzymes directly onto the wound bed
Most commonly used enzymes are streptokinase/streptodornase, collagenase, DNase/fibrinolysin, papain/urea, and trypsin
Enzymatic debridement is limited when large amount of necrotic tissue have to be removed and should be used after an initial sharp debridement
List the options for wound closure
Primary closure, delayed primary closure, and second intention healing
List the stages of wound healing
Inflammatory/cellular reaction stage
Debridement stage
Tissue formation/proliferation stage
Maturation/remodeling stage
Describe wound classification
Classified on the basis of degree of contamination
Clean wounds, clean contaminated, contaminated, infected
Color evaluation RYB color code
R= fresh or red and indicates granulation tissue
Y=yellow and indicates purulent debris
B=black and indicate necrotic tissue
P and G sometimes are added and indicate epithelialization and gangrenous tissue
Describe delayed primary closure
Wound is initially treated openly to allow debridement and reduce bacterial contamination followed by primary closure
Reserved for wounds that have mild to moderate bacterial contamination, minimal tissue loss, and minimal tension
Very useful in the management of abdominal incisions
Wounds should be debrided and cleaned to reduce bacterial burden
Describe hypertonic saline dressing
Curasalt, 20% hypertonic saline on kerlix gauze for the use on necrotic or heavily exudating wounds
Works by osmotic action to remove necrotic tissue and bacteria
Nonselective chemical debridement, dressing should be changed every 24-48 hours at the beginning of the treatment
Discuss growth factors
Benefit of platelet-derived growth factor (PDGF) decreases wound healing time
Acts a chemotactic agent and mitogen for fibroblasts, smooth muscle cells and inflammatory cells
Transforming growth factor-β (TGF-β) has a profibrotic function in wound healing in that it seems to encourage formation of granulation tissue
Discuss negative pressure wound therapy
Beneficial in both acute and chronic wounds
Possible benefit include increased blood flow, increased angiogenesis, increased rate of granulation tissue formation increased flap survival and decreased bacterial number and edema formation
Describe the ways to address possible pneumothorax
Placement of a chest tube
Teat cannula can be attached to a 60 ml syringe with a three-way stopcock to remove air from the chest cavity, cannula should be placed in the upper third of the chest to enable removal of the large volume of air
Discuss wounds to the abdominal cavity
Diagnostic challenge due to the numerous layers that vary depending on the location
Aseptic technique should always be used
All tissue planes should be examined
Abdominocentesis may help but in many cases the TP and cell count are within normal limits
If the peritoneal cavity has been entered abdominal exploratory is granted
Discuss axillary lacerations
Often present subcutaneous emphysema that is created when the horse moves its leg forward opening the wound and filling it with air, in some cases a pneumomediatinum occurs which can lead to pneumothorax
Describe the differences between a sinus tract and a fistula
Fistula is an abnormal passage or communication, usually between two internal organs or leading from an organ to the surface of the body
Sinus tract is defined as a cavity or channel it may be normal or pathologic
Discuss sinus tract exploration
Exploration is carried out with a malleable probe and groove director
Infusion of a vital dye such Evan’s blue further facilitates recognition of the tract during surgery
After foreign body removal all linings of the sinus tract should be curetted so that most of the bacterial contamination is removed
Tract should be flushed with sterile saline
Usually better to simply debride the cloaca rather than to close it
Discuss special considerations for chronic sinus tract
Location may indicate that the tract did not develop secondary to a foreign body
Sinus tract in the head a dental problem should be suspected
Near the base of the ear is usually the result of a choanal cyst (ear tooth)
Over the pole or withers region may indicate a development of an infected bursa in this area called pole evil and fistulous withers (Brucella)
Discuss sarcoids
Most common tumor in the horse, is a cutaneous fibroblastic neoplasia with proliferative epithelial component
Classified histopathologically as benign tumors because of the morphologic characteristics of the fibroblasts and because many sarcoids are slow growing and cause little if any physical problem (misleading)
sarcoid subtypes based on clinical appearance
Occult
Verrucous
Nodular fibroblastic
Ulcerative fibroblastic
Mixed tumors
Malevolent (most aggressive)
etiology of sarcoids
QH and related stock breeds are twice as likely to develop sarcoids and TBH
Direct genetic linkage has been reported between equine leukocyte antigen (ELA) and risk for equine sarcoid
ELA alleles A3 and W13 were strongly associated with risk for sarcoids in TBH and Swiss French and Irish warmblood
The genetic predisposition for and age of onset of sarcoids suggest that both genetic and exogenous factors may play a role in development
Presence of bovine papilloma virus (BPV) DNA in nearly all equine sarcoid tissues examined
sarcoid treatment
Sarcoids can transform to a more aggressive phenotype after incomplete or unsuccessful treatment and are the harder to resolve
Options include surgical excision (15.8%-82%0, laser ablation (38%), cryotherapy (91%), hyperthermia, radiotherapy, immunotherapy (0%-40%), intralesional cisplatin,
Discuss squamous cell carcinoma
Malignant locally invasive neoplasia of squamous epithelial cells
Second most common tumor in horses
Sites of predilection include areas lacking pigmentation, poorly haired regions and skin near mucucutaneous junctions
Should be considered in horses with chronic refractory hoof abscess
SCC typically spreads to surrounding tissues and local lymph nodes
treatment for SCC
Surgical excision, radiation, topical application of antimitotic, intralesional chemotherapy, cryotherapy, laser excision, hyperthermia, immunotherapy, and photodynamic therapy
Discuss irradiation treatment for SCC
External beam radiotherapy, implanted radiation devices, and b-emitting wands
Strontium wands (b-radiation) can be used to treat small superficial plaques on the cornea sclera or conjunctiva
Describe melanomas
Melanomas account for 4%-15% of all skin tumors
Majority occur in gray horses
Progression from melanocyte accumulation to melanoma formation has been documented in melanoma prone locations
types of melanomas
Melanocytic nevi composed of larger pleomorphic melanocytes with an increased number of mitotic figures, binucleate cells and variable cytoplasmic pigmentation
Dermal melanomas appear benign on histopathology and are composed of smaller homogenous dendritic cells with condensed chromatin, dense pigmentation and no visible mitosis
Dermal melanomatosis same as dermal melanomas
Malignant melanomas rare and are classified on the basis of the presence of both histopathologic and clinical characteristics of malignancy and frequently invasive and associated with poor prognosis for complete resolution
treatment for melanomas
Dermal melanomas and melanocytic nevi have similar characteristics and surgical excision is curative in the majority of cases
Complete excision is difficult with large lesions such as dermal melanomatosis but surgical debulking can be palliative
Oral cimetidine has been recommended because its antitumor activity and is a histamine receptor agonist, immunomodulation of lymphocyte activity via histamine receptor interaction is postulated as a mechanism of antitumor activity 2.5 mg/kg Q-8
Additional treatment include intralesional chemotherapy and cryotherapy
Discuss mast cell tumors
Equine cutaneous mastocytosis (ECM) less common in horses
Benign solitary nodular cutaneous form is the most common, although malignant ECM and congenital disseminated form have been recognized
Release of inflammatory products from accumulated eosinophils and mast cells result in necrosis and later granulomatous reaction develops with fibrosis and subsequent encapsulation of the nodule
Discuss cutaneous habronemiasis
Proliferative ulcerative lesion produced by aberrant migration of larvae of three endoparasites (Habronema muscae, Habronema microstoma, and Draschia megastoma)
Cutaneous form all called summer sores develop when larvae are attached to wound beds or aberrant moist surfaces, including the penis, prepuce, and ocular adnexa
Histopathologic examination is recommended because habronemiasis can develop secondary to an underlying neoplastic of infectious condition
habronemiasis treatment
Treatment is aimed at reducing the size of the lesions resolving the inflammatory or allergic component and preventing reinfestation
Topical preparation that combine organophosphates, corticosteroids, DMSO and nitrofurazone have been used
Discuss pythiosis
Cutaneous disease caused by invasion of the organism Pythium insidiosum a fungus-like oomycete, occurs principally in warm tropical regions
Infection happens by invasion through small wounds or skin breaks typically in lakes swamps or flooded lands
Pruritic; sinus tracts are visible and often contain gritty coral like masses called kunker or leeches
Pythiosis occur most often in the distal extremities and ventral body wall
treatment for pythiosis
Surgical excision is the treatment of choice
Systemic, topical and intralesional antifungals have been used but recurrence is common
Discuss papillomatosis
Papillomaviruses are Very host- and tissue-specific and are the causative agents of most warts seen in mammals
Equine papillomatosis and aural plaques are caused by equine papillomaviruses (EqPV)
Infect the basal layer of the epidermis resulting in an abnormal proliferation and hyperkeratosis of the epithelium
Discuss dentigerous cyst
Congenital defect, it arises as a result of incomplete closure of the first brachial cleft during embryologic development
Contain dental elements, such as enamel dentin and cementum
The epidermal lining differentiates as does normal epidermis and the cyst becomes nodular as it begins to fill with keratin
Typically, unilateral swelling at the base of the ear but can occur in other locations on the head and sinus
treatment for dentigerous cyst
If desire surgical excision with complete extirpation of the cyst lining is necessary to prevent recurrence
The plane of dissection should be closed to the wall of the cyst as possible to prevent damage to the auriculopalpebral nerve and auricular muscles as well as to minimize hemorrhage
