healing stages

healing by first intention (primary union)

wound edges are clean, uninfected & brought closely together by surgical sutures/glue; minimal tissue loss, little granulation loss, minima, scarring

hemostasis & inflammation

blood clot forms quickly, neutrophils/macrophages clear debris within first few days; FIRST PHASE OF PRIMARY UNION

proliferation

epithelial cells migrate across incision gap beneath scab within 24-48hrs; fibroblasts lay down collagen to bridge edges; SECOND PHASE OF PRIMARY UNION

remodeling

tensile strength increases gradually as type III collagen is replaced by stronger type I collagen over weeks/months; LAST PHASE OF PRIMARY UNION

healing by second intention (secondary union)

significant tissue loss, gaping wound edges that cannot be easily approximated, wound is heavily infected and must be left open to heal bottom up; extensive granulation tissue required to fill gap, wound contractions via myoblasts, results in larger/more noticeable scar

granulation tissue

highly vascular, pinkish-red tissue rich in new capillaries & fibroblasts to fill the wound bed; FIRST PHASE OF SECONDARY UNION

contraction

myofibroblasts pull margins of wound inward, drastically shrinking overall surface area of defect; SECOND PHASE OF SECONDARY UNION

epithelialization

epithelial cells migrate inward only from the healthy edges of wound; LAST PHASE OF SECONDARY UNION

healing by third intention (tertiary closure/delayed primary closure)

hybrid approach where wound is left open for a few days to allow infection, edema, contamination to resolve then surgically closed; control environment to prevent trapping bacteria in a closed space

initial management

wound is debrided, packed, or left open allowing initial granulation tissue to begin forming and infection to clear (3-5 days); FIRST PHASE OF TERTIARY INTENTION

delayed closure

once wound bed is clean/safe, edges are brought together surgically to heal like a primary-intention wound resulting in intermediate level scarring; LAST PHASE IN TERTIARY INTENTION