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tissue repair

Terms in this set (11)

where does the processes of tissue repair and inflammation overlap?
-inflammatory phase:
debris, bacteria phagocytosed removed; stimulatory factors released for migration and proliferation of cells in the proliferative phase
- remodeling phase:
remodeling and realignment of collagen followed by apoptosis to remove unneeded cells
- proliferative phase:
includes angiogenesis, deposition of collagen, formation of granulation tissue, cell growth, and contraction of the wound
what is the goal of tissue repair?
- restore function
- prevent infection
- resolve the walled off entity
- replace injured cells with normally-functioning replacement cells
describe the sequence of events in the inflammatory phase of wound healing
- initiated at time of injury
- prepares wound for healing
- includes hemostasis and vascular and cellular stages of inflammation:
~ hemostasis: constriction of blood vessels, platelet activation and aggregation initiated, clotting
~ vascular phase: vessels dilate, capillary permeability increases
~cellular phase: phagocyte migration --> digestion, removal of microbes, fibrin, extracellular debris, foreign substances
- macrophages phagocytize materials, release growth factors that act on epithelial cells to stimulate growth, stimulate angiogenesis, attract fibroblasts
describe the sequence of events in the proliferative phase of wound healing
begins 2-3 days after injury, may last weeks (building new tissue)
- fibroblast and endothelial cell proliferation forms granulation tissue: new microcirculatory vessels and new connective tissue (collagen, fibronectin)
- capillary beds formed
- white cells and nutrients leak into tissues
- epithelialization occurs: migration, proliferation, differentiation of epithelial cells --> new surface layer formed at wound edges
- collagen and fibroblast accumulation continues
- by second week, leukocytes have cleared the area
- edema has diminished
- wound blanches as blood vessels generate
describe the sequences of events in the remodeling phase of wound healing
starts ~3 weeks after injury and may continue for 6 months or more
- remodeling of scar tissue
- fibroblasts synthesize collagen AND collagenase enzymes lyse collagen --> scar architecture is reoriented in order to enhance would tensile strength
what are the three cell types that may or may not undergo regeneration? why?
LABILE: divide and replicate throughout life; skin epithelial cells, oral cavity, others
FIXED/PERMANENT: cannot undergo mitotic devision; cardiac, skeletal, nerve cells
STABLE: stop dividing when growth halts; may regenerate under appropriate stimulus; kidney liver parenchyma, smooth muscle cells, vascular endothelial cells
how is the healing process regulated?
CHEMICAL MEDIATORS:
- interleukins
- interferons
- TNF-alpha
- arachidonic acid derivatives
GROWTH FACTORS
- platelet-derived
- fibroblast
- transforming
- epithelial
- connective
- vascular endothelial
what are extracellular matrix materials? what roles do they play in tissue repair?
- fibrous structural proteins: collagen, elastin fibers
- water-hydrated gels: proteoglycans, hyaluronic acid
- adhesive glycoproteins: fibronectin, laminin
compare and contrast primary and secondary intention
PRIMARY:
- if no tissue is lost
- may be achieved if an incision is closed with sutures
SECONDARY:
- may occur when closure is not possible or when the wound becomes contaminated
- tissue is lost
- heals more slowly and is accompanied by larger amounts of scar tissue
- wounds undergo "contraction": concentric reduction in size; involves movement of fibroblasts and "tightening" of myofibroblasts on skin edges
what factors affect wound healing? why?
- malnutrition: successful healing requires adequate stores of nutrients (proteins, carbohydrates, fats, vitamins)
- blood flow and oxygen delivery: sources of impaired flow, molecular oxygen, treatment, mechanism (increased partial pressure of oxygen dissolved in plasma --> increases oxygen delivery)
- impair inflammatory and immune responses (source: disorders of phagocytic function, diabetes mellitus, corticosteroid drugs)
- infection
- bite sources
- young age: neonates, children
- older age: patients 65 years old and older
describe the effects of age on wound healing.
YOUNG AGE:
- children have a greater capacity for repair but immune system immaturity and inadequate nutritional reserves may confound wound healing and treatment depends on wound and patient considerations
OLDER AGE (65 or older):
- decreased thickness of dermis
- reduced fibroblasts and collagen synthesis
- hindered wound contraction
- slower re-epithelialization of open wounds
- to mitigate/prevent: ensure older adults consume sufficient amount of zinc, protein, arginine, and vitamin C
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