Wound Healing Flashcards
Granulation Tissue
Initial phase of repair; consists of fibroblasts secreting Type III collagen, capillaries, and myofibroblasts.
Characterized by:
- acute inflammation
- neovascularization
- edema
Causes of delayed wound healing
Infection, Vitamin C, Copper, or Zinc deficiency, or other causes such as foreign body, ischemia, diabetes, or malnutrition
Secondary Intention
Edges of wound are not brought together. Granulation tissue fills the defect, myofibroblasts then contract and form a scar
Fibrosis
Excessive deposition of collagen in tissue. Often triggered by macrophages and chronic inflammation
When does repair occur
When regenerative cells are lost (i.e. deep skin cut) or when a tissue lacks regenerative capacity
stem cell location in skin
basal layer
Keloid
excess production of scar tissue that is OUT OF PROPORTION to wound; characterized by Type III Collagen. Affects African Americans in earlobes, face, and upper extremities
Steps of Repair by Connective tissue
- Inflammation
- Angiogenesis
- Migration and proliferation of fibroblasts
- Scar formation
- Connective tissue remodeling
Hypertrophic scar
excess production of scar tissue that is localized to wound
Permanent tissues
Lack regenerative potential. Healing must occur through fibrosis. Examples include myocardium, skeletal muscle, and neurons.
Labile Tissue
Possess stem cells that continuously cycle and regenerate the tissue. Examples include small and large bowel, skin, and bone marrow
Collagenase
Removes Type III collagen in granulation tissue and replaces it with Type I collagen; Requires Zinc cofactor!
TGF-beta
important fibroblast growth factor; also inhibits inflammation
stem cells in bone marrow and marker
hematopoietic stem cells; CD 34
Platelet-derived Growth Factor
growth factor for endothelium, smooth muscle, and fibroblasts
Steps of Cutaneous Wound Healing
- Inflammation (injury and formation of clot)
- Proliferation (granulation, re-epithelialization of wound surface)
- Maturation (ECM deposition, tissue remodeling)
Zinc
Cofactor for collagenase
Define Regeneration
replacement of damaged tissue with native tissue
Vascular endothelial growth factor (VEGF)
important for angiogenesis
Stem cell location in small and large bowel
mucosal crypts
Stable Tissue
Cells are normally quiescent, but can reenter cell cycle and regenerate when necessary. Examples include liver cells.
Define Repair
replacement of damaged tissue with a fibrous scar
Type III collagen
pliable material that is present in granulation tissue, embryonic tissue, uterus, and keloids
Tensile strength of scar
about 70-80% of strength of origninal tissue
Scar
Pale, avascular, nearly acellular collagenous tissue with a few fibroblasts. Surface is covered by intact epithelium
TGF-alpha
epithelial and fibroblast growth factor
Vitamin C
Cofactor in hydroxylation of proline and lysine in procollagen residues; important for collagen formation
3 types of tissue based on regenerative capacity
Labile, Stable, and Permanent
Dehiscence
rupture of a wound; most commonly seen after abdominal surgery
Copper
Cofactor for lysyl oxydase, which cross-links lysine and hydroxylysine to form stable collagen polymers
Fibroblast growth factor
important for angiogenesis
Primary Intention
Would edges are brought together (as in suturing); leads to minimal scar formation
