Wound Healing is the coordinated biological process through which damaged tissue restores structural integrity and, where possible, function. It involves overlapping phases conventionally described as haemostasis, inflammation, proliferation and remodelling, although these phases are not rigidly separated in time. Haemostasis limits bleeding through vasoconstriction, platelet activation and coagulation, while inflammatory cells remove damaged material and help coordinate repair.
The proliferative phase includes formation of granulation tissue, new blood vessels, extracellular matrix and re-epithelialisation, followed by remodelling in which collagen organisation and mechanical properties change over a prolonged period. Healing can occur by primary intention when wound edges are closely approximated, by secondary intention when a tissue defect must fill through granulation and contraction, or through more complex processes involving delayed closure.
The inflammatory stage is essential but must be appropriately regulated. Platelets release mediators that contribute to clot formation and signalling, while neutrophils and macrophages enter the injured area and participate in microbial defence and removal of damaged tissue. Macrophages have particularly important roles because they can promote transition from inflammation towards repair by producing cytokines and growth factors. Excessive, prolonged or dysregulated inflammation can delay healing and contribute to chronic wounds. Conversely, insufficient inflammatory activity can impair microbial control and clearance of damaged tissue. The balance between host defence, tissue injury and resolution therefore strongly influences whether a wound progresses normally or becomes persistently inflamed.
Proliferative Wound Healing involves several interacting cellular processes. Fibroblasts produce extracellular matrix components, including collagen, while endothelial cells participate in angiogenesis and keratinocytes migrate across the wound surface during re-epithelialisation. Granulation tissue is characterised by a vascular, cellular and extracellular-matrix-rich environment that progressively replaces the initial wound bed. Myofibroblasts can generate contractile forces that reduce wound area, particularly in wounds healing by secondary intention. Adequate oxygenation, nutrients, viable tissue and a suitable extracellular environment are necessary for these processes. The resulting tissue is not initially equivalent to uninjured tissue because the architecture, vascularity and collagen arrangement continue changing during subsequent remodelling.
Collagen metabolism is central to long-term repair. Early wound matrix contains relatively disorganised collagen and other provisional components, while later remodelling involves changes in collagen synthesis, degradation, cross-linking and fibre organisation. Matrix metalloproteinases and their inhibitors regulate extracellular matrix turnover, and imbalance can contribute to chronic wound pathology. Scar tissue generally has altered collagen architecture compared with normal skin and therefore does not fully reproduce the original tissue's mechanical and functional characteristics. Tensile strength increases progressively during healing but does not ordinarily return immediately to the strength of uninjured skin. This explains why recently healed wounds remain vulnerable to disruption even when the surface appears closed.
Wound Healing is strongly affected by local and systemic conditions. Infection increases inflammatory burden and can damage newly forming tissue, while poor perfusion restricts oxygen and nutrient delivery and impairs immune-cell function and matrix production. Diabetes can interfere through multiple mechanisms, including vascular disease, neuropathy, altered inflammatory responses and impaired cellular repair. Smoking and nicotine exposure can adversely affect oxygenation, vascular function and tissue repair. Nutritional deficiencies, advanced age, some medications, immune dysfunction, repeated mechanical trauma and excessive wound tension can also delay closure. Effective wound management therefore requires attention not only to the wound itself but also to the biological and environmental conditions that support or obstruct repair.
Clinical wound care involves assessment of wound type, depth, tissue viability, contamination, infection risk, perfusion, exudate, pain and surrounding skin. Appropriate management may include haemorrhage control, cleansing, protection, moisture-balanced dressings, debridement when indicated, infection management, pressure relief, restoration of perfusion and closure when appropriate. Modern wound care generally recognises that excessively dry or excessively wet conditions can both be problematic, making moisture balance an important consideration. Debridement removes devitalised tissue when clinically appropriate, but treatment must be individualised because viable tissue should not be unnecessarily damaged. Complex or chronic wounds may require multidisciplinary management involving surgical, vascular, diabetic, nutritional or rehabilitation expertise.
Wounds are commonly classified as acute or chronic according to their clinical course and underlying biology. Acute wounds usually progress through an orderly repair sequence, whereas chronic wounds may become trapped in persistent inflammation, impaired proliferation, abnormal matrix turnover or recurrent tissue injury. Examples of chronic wound contexts include pressure-related injury, venous disease and diabetic foot pathology. Infection can be distinguished conceptually from colonisation because microorganisms may be present without causing invasive infection, while clinical deterioration, spreading inflammation, increasing pain, purulent material or systemic illness may indicate a clinically significant infectious process. Wound assessment should consequently consider the whole clinical picture rather than relying solely on the presence of bacteria.
The outcome of Wound Healing ranges from restoration with minimal visible evidence to substantial fibrosis, contracture or chronic non-healing. Factors such as wound depth, anatomical location, mechanical forces, genetic predisposition and treatment influence the resulting scar. Excessive contraction can restrict movement across joints, while hypertrophic or keloid scarring can produce persistent cosmetic, symptomatic or functional effects. Poor healing can also result in dehiscence, fistula formation or recurrent breakdown. Understanding Wound Healing is therefore important across surgery, dermatology, emergency care, rehabilitation and chronic disease management because successful closure is only one part of recovery; the quality, strength and function of the repaired tissue also matter.
