{"id":6568,"date":"2026-06-03T14:23:22","date_gmt":"2026-06-03T18:23:22","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&p=6568"},"modified":"2026-06-09T15:22:58","modified_gmt":"2026-06-09T19:22:58","slug":"wound-healing","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/wound-healing\/","title":{"raw":"Section 14:\u00a0 Wound Healing","rendered":"Section 14:\u00a0 Wound Healing"},"content":{"raw":"Any break in skin in a wound.<\/strong>\u00a0 All wounds progress through four phases:\r\n\r\n\r\n\r\n\r\n\r\n\r\n
1.\u00a0 Hemostasis<\/strong><\/span><\/td>\r\nCellular damage triggers cytokine release attracting macrophages, neutrophils, platelets, and mast cells.\r\n\r\nPlatelet plug and fibrin mesh form to stop bleeding and contain the area.<\/td>\r\n<\/tr>\r\n
2.\u00a0 Inflammation<\/strong><\/span><\/td>\r\nMacrophages and neutrophils remove pathogens and debris.\r\n\r\nPro-inflammatory mediators<\/strong> (histamine, prostaglandin, bradykinin) induce vasodilation, increased capillary permeability and trigger nociceptors producing the 4 cardinal signs of inflammation (redness, warmth, swelling, and pain).<\/td>\r\n<\/tr>\r\n
3.\u00a0 Granulation and Proliferation<\/strong><\/span><\/td>\r\nActivated cells (fibroblasts, macrophages, epithelial and endothelial cells) release growth factors stimulating angiogenesis<\/strong> and formation of granulation tissue<\/strong> (pink, moist, fragile, highly vascular).\r\n\r\nFibroblasts<\/strong> produce collagen that crosslink and contracts across the wound to strengthen repair.\r\n\r\nStem cells<\/strong> undergo mitosis to replace lost cells.<\/td>\r\n<\/tr>\r\n
4.\u00a0 Remodeling<\/strong><\/span><\/td>\r\nCollagen-rich scar tissue may gradually be replaced by epithelial cells over time.\r\n\r\nExtent of remodeling depends on wound dimensions, patient age, health, and genetics.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n[caption id=\"attachment_2364\" align=\"alignnone\" width=\"300\"]\"Tissue<\/a> Tissue Healing: During wound repair, collagen fibers are laid down randomly by fibroblasts that move into repair the area.[\/caption]\r\n

Three Categories of Wound Healing<\/strong><\/span><\/h3>\r\n\r\n\r\n\r\n\r\n\r\n
Primary (1st) Intention<\/strong><\/span><\/td>\r\nMinimal-gap, uninfected wounds (e.g., clean surgical incisions).\r\n\r\nEdges approximated with sutures, staples, or adhesive closures.\r\n\r\nCriteria:\u00a0 clean, fresh (within 4-8 hours), free of debris, and necrosis.\r\n\r\nResults in minimal scarring and loss of functional tissue.<\/td>\r\n<\/tr>\r\n
Secondary (2nd) Intention<\/strong><\/span><\/td>\r\nLarger, deeper, or infected wounds where suturing is not feasible.\r\n\r\nHeals from the base outward; cleaned and dressed to prevent infection.\r\n\r\nResults in more granulation tissue, more collagen, greater scare formation and reduced functional structures (fewer hair follicles, glands, sensory nerved endings, melanocytes).<\/td>\r\n<\/tr>\r\n
Tertiary (3rd) Intention<\/strong><\/span><\/td>\r\nA wound healing by 2nd intention is purposely interrupted during granulation to close it mechanically (skin grafts, sutures, staples) after initial treatment of infection and edema.\r\n\r\nIn this type of process, debridement may also have been required prior to closing the wound mechanically.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

Burn Wounds<\/strong><\/span><\/h3>\r\n

Burns can be thermal, electrical,<\/strong> or chemical,<\/strong> affecting skin, respiratory tract (smoke inhalation), or digestive tract (chemical ingestion).\u00a0 Severity depends on cause, temperature\/strength\/concentration, duration, body area, and site.\u00a0 Older adults, infants, and children are more vulnerable to deeper burns due to thinner skin.<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Partial-thickness (1st degree)<\/strong><\/span><\/td>\r\nInvolves part of the epidermis only.\r\n\r\nInflammation; possible blister formation.\u00a0 Includes sunburns.\r\n\r\nBurn blisters should not be punctured<\/strong> - reduces infection risk and speeds healing.<\/td>\r\n<\/tr>\r\n
Partial-thickness (2nd degree)<\/strong><\/span><\/td>\r\nInvolves epidermis and part of the dermis.\u00a0 Inflammation and blisters present.<\/td>\r\n<\/tr>\r\n
Full-thickness (3rd degree)<\/strong><\/span><\/td>\r\nInvolves epidermis, dermis, and hypodermis (and possibly deeper tissue).\r\n\r\nEschar<\/strong> (dead tissue) is present.\u00a0 May require escharotomy<\/strong> to relieve pressure.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n \r\n\r\n[caption id=\"attachment_2377\" align=\"alignnone\" width=\"300\"]\"First,<\/a> First, second, and third degree burn tissue damage. First degree burns only affect the epidermis (outer layer of skin). There are no blisters, but the skin will appear red, itchy, and dry. Second degree burns affect the epidermis and part of the dermis. The skin will be blistered, swollen, painful, red, white, or splotchy. Third degree burns destroy the epidermis, the entire dermis, and reach the subcutaneous layer. Skin will appear swollen, dry, black, white, brown, or yellowing. Nerve endings are are commonly destroyed with third degree burns, therefore the patient often experiences a lack of pain.[\/caption]\r\n\r\n[caption id=\"attachment_6662\" align=\"alignnone\" width=\"300\"]\"1st<\/a> 1st Degree Burn - Sunburn[\/caption]\r\n\r\n[caption id=\"attachment_6660\" align=\"alignnone\" width=\"300\"]\"2nd<\/a> 2nd Degree Burn Blister.[\/caption]\r\n\r\n[caption id=\"attachment_2559\" align=\"alignnone\" width=\"225\"]\"Skin<\/a> Skin graft performed on the ankle due to third degree burns.[\/caption]\r\n\r\n \r\n
\r\n

Systemic Complications of Severe Burns<\/strong><\/p>\r\n\r\n<\/header>\r\n

\r\n

Dehydration:<\/strong>\u00a0 Large wounds allow significant water evaporation.\u00a0 Controlled by dressings or skin grafting.<\/p>\r\n

Edema:<\/strong>\u00a0 Widespread capillary permeability causes extensive swelling and decreased blood volume.<\/p>\r\n

Hypovolemic shock:<\/strong>\u00a0 Due to dehydration and edema \u2192 insufficient blood pumped \u2192 organ hypoxia \u2192 organ failure.\u00a0 Signs:\u00a0 hypotension, acidosis<\/strong> (from anaerobic respiration producing lactic acid).\u00a0 Pathway:\u00a0 massive inflammation \u2192 vasodilation \u2192 hypotension \u2192 hypoxia \u2192 organ failure \u2192 death.<\/p>\r\n

Anemia:<\/strong>\u00a0 Caused by blood loss from trauma or burns.<\/p>\r\n

Respiratory problems:\u00a0<\/strong> Smoke inhalation \u2192 bronchiole inflammation \u2192 swelling, bronchoconstriction, and impaired gas exchange.<\/p>\r\n

Infection \/ Sepsis:\u00a0<\/strong> Large wounds are highly susceptible to infection and sepsis<\/strong> (infection \u2192 systemic vasodilation\u00a0 \u2192 septic shock \u2192 hypotension \u2192 organ failure \u2192 death).\u00a0 Prophylactic antibiotics are given to reduce chance of infection.<\/p>\r\n

Hypermetabolism:<\/strong>\u00a0 Increased metabolic demands during healing require adequate nutrients, water, and electrolytes.<\/p>\r\nContractures and Adhesions:<\/strong>\u00a0 Scar tissue can form contractures and adhesions that restrict mobility.\u00a0 Treatment can involve physiotherapy during rehabilitation to reduce loss of range of motion associated with scarring.\r\n\r\n<\/div>\r\n<\/div>\r\n

Factors Affecting Wound Healing<\/strong><\/span><\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Oxygenation<\/strong><\/span><\/td>\r\nPoor oxygenation lowers cellular activity and mitotic rates, delaying healing.<\/td>\r\n<\/tr>\r\n
Age<\/strong><\/span><\/td>\r\nOlder adults heal more slowly due to lower cellular activity.\u00a0 Adult females tend to heal faster than adult males.<\/td>\r\n<\/tr>\r\n
Infection<\/strong><\/span><\/td>\r\nProlongs inflammation and delays healing.<\/td>\r\n<\/tr>\r\n
Foreign material<\/strong><\/span><\/td>\r\nDirt, thorns, splinters, and debris delay healing, especially if not removed.<\/td>\r\n<\/tr>\r\n
Underlying illness<\/strong><\/span><\/td>\r\nDiabetes, cancer, and other systemic diseases delay healing.<\/td>\r\n<\/tr>\r\n
Obesity<\/strong><\/span><\/td>\r\nChronic inflammation and reduced vascularity may delay healing.<\/td>\r\n<\/tr>\r\n
Glucocorticoid Use<\/strong><\/span><\/td>\r\nSlows healing due to immunosuppressive and catabolic effects.<\/td>\r\n<\/tr>\r\n
NSAIDs \/ COX-2 drugs<\/strong><\/span><\/td>\r\nCan increase scarring.<\/td>\r\n<\/tr>\r\n
Chemotherapy<\/strong><\/span><\/td>\r\nReduces WBC proliferation, cell division, and angiogenesis - all delaying healing.<\/td>\r\n<\/tr>\r\n
Nutrition deficits<\/strong><\/span><\/td>\r\nReduce proteins, carbohydrates, fats, vitamins, and minerals required for cellular activity and division.<\/td>\r\n<\/tr>\r\n
Alcohol<\/strong><\/span><\/td>\r\nSlows cellular activity, delaying healing<\/td>\r\n<\/tr>\r\n
Smoking<\/strong><\/span><\/td>\r\nCauses vasoconstriction, reducing oxygen and WBC delivery to the wound.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

Problems Associated with Scarring<\/strong><\/span><\/h3>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Loss of function<\/strong><\/span><\/td>\r\nScar tissue lacks hair follicles, sweat and sebaceous glands,<\/strong> and sensory nerve endings<\/strong>.\r\n\r\nNon-regenerative tissues<\/strong> (heart, kidney, pancreas, brain, spinal cord, teeth, articular cartilage, eyes, ears) lose functional cells permanently.<\/td>\r\n<\/tr>\r\n
Non-elasticity<\/strong><\/span><\/td>\r\nInelastic scar tissue limits range of motion<\/strong>.\r\n\r\nLarge burn wounds can cause contractures.<\/strong>\r\n\r\nPhysiotherapy and surgery can partially offset this.<\/td>\r\n<\/tr>\r\n
Adhesions<\/strong><\/span><\/td>\r\nBands of scar tissue<\/strong> between internal organs prevent normal movement (e.g., intestinal twisting and blockage).<\/td>\r\n<\/tr>\r\n
Keloids<\/strong><\/span><\/td>\r\nRaised hypertrophic scar tissue<\/strong> from excessive collagen<\/strong> production.\r\n\r\nStrong genetic predisposition; more common in individuals with darker skin and on the upper chest and back.\r\n\r\nReducible through surgery,<\/strong> laser, cryotherapy, or corticosteroid injection<\/strong>.<\/td>\r\n<\/tr>\r\n
Ulceration<\/strong><\/span><\/td>\r\nScars impairing blood supply cause further tissue damage.\r\n\r\nVery rarely, chronic wound scars can become cancerous ulcers.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n[caption id=\"attachment_2374\" align=\"alignnone\" width=\"300\"]\"Perihepatic<\/a> Perihepatic adhesions (around the liver) following a chlamydia infection. Adhesions are bands of scar tissue that join two internal body surfaces, such as organs or other internal tissues, to each other that normally are not attached.[\/caption]\r\n\r\n[caption id=\"attachment_2375\" align=\"alignnone\" width=\"300\"]\"Bulky<\/a> Bulky keloid forming at the site of abdominal surgery[\/caption]\r\n\r\n[caption id=\"attachment_2376\" align=\"alignnone\" width=\"300\"]\"Ear<\/a> Keloid forming on ear following ear piercing.[\/caption]\r\n\r\n ","rendered":"

Any break in skin in a wound.<\/strong>\u00a0 All wounds progress through four phases:<\/p>\n\n\n\n\n\n\n
1.\u00a0 Hemostasis<\/strong><\/span><\/td>\nCellular damage triggers cytokine release attracting macrophages, neutrophils, platelets, and mast cells.<\/p>\n

Platelet plug and fibrin mesh form to stop bleeding and contain the area.<\/td>\n<\/tr>\n

2.\u00a0 Inflammation<\/strong><\/span><\/td>\nMacrophages and neutrophils remove pathogens and debris.<\/p>\n

Pro-inflammatory mediators<\/strong> (histamine, prostaglandin, bradykinin) induce vasodilation, increased capillary permeability and trigger nociceptors producing the 4 cardinal signs of inflammation (redness, warmth, swelling, and pain).<\/td>\n<\/tr>\n

3.\u00a0 Granulation and Proliferation<\/strong><\/span><\/td>\nActivated cells (fibroblasts, macrophages, epithelial and endothelial cells) release growth factors stimulating angiogenesis<\/strong> and formation of granulation tissue<\/strong> (pink, moist, fragile, highly vascular).<\/p>\n

Fibroblasts<\/strong> produce collagen that crosslink and contracts across the wound to strengthen repair.<\/p>\n

Stem cells<\/strong> undergo mitosis to replace lost cells.<\/td>\n<\/tr>\n

4.\u00a0 Remodeling<\/strong><\/span><\/td>\nCollagen-rich scar tissue may gradually be replaced by epithelial cells over time.<\/p>\n

Extent of remodeling depends on wound dimensions, patient age, health, and genetics.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"Tissue<\/a>
Tissue Healing: During wound repair, collagen fibers are laid down randomly by fibroblasts that move into repair the area.<\/figcaption><\/figure>\n

Three Categories of Wound Healing<\/strong><\/span><\/h3>\n\n\n\n\n\n
Primary (1st) Intention<\/strong><\/span><\/td>\nMinimal-gap, uninfected wounds (e.g., clean surgical incisions).<\/p>\n

Edges approximated with sutures, staples, or adhesive closures.<\/p>\n

Criteria:\u00a0 clean, fresh (within 4-8 hours), free of debris, and necrosis.<\/p>\n

Results in minimal scarring and loss of functional tissue.<\/td>\n<\/tr>\n

Secondary (2nd) Intention<\/strong><\/span><\/td>\nLarger, deeper, or infected wounds where suturing is not feasible.<\/p>\n

Heals from the base outward; cleaned and dressed to prevent infection.<\/p>\n

Results in more granulation tissue, more collagen, greater scare formation and reduced functional structures (fewer hair follicles, glands, sensory nerved endings, melanocytes).<\/td>\n<\/tr>\n

Tertiary (3rd) Intention<\/strong><\/span><\/td>\nA wound healing by 2nd intention is purposely interrupted during granulation to close it mechanically (skin grafts, sutures, staples) after initial treatment of infection and edema.<\/p>\n

In this type of process, debridement may also have been required prior to closing the wound mechanically.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Burn Wounds<\/strong><\/span><\/h3>\n

Burns can be thermal, electrical,<\/strong> or chemical,<\/strong> affecting skin, respiratory tract (smoke inhalation), or digestive tract (chemical ingestion).\u00a0 Severity depends on cause, temperature\/strength\/concentration, duration, body area, and site.\u00a0 Older adults, infants, and children are more vulnerable to deeper burns due to thinner skin.<\/p>\n\n\n\n\n\n
Partial-thickness (1st degree)<\/strong><\/span><\/td>\nInvolves part of the epidermis only.<\/p>\n

Inflammation; possible blister formation.\u00a0 Includes sunburns.<\/p>\n

Burn blisters should not be punctured<\/strong> – reduces infection risk and speeds healing.<\/td>\n<\/tr>\n

Partial-thickness (2nd degree)<\/strong><\/span><\/td>\nInvolves epidermis and part of the dermis.\u00a0 Inflammation and blisters present.<\/td>\n<\/tr>\n
Full-thickness (3rd degree)<\/strong><\/span><\/td>\nInvolves epidermis, dermis, and hypodermis (and possibly deeper tissue).<\/p>\n

Eschar<\/strong> (dead tissue) is present.\u00a0 May require escharotomy<\/strong> to relieve pressure.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

\"First,<\/a>
First, second, and third degree burn tissue damage. First degree burns only affect the epidermis (outer layer of skin). There are no blisters, but the skin will appear red, itchy, and dry. Second degree burns affect the epidermis and part of the dermis. The skin will be blistered, swollen, painful, red, white, or splotchy. Third degree burns destroy the epidermis, the entire dermis, and reach the subcutaneous layer. Skin will appear swollen, dry, black, white, brown, or yellowing. Nerve endings are are commonly destroyed with third degree burns, therefore the patient often experiences a lack of pain.<\/figcaption><\/figure>\n
\"1st<\/a>
1st Degree Burn – Sunburn<\/figcaption><\/figure>\n
\"2nd<\/a>
2nd Degree Burn Blister.<\/figcaption><\/figure>\n
\"Skin<\/a>
Skin graft performed on the ankle due to third degree burns.<\/figcaption><\/figure>\n

 <\/p>\n

\n
\n

Systemic Complications of Severe Burns<\/strong><\/p>\n<\/header>\n

\n

Dehydration:<\/strong>\u00a0 Large wounds allow significant water evaporation.\u00a0 Controlled by dressings or skin grafting.<\/p>\n

Edema:<\/strong>\u00a0 Widespread capillary permeability causes extensive swelling and decreased blood volume.<\/p>\n

Hypovolemic shock:<\/strong>\u00a0 Due to dehydration and edema \u2192 insufficient blood pumped \u2192 organ hypoxia \u2192 organ failure.\u00a0 Signs:\u00a0 hypotension, acidosis<\/strong> (from anaerobic respiration producing lactic acid).\u00a0 Pathway:\u00a0 massive inflammation \u2192 vasodilation \u2192 hypotension \u2192 hypoxia \u2192 organ failure \u2192 death.<\/p>\n

Anemia:<\/strong>\u00a0 Caused by blood loss from trauma or burns.<\/p>\n

Respiratory problems:\u00a0<\/strong> Smoke inhalation \u2192 bronchiole inflammation \u2192 swelling, bronchoconstriction, and impaired gas exchange.<\/p>\n

Infection \/ Sepsis:\u00a0<\/strong> Large wounds are highly susceptible to infection and sepsis<\/strong> (infection \u2192 systemic vasodilation\u00a0 \u2192 septic shock \u2192 hypotension \u2192 organ failure \u2192 death).\u00a0 Prophylactic antibiotics are given to reduce chance of infection.<\/p>\n

Hypermetabolism:<\/strong>\u00a0 Increased metabolic demands during healing require adequate nutrients, water, and electrolytes.<\/p>\n

Contractures and Adhesions:<\/strong>\u00a0 Scar tissue can form contractures and adhesions that restrict mobility.\u00a0 Treatment can involve physiotherapy during rehabilitation to reduce loss of range of motion associated with scarring.<\/p>\n<\/div>\n<\/div>\n

Factors Affecting Wound Healing<\/strong><\/span><\/h3>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Oxygenation<\/strong><\/span><\/td>\nPoor oxygenation lowers cellular activity and mitotic rates, delaying healing.<\/td>\n<\/tr>\n
Age<\/strong><\/span><\/td>\nOlder adults heal more slowly due to lower cellular activity.\u00a0 Adult females tend to heal faster than adult males.<\/td>\n<\/tr>\n
Infection<\/strong><\/span><\/td>\nProlongs inflammation and delays healing.<\/td>\n<\/tr>\n
Foreign material<\/strong><\/span><\/td>\nDirt, thorns, splinters, and debris delay healing, especially if not removed.<\/td>\n<\/tr>\n
Underlying illness<\/strong><\/span><\/td>\nDiabetes, cancer, and other systemic diseases delay healing.<\/td>\n<\/tr>\n
Obesity<\/strong><\/span><\/td>\nChronic inflammation and reduced vascularity may delay healing.<\/td>\n<\/tr>\n
Glucocorticoid Use<\/strong><\/span><\/td>\nSlows healing due to immunosuppressive and catabolic effects.<\/td>\n<\/tr>\n
NSAIDs \/ COX-2 drugs<\/strong><\/span><\/td>\nCan increase scarring.<\/td>\n<\/tr>\n
Chemotherapy<\/strong><\/span><\/td>\nReduces WBC proliferation, cell division, and angiogenesis – all delaying healing.<\/td>\n<\/tr>\n
Nutrition deficits<\/strong><\/span><\/td>\nReduce proteins, carbohydrates, fats, vitamins, and minerals required for cellular activity and division.<\/td>\n<\/tr>\n
Alcohol<\/strong><\/span><\/td>\nSlows cellular activity, delaying healing<\/td>\n<\/tr>\n
Smoking<\/strong><\/span><\/td>\nCauses vasoconstriction, reducing oxygen and WBC delivery to the wound.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Problems Associated with Scarring<\/strong><\/span><\/h3>\n\n\n\n\n\n\n\n
Loss of function<\/strong><\/span><\/td>\nScar tissue lacks hair follicles, sweat and sebaceous glands,<\/strong> and sensory nerve endings<\/strong>.<\/p>\n

Non-regenerative tissues<\/strong> (heart, kidney, pancreas, brain, spinal cord, teeth, articular cartilage, eyes, ears) lose functional cells permanently.<\/td>\n<\/tr>\n

Non-elasticity<\/strong><\/span><\/td>\nInelastic scar tissue limits range of motion<\/strong>.<\/p>\n

Large burn wounds can cause contractures.<\/strong><\/p>\n

Physiotherapy and surgery can partially offset this.<\/td>\n<\/tr>\n

Adhesions<\/strong><\/span><\/td>\nBands of scar tissue<\/strong> between internal organs prevent normal movement (e.g., intestinal twisting and blockage).<\/td>\n<\/tr>\n
Keloids<\/strong><\/span><\/td>\nRaised hypertrophic scar tissue<\/strong> from excessive collagen<\/strong> production.<\/p>\n

Strong genetic predisposition; more common in individuals with darker skin and on the upper chest and back.<\/p>\n

Reducible through surgery,<\/strong> laser, cryotherapy, or corticosteroid injection<\/strong>.<\/td>\n<\/tr>\n

Ulceration<\/strong><\/span><\/td>\nScars impairing blood supply cause further tissue damage.<\/p>\n

Very rarely, chronic wound scars can become cancerous ulcers.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"Perihepatic<\/a>
Perihepatic adhesions (around the liver) following a chlamydia infection. Adhesions are bands of scar tissue that join two internal body surfaces, such as organs or other internal tissues, to each other that normally are not attached.<\/figcaption><\/figure>\n
\"Bulky<\/a>
Bulky keloid forming at the site of abdominal surgery<\/figcaption><\/figure>\n
\"Ear<\/a>
Keloid forming on ear following ear piercing.<\/figcaption><\/figure>\n

 <\/p>\n

Media Attributions<\/h2>