Early stages of skin wound healing and granulation tissue
THE CONTEXT
Skin wounds progress through hemostasis, inflammation, and cell proliferation before remodeling produces a fibrous scar.
Hemostasis and inflammation
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Within minutes of traumatic injury, a platelet-containing hemostatic plug stops bleeding and provides a scaffold for inflammatory cell infiltration and formation of a stable clot.
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Over the next 6–48 hours, neutrophils followed by monocytes are recruited to eliminate offending agents and clear debris.
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Macrophages are central to repair: different populations clear microbes and necrotic tissue, promote inflammation, and produce growth factors that stimulate subsequent cell proliferation.
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Inflammation resolves as injurious agents and necrotic cells are cleared.
Cell proliferation and wound closure
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The next stage takes up to 10 days and involves proliferation and migration of epithelial cells, endothelial and other vascular cells, and fibroblasts.
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Epithelial cells respond to local growth factors and migrate to cover the wound.
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Endothelial and other vascular cells proliferate to form new blood vessels through angiogenesis.
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Fibroblasts proliferate, migrate into the injury site, and deposit collagen fibers that form the scar.
Granulation tissue and subsequent changes
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Granulation tissue consists of proliferating fibroblasts, extracellular matrix, and new blood vessels. It has a pink, soft, granular gross appearance.
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An eschar is the scab over damaged skin.
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The illustrated sequence of healing by second intention progresses from clot formation and inflammation through epithelial proliferation and granulation tissue formation to remodeling into a fibrous scar.