Wound contraction occurs to a much greater extent in secondary healing than in primary healing. The maximal tensile strength of the incision wound occurs after about 11 to 14 weeks. Wounds generally heal in 4 to 6 weeks. Chronic wounds are those that fail to heal within this timeframe. Many factors can lead to impaired healing. The primary factors are hypoxia, bacterial colonization, ischemia, reperfusion injury, altered cellular response, and collagen synthesis defects. These may be the result of a systemic illness, such as diabetes, or chronic conditions, such as smoking or malnutrition.
Local factors that can impair wound healing are pressure, tissue edema, hypoxia, infection, maceration, and dehydration. Bacterial biofilm, which is a slime created by a bacterial community to protect against host defenses and allow bacterial proliferation, is another inhibitory factor of wounding healing. Biofilm can produce a low oxygen, low pH environment for the wound. This film also can create a physical barrier which prevents cellular migration and prevents antibiotic and antibody penetration.
Clinical considerations in wound management include preventing and controlling infection and contamination, maintaining adequate moisture, treating edema, and preventing further injury. Wounds should be cleansed prior to closure. Wounds can be cleansed with either irrigation or scrubbed and irrigated with 0. Alternately, wounds can be scrubbed with pluronic plyols and irrigated with normal saline.http://unidentified.webd.pl/piercing/miscellaneous/understanding-criminal-justice-in-hong-kong.php
Tap water is frequently used by patients to irrigate wounds prior to seeking out medical attention. The advantage is that copious amounts of irrigant can be rapidly used, however, irrigation pressure may be difficult to control. A study by Mosacati found that infection rates for wounds irrigated with tap water were comparable to those irrigated by a 0. Wound dressings should create a moist environment to prevent wound desiccation but allows for absorption of additional exudate.
It should allow for air flow, prevent particulate contamination, and be impermeable to bacteria or microbiota. There are several techniques used to reconstruct or surgically repair wounds, the simplest of which is primary closure. Other techniques are closure via secondary intention, negative pressure wound therapy, and grafting. To access free multiple choice questions on this topic, click here.
Wound healing - Wikipedia
This book is distributed under the terms of the Creative Commons Attribution 4. Turn recording back on. National Center for Biotechnology Information , U. StatPearls Publishing; Jan-. Show details Treasure Island FL: StatPearls Publishing ; Jan-. Wound, Healing, Phases Heather A. Introduction Wound healing is a natural physiological reaction to tissue injury.
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The maturation and remodeling phase is where the wound achieves maximum strength as it matures. Function When an injury occurs, the initial phase is always an outpouring of lymphatic fluid and blood. Issues of Concern Wounds generally heal in 4 to 6 weeks. Clinical Significance Clinical considerations in wound management include preventing and controlling infection and contamination, maintaining adequate moisture, treating edema, and preventing further injury.
Other Issues Wound dressings should create a moist environment to prevent wound desiccation but allows for absorption of additional exudate. Transforming growth factor and several other cytokines all have a role in healing but when to add or how much of the cytokine is needed for adequate healing is still being debated. Hyperbaric oxygen can promote healing, but the technique and success rate is not well established. Even though there are many anecdotal reports on honey and wound healing, controlled studies show that the benefits of honey are marginal at best.
Finally, medications that can adversely affect healing include anticonvulsants, steroids, antibiotics, angiogenesis inhibitors and NSAIDs. Drugs known to promote healing include insulin, vitamins, thyroid hormone and iron. Questions To access free multiple choice questions on this topic, click here.
A morphoelastic model for dermal wound closure. Advances in the treatment of chronic wounds: Expert Opin Ther Pat. Wound healing in urology. Biological perspectives of delayed fracture healing. PMC ] [ PubMed: Br J Community Nurs. Choosing Tap Water vs. The formation of granulation tissue into an open wound allows the reepithelialization phase to take place, as epithelial cells migrate across the new tissue to form a barrier between the wound and the environment.
In healing that results in a scar, sweat glands, hair follicles   and nerves do not form. With the lack of hair follicles, nerves and sweat glands, the wound, and the resulting healing scar, provide a challenge to the body with regards to temperature control. Keratinocytes migrate without first proliferating. However, epithelial cells require viable tissue to migrate across, so if the wound is deep it must first be filled with granulation tissue.
If the basement membrane is not breached, epithelial cells are replaced within three days by division and upward migration of cells in the stratum basale in the same fashion that occurs in uninjured skin. Migration of keratinocytes over the wound site is stimulated by lack of contact inhibition and by chemicals such as nitric oxide. Before they begin migrating, keratinocytes change shape, becoming longer and flatter and extending cellular processes like lamellipodia and wide processes that look like ruffles.
Epithelial cells climb over one another in order to migrate. These basal cells continue to migrate across the wound bed, and epithelial cells above them slide along as well. Fibrin , collagen, and fibronectin in the ECM may further signal cells to divide and migrate. Like fibroblasts, migrating keratinocytes use the fibronectin cross-linked with fibrin that was deposited in inflammation as an attachment site to crawl across.
As keratinocytes migrate, they move over granulation tissue but stay underneath the scab, thereby separating the scab from the underlying tissue. Because they must dissolve any scab that forms, keratinocyte migration is best enhanced by a moist environment, since a dry one leads to formation of a bigger, tougher scab. Cells can only migrate over living tissue,  so they must excrete collagenases and proteases like matrix metalloproteinases MMPs to dissolve damaged parts of the ECM in their way, particularly at the front of the migrating sheet. As keratinocytes continue migrating, new epithelial cells must be formed at the wound edges to replace them and to provide more cells for the advancing sheet.
Growth factors, stimulated by integrins and MMPs, cause cells to proliferate at the wound edges. Keratinocytes themselves also produce and secrete factors, including growth factors and basement membrane proteins, which aid both in epithelialization and in other phases of healing. Keratinocytes continue migrating across the wound bed until cells from either side meet in the middle, at which point contact inhibition causes them to stop migrating.
Contraction is a key phase of wound healing with repair. If contraction continues for too long, it can lead to disfigurement and loss of function. Contraction commences approximately a week after wounding, when fibroblasts have differentiated into myofibroblasts. At first, contraction occurs without myofibroblast involvement.
Myofibroblasts, which are similar to smooth muscle cells, are responsible for contraction. Myofibroblasts are attracted by fibronectin and growth factors and they move along fibronectin linked to fibrin in the provisional ECM in order to reach the wound edges. Also, at an adhesion called the fibronexus , actin in the myofibroblast is linked across the cell membrane to molecules in the extracellular matrix like fibronectin and collagen.
As the actin in myofibroblasts contracts, the wound edges are pulled together. Fibroblasts lay down collagen to reinforce the wound as myofibroblasts contract. When the levels of collagen production and degradation equalize, the maturation phase of tissue repair is said to have begun. As the phase progresses, the tensile strength of the wound increases. The phases of wound healing normally progress in a predictable, timely manner; if they do not, healing may progress inappropriately to either a chronic wound  such as a venous ulcer or pathological scarring such as a keloid scar.
Many factors controlling the efficacy, speed, and manner of wound healing fall under two types: Up until about , the classic paradigm of wound healing, involving stem cells restricted to organ-specific lineages, had never been seriously challenged. Since then, the notion of adult stem cells having cellular plasticity or the ability to differentiate into non-lineage cells has emerged as an alternative explanation.
Multipotent adult stem cells have the capacity to be self-renewing and give rise to different cell types. Stem cells give rise to progenitor cells, which are cells that are not self-renewing, but can generate several types of cells. The extent of stem cell involvement in cutaneous skin wound healing is complex and not fully understood. It is thought that the epidermis and dermis are reconstituted by mitotically active stem cells that reside at the apex of rete ridges basal stem cells or BSC , the bulge of hair follicles hair follicular stem cell or HFSC , and the papillary dermis dermal stem cells.
In rare circumstances, such as extensive cutaneous injury, self-renewal subpopulations in the bone marrow are induced to participate in the healing process, whereby they give rise to collagen-secreting cells that seem to play a role during wound repair. Bone marrow also harbors a progenitor subpopulation endothelial progenitor cells or EPC that, in the same type of setting, are mobilized to aid in the reconstruction of blood vessels.
After injury, structural tissue heals with incomplete or complete regeneration. An example of complete regeneration without an interruption of the morphology is non-injured tissue, such as skin. There is a subtle distinction between 'repair' and 'regeneration'. An example of a tissue regenerating completely after an interruption of morphology is the endometrium ; the endometrium after the process of breakdown via the menstruation cycle heals with complete regeneration. In some instances, after a tissue breakdown, such as in skin, a regeneration closer to complete regeneration may be induced by the use of biodegradable collagen - glycoaminoglycan scaffolds.
Skin Wound Healing
Pharmaceutical agents have been investigated which may be able to turn off myofibroblast differentiation. A new way of thinking derived from the notion that heparan sulfates are key player in tissue homeostasis: In wound areas, tissue homeostasis is lost as the heparan sulfates are degraded preventing the replacement of dead cells by identical cells. Heparan sulfate analogues cannot be degraded by all know heparanases and glycanases and bind to the free heparin sulfate binding spots on the ECM, therefore preserving the normal tissue homeostasis and preventing scarring. Repair or regeneration with regards to hypoxia-inducible factor 1-alpha HIF-1a.
Scientists found that the simple up-regulation of HIF-1a via PHD inhibitors regenerates lost or damaged tissue in mammals that have a repair response; and the continued down-regulation of Hif-1a results in healing with a scarring response in mammals with a previous regenerative response to the loss of tissue. The act of regulating HIF-1a can either turn off, or turn on the key process of mammalian regeneration.
Scarless healing is sometimes mixed up with the concept of scar free healing , which is wound healing which results in absolutely no scar free of scarring. However they are different concepts. A reverse to scarless wound healing is scarification wound healing to scar more. Historically, certain cultures consider scarification attractive;  however, this is generally not the case in the modern western society, in which many patients are turning to plastic surgery clinics with unrealistic expectations.
Many of these treatments may only have a placebo effect , and the evidence base for the use of many current treatments is poor. Since the s, comprehension of the basic biologic processes involved in wound repair and tissue regeneration have expanded due to advances in cellular and molecular biology.
Scarless wound healing only occurs in mammalian foetal tissues  and complete regeneration is limited to lower vertebrates, such as salamanders , and invertebrates. Clues as to how this might be achieved come from studies of wound healing in embryos, where repair is fast and efficient and results in essentially perfect regeneration of any lost tissue. The etymology of the term scarless wound healing has a long history. This process involved cutting in a surgical slant, instead of a right angle…; it was described in various Newspapers.
After inflammation, restoration of normal tissue integrity and function is preserved by feedback interactions between diverse cell types mediated by adhesion molecules and secreted cytokines. Disruption of normal feedback mechanisms in cancer threatens tissue integrity and enables a malignant tumor to escape the immune system.
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Considerable effort has been devoted to understanding the physical relationships governing wound healing and subsequent scarring, with mathematical models and simulations developed to elucidate these relationships. The alignment of collagen describes the degree of scarring; basket-weave orientation of collagen is characteristic of normal skin, whereas aligned collagen fibers lead to significant scarring. The growth of tissue can be simulated using the aforementioned relationships from a biochemical and biomechanical point of view.
The biologically active chemicals that play an important role in wound healing are modeled with Fickian diffusion to generate concentration profiles. The balance equation for open systems when modeling wound healing incorporates mass growth due to cell migration and proliferation. Here the following equation is used:. Successful wound healing is dependent on various cell types, molecular mediators and structural elements. Primary intention is the healing of a clean wound without tissue loss.
Wound closure is performed with sutures stitches , staples, or adhesive tape or glue. Primary intention can only be implemented when the wound is precise and there is minimal disruption to the local tissue and the epithelial basement membrane, e. This process is faster than healing by secondary intention. If the wound edges are not reapproximated immediately, delayed primary wound healing transpires.
This type of healing may be desired in the case of contaminated wounds. By the fourth day, phagocytosis of contaminated tissues is well underway, and the processes of epithelization, collagen deposition, and maturation are occurring. Foreign materials are walled off by macrophages that may metamorphose into epithelioid cells, which are encircled by mononuclear leukocytes, forming granulomas.
Usually the wound is closed surgically at this juncture, and if the "cleansing" of the wound is incomplete, chronic inflammation can ensue, resulting in prominent scarring. Following are the main growth factors involved in wound healing:. Advancements in the clinical understanding of wounds and their pathophysiology have commanded significant biomedical innovations in the treatment of acute, chronic, and other types of wounds.
Many biologics, skin substitutes, biomembranes and scaffolds have been developed to facilitate wound healing through various mechanisms. From Wikipedia, the free encyclopedia. Hand abrasion Approximate days since injury 0 3 17 30 Wound healing is a complex process in which the skin, and the tissues under it, repair themselves after injury. This section may require cleanup to meet Wikipedia's quality standards. No cleanup reason has been specified.
Please help improve this section if you can. April Learn how and when to remove this template message. Collective cell migration Dressing medical History of wound care Regeneration in humans Wound bed preparation Wound licking Scar free healing. Biomaterials for Treating Skin Loss. Orgill DP, Blanco C editors. Cell biochemistry and function. American journal of surgery. European Heart Journal Supplements.
New York Marcel Dekker, Inc. Cellular, molecular and biochemical differences in the pathophysiology of healing between acute wounds, chronic wounds and wounds in the elderly. Retrieved 31 January Archived from the original on 25 April Retrieved 16 March Wound Healing, Growth Factors.
Accessed January 20, Mechanisms of Ageing and Development. The care of wounds: A guide for nurses. Clinical Techniques in Equine Practice. Trends in Cell Biology. The phases of cutaneous wound healing. Journal of Postgraduate Medicine. Much more than just giant phagocytes". Macrophages are present essentially in all tissues, beginning with embryonic development and, in addition to their role in host defense and in the clearance of apoptotic cells, are being increasingly recognized for their trophic function and role in regeneration.
Indications and best use". Biology, Pathology, and Management. Stanford University Medical Center. European Journal of Cell Biology. Researchers have identified a cell that aids limb regrowth in Salamanders. Macrophages are a type of repairing cell that devour dead cells and pathogens, and trigger other immune cells to respond to pathogens. Proceedings of the National Academy of Sciences. Accessed September 15, Accessed December 27, International Journal of Experimental Pathology.
Wound Repair and Regeneration. Advanced Drug Delivery Reviews. The cellular, biochemical, and mechanical phases of wound healing. Charles Brunicardi; Dana K. Andersen; Billiar, Timothy R. Schwartz's Principles of Surgery, Ninth Edition. Methods in Molecular Medicine. Retrieved 13 July When the dermis is destroyed, the scars do not regrow hair, nerves or sweat glands, providing additional challenges to body temperature control. Archives of Oral Biology. Cutaneous trauma and its treatment. In, Textbook of Military Medicine: Office of the Surgeon General, Department of the Army.
Virtual Naval Hospital Project. Accessed through web archive on September 15, The American Journal of Surgery.