Study Set Content:
has profound effects on repair; protein deficiency and vitamin C deficiency inhibit collagen synthesis and retard healing
Nutritional Status
have well-documented anti-inflammatory effects, and their administration may result in
weakness of the scar due to inhibition of TGF-β production and diminished fibrosis
Glucocorticoids (steroids)
may cause wounds to pull apart, or dehisce.
Mechanical factors such as increased local pressure
due to peripheral vascular disease, arteriosclerosis, and diabetes or due to obstructed venous drainage (e.g., in varicose veins), also impairs healing
Poor Perfusion
impede healing by perpetuating chronic inflammation.
Foreign bodies such as fragments of steel, glass, or
even bone
Complete restoration can occur only in tissues composed of stable and labile cells
The type and extent of tissue injury
When the injury involves only the epithelial layer, the principal mechanism of repair is called
Epithelial regeneration or primary union or healing by first intention
Healing by First Intention
- formation of a blood clot
- Within 24 hours, neutrophils are seen
- Within 24 to 48 hours - thin but continuous epithelial layer that closes the wound
- By day 3, neutrophils have been largely replaced by macrophages, and granulation tissue
- By day 5, neovascularization reaches its peak
- During the second week, there is continued collagen accumulation and fibroblast proliferation
- By the end of the first month, the scar comprises a cellular connective tissue largely devoid of inflammatory cells and covered by an essentially normal epidermis
Healing by Second Intention
- fibrin clot is larger, and there is more exudate and necrotic debris in the wounded area
- Much larger amounts of granulation tissue are formed to fill a bigger gap caused by the larger area of deficit
- At first a provisional matrix containing fibrin, plasma fibronectin, and type III collagen is formed then replaced by type I collagen
- Wound contraction helps to close the wound by decreasing the gap between its dermal edges and by reducing the wound surface area.
- Within 6 weeks, large skin defects may be reduced to 5% to 10% of their original size
Carefully sutured wounds have approximately
70% of the strength of the normal skin
The recovery of tensile strength results from the excess of collagen synthesis over collagen degradation during the first 2 months of healing by
Cross-linking of collagen and increased fiber size
Wound strength reaches approximately ____ to ____ of normal by 3 months
70% - 80%
used to denote the excessive deposition of collagen and other ECM components in a tissue
fibrosis
Fibrotic disorders include diverse chronic and debilitating diseases such as
Live cirrhosis, systemic sclerosis (scleroderma), fibrosing diseases of the lung (idiopathic pulmonary fibrosis, pneumoconioses, and drug- and radiation-induced pulmonary fibrosis)
develop most often in elderly people as a result of chronic venous hypertension, which may be caused by severe varicose veins or congestive heart failure.
Venous Leg Ulcers
Deposits of iron pigment (hemosiderin) are common, resulting from red cell breakdown, and there may be accompanying chronic inflammation.
Venous Leg Ulcers
develop in individuals with atherosclerosis of peripheral arteries, especially associated
with diabetes
Arterial Ulcers
affect the lower extremities, particularly the feet; There is tissue necrosis and failure to heal as a result of vascular disease causing ischemia, neuropathy, systemic metabolic abnormalities, and secondary infections.
Diabetic Ulcers
are areas of skin ulceration and necrosis of underlying tissues caused by prolonged compression of tissues against a bone; The lesions are caused by mechanical pressure
and local ischemia
Pressure Sores
Excessive formation of the components of the repair process can give rise to
Hypertrophic scars and keloids
