Wound Healing Flashcards
The hypodermis (subcutis) lies below the dermis and is also known as the_____.
Superficial fascia
Direct cutaneous vessels run ____ to the skin, and contain perpendicular branches, that form three layers starting from bottom up:
- Parallel to the skin
- Deep/subdermal plexus
- Cutaneous/Middle of plexus
- Subpapillary/Superficial plexus
Within the subdermal plexus, list areas where the panniculus muscle is present and where it is absent.
- Panniculus present
- Trunk, neck
- Must undermine fascial plane beneath muscle
- Panniculus absent
- Extremities, part of the head
- Undermine under deep surface of the dermis
Phases of wound healing
- Inflammation
- Hemorrhage, clotting, cellular influx via growth factors and cytokines, debridement
- Repair (proliferative)
- Granulation, contraction, epithelialization
- Maturation
Neutrophils -
- When do they arive?
- Are they essential for healing?
- Their function?
- Arrive in about 6 hours
- NOT essential for healing
- Stay for 2-3 days
- Phagocytize bacteria and debris
- Proteolytic enzymes
- O2-radicles
- Monocyte stimulation
Do you need bacteria for pus formation?
No, pus is dead neutrophils, degraded tissue, and wound fluid, with or without bacteria.
Macrophages
- When do they arrive?
- Are they essential for wound healing?
- Functions?
- Arrive in about 12 hours
- ESSENTIAL for wound healing
- Drawn by endotoxins, collagen fragments
- Phagocytosis of large particles
- Produce cytokines that potentiate immune response
- Produce growth factors for cellular proliferation, INCLUDING FIBROBLASTS
- Recruit mesenchymal cells, stimulate angiogenesis, and modulate wound matrix
Lymphocytes
Arrival, function
- Arrive after neutrophils and macrophages
- Not essential for wound healing
- Modulate migration and protein syntehsis of other cells
Repair phase
When does it begin? How long does it last? Characterized by:
- Begins at days 3-5
- Lasts 2-3 weeks
- Characterized by:
- Angiogensis
- Fibroplasia
- Contraction
- Epithelialization
Granulation tissue =
Fibroblasts + new capillaries
Angiogenesis
- New capillaries form from migration and proliferation of endothelial cells
- response to growth facotrs produced by macrophages
- Regulated by proteins in extracellular matrix
Fibroplasia
- Proliferation of fibroblasts and production of collagen
- Fibroblasts migration influenced by growth factors and integrin receptors in extracellular matrix
- Collagen type III replaced by type I as fibroblasts fill the wound
- Greatest increase in collagen content occurs 7-14 days after wounding
- Then slow gian in stregnth over several months
Granulation Tissue
- Follow fibroblasts along collagen strands
- Capillary buds from existing vessel –> unite with other buds or damaged vessels
- Bring oxygen and nutrients to the wound
- Remove waste
- Appears at days 3-5 and formed at a rate of 0.4 to 1 mm/day
- Fills defect
- Barrier to infection
- Surface for epithelialization and source of myofibroblasts (reason why wound can contract)
- Should be redish/pink - like a watermelon color
Wound Contraction
- Process that decreases the size of a wound
- Migration of myofibroblasts towards center
- Centripital force on wound edges
- Ceases when surrounding skin equals contracting forces. Can stop with inadequate myofibroblasts.
- Inhibited or delayed by corticosteroids, some chemotherapy drugs, smooth muscle relaxants
Is wound contraction dependent of epithelialization?
No, wound contraction is independent of epithelialization, but often concurrent.
