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
