Physiology of wound healing Flashcards
Name the layers of the epidermis from most superficial to most deep
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum Spinosum
- Stratum basale
5 layers; Attached to dermis by basement membrane; Avascular; Ridge and groove interdigitation to prevent shearing
Epidermis
½ mm thick
What is the turnover time for epidermal regeneration?
Age 18-25 years = 14-21 days
Age 35 years = 42 days
What are the 4 big epidermal cell types?
- Keratinocytes - makes up 90% of cells - produces keratin
- Melanocytes - produces melanin
- Merkel cells - mechano receptors
- Langerhans cells - fight infection in epidermis
What are the functions of the epidermis?
- Provides a physical and chemical barrier
- Regulates fluid
- Provides light touch sensation
- assists with thermoregulation
- Assists with excretion
- Critical to endogenous vit D production
- contributes to cosmoses/ appearance
2 layers; Highly vascular; Strong and elastic due to collagen and elastin; Network of lymphatics, capillaries, and cutaneous nerve ending
Dermis
2-4 mm thick
- beefy, bright red when healthy
What are the two layers of the dermis?
- papillary - more superficial, fairy thin; loosely woven fibers
- reticular - deeper, thicker
What are the cell types found in the dermis?
- Fibroblasts - produce collagen and elastin; provides flexibility
- Macrophages/ WBCs
- Mast cells - chemical mediators (histamine); causes vasodilation
What layers do blisters form between?
between the bottom layer of the epidermis and top layer of dermis
What are the functions of the dermis?
- Supports and nourishes epidermis
- Houses epidermal appendages
- Assists with infection control
- Assists with thermoregulation
- Provides sensation
What is the function of adipose tissue ?
- Energy
- Cushion (protects underlying tissues)
- Insulation
- Stores fat-soluble vitamins
What are different types of subcutaneous tissue?
- Adipose - white/ pale yellow appearance when healthy
- Fascia - thin, transparent
- Muscles - dark red
- Tendons - cream
- Ligaments - white in comparison to tendons
- Joint capsules - cream
- Bone - white
Fibrous connective tissue; Separates and surrounds structures; Facilitates movement
Fascia
What tissues are involved in superficial thickness wound?
epidermis
- abrasion, superficial (1st degree) burn, stage 1 pressure ulcer
- skin is red
What tissues are involved in partial thickness wound?
epidermis and dermis
- Superficial partial thickness and deep partial thickness (2nd degree) burn; Stage 2 pressure ulcer; Wagner (diabetic) grade 1 ulcer
What tissues are involved in full thickness wound?
Epidermis, Dermis, Subcutaneous tissue, and May extend into deeper tissue
- Full thickness (3rd degree) burn, Subdermal (4th degree) burn, Stage 3 and 4 pressure ulcer, Wagner (diabetic) grade 2-5 ulcer
What are the phases of normal wound healing
- inflammation (4-6 days)
- proliferation (4-24 days)
- maturation and remodeling (21 days - 2 years)
Essential to healing process; Controlling bleeding and combating infection; Signaling cells necessary for repair and regeneration; Vascular and cellular response; Acute usually lasts 24-48 hours then subacute up to 6 days
Inflammatory phase
What are the cardinal signs of the inflammatory phase?
- Swelling
- Redness
- Warmth
- Pain
- Decreased function
Type of response that occurs during inflammation:
- Transudate produces localized edema
- Blood vessels constrict to reduce blood loss
- Platelets cluster together
- Platelets release chemical mediators
- Vasodilation: Exudate formation, Histamine release, Prostaglandin release
Vascular response
What is the cellular response during inflammation?
- Platelets - initiate wound healing, released from damaged vessels
- PMNs - 1st cell to site of injury, cleans the wound
- Fibroblasts
- Macrophages
- Mast cells
Rebuilds the damaged structures and provides strength to the wound
- Four Events: Angiogenesis, Granulation tissue formation (lattice work), Epithelialization (new skin buds on ladder), and Wound contraction
- Resurfacing of wound bed
- Red, Beefy, Fragile
Proliferative phase
Modifies the immature new tissue to mature tissue; Epithelial tissue must be strengthened and reorganized to fit surrounding tissue; Changes in the form, bulk, and strength of epithelial tissue ; New collagen synthesis, Old collagen is broken down, Reorientation of collagen fibers, Induction and Tension Theory
Maturation/ remodeling phase
What are the two ways soft tissue can heal?
- Regeneration of new epithelial tissue
- Thicker fibrous scar tissue
- Epidermis = regenerates
- Dermis = usually regenerates
- Subcutaneous/Deeper Tissues = scar formation
What are the factors that affect wound healing?
- Wound characteristics
- Local factors
- Systemic factors
What wound are wound characteristics that affect wound healing?
- Mechanism of onset
- Time since onset
- Wound location
- Wound dimensions
- Temperature
- Wound hydration
- Necrotic tissue or foreign bodies
- Infection
What timeframe denotes acute vs chronic wounds
Acute < 30days
Chronic >30 days
extreme dryness
desiccation
result of too much moisture in wound; skin softens and turns white due to consistently being wet
maceration
Overproduction of immature collagen, red, raised, fibrous lesion, stays within edges of wound
hypertrophic scar
Tissue extends beyond edges of original wound
keloid scar
loss of superficial skin layer
denuded
- caused by exposure to urine, feces, wound drainage
generalized redness
errythemia
linear crack in skin extending into dermis or deeper
fissure
clear, water drainage that is usually seen first
transudate
yellowy, viscous drainage; more protein, seen further in healing stages
exudate
