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With physical trauma or disease suffered by an organism, healing involves the repairing of damaged tissue(s), organs and the biological system as a whole and resumption of (normal) functioning. Medicine includes the process by which the cells in the toàn thân regenerate and repair đồ sộ reduce the size of a damaged or necrotic area and replace it with new living tissue. The replacement can happen in two ways: by regeneration in which the necrotic cells are replaced by new cells that size "like" tissue as was originally there; or by repair in which injured tissue is replaced with scar tissue. Most organs will heal using a mixture of both mechanisms.
Within surgery, healing is more often referred đồ sộ as recovery, and postoperative recovery has historically been viewed simply as restitution of function and readiness for discharge. More recently, it has been described as an energy‐requiring process đồ sộ decrease physical symptoms, reach a level of emotional well‐being, regain functions, and re‐establish activities
Healing is also referred đồ sộ in the context of the grieving process.
In psychiatry and psychology, healing is the process by which neuroses and psychoses are resolved đồ sộ the degree that the client is able đồ sộ lead a normal or fulfilling existence without being overwhelmed by psychopathological phenomena. This process may involve psychotherapy, pharmaceutical treatment or alternative approaches such as traditional spiritual healing.
In order for an injury đồ sộ be healed by regeneration, the cell type that was destroyed must be able đồ sộ replicate. Cells also need a collagen framework along which đồ sộ grow. Alongside most cells there is either a basement membrane or a collagenous network made by fibroblasts that will guide the cells' growth. Since ischaemia and most toxins bởi not destroy collagen, it will continue đồ sộ exist even when the cells around it are dead.
Acute tubular necrosis (ATN) in the kidney is a case in which cells heal completely by regeneration. ATN occurs when the epithelial cells that line the kidney are destroyed by either a lack of oxygen (such as in hypovolemic shock, when blood supply đồ sộ the kidneys is dramatically reduced), or by toxins (such as some antibiotics, heavy metals or carbon tetrachloride).
Although many of these epithelial cells are dead, there is typically patchy necrosis, meaning that there are patches of epithelial cells still alive. In addition, the collagen framework of the tubules remains completely intact.
The existing epithelial cells can replicate, and, using the basement membrane as a guide, eventually bring the kidney back đồ sộ normal. After regeneration is complete, the damage is undetectable, even microscopically.
Healing must happen by repair in the case of injury đồ sộ cells that are unable đồ sộ regenerate (e.g. neurons). Also, damage đồ sộ the collagen network (e.g. by enzymes or physical destruction), or its total collapse (as can happen in an infarct) cause healing đồ sộ take place by repair.
Many genes play a role in healing. For instance, in wound healing, P21 has been found đồ sộ allow mammals đồ sộ heal spontaneously. It even allows some mammals (like mice) đồ sộ heal wounds without scars. The LIN28 ren also plays a role in wound healing. It is dormant in most mammals. Also, the proteins MG53 and TGF beta 1 play important roles in wound healing.
In response đồ sộ an incision or wound, a wound healing cascade is unleashed. This cascade takes place in four phases: clot formation, inflammation, proliferation, and maturation.
Healing of a wound begins with clot formation đồ sộ stop bleeding and đồ sộ reduce infection by bacteria, viruses and fungi. Clotting is followed by neutrophil invasion three đồ sộ 24 hours after the wound has been incurred, with mitoses beginning in epithelial cells after 24 đồ sộ 48 hours.
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In the inflammatory phase, macrophages and other phagocytic cells kill bacteria, debride damaged tissue and release chemical factors such as growth hormones that encourage fibroblasts, epithelial cells and endothelial cells which make new capillaries đồ sộ migrate đồ sộ the area and divide.
In the proliferative phase, immature granulation tissue containing plump, active fibroblasts forms. Fibroblasts quickly produce abundant type III collagen, which fills the defect left by an open wound. Granulation tissue moves, as a wave, from the border of the injury towards the center.
As granulation tissue matures, the fibroblasts produce less collagen and become more spindly in appearance. They begin đồ sộ produce the much stronger type I collagen. Some of the fibroblasts mature into myofibroblasts which contain the same type of actin found in smooth muscle, which enables them đồ sộ contract and reduce the size of the wound.
During the maturation phase of wound healing, unnecessary vessels formed in granulation tissue are removed by apoptosis, and type III collagen is largely replaced by type I. Collagen which was originally disorganized is cross-linked and aligned along tension lines. This phase can last a year or longer. Ultimately a scar made of collagen, containing a small number of fibroblasts is left.
Tissue damaged by inflammation
After inflammation has damaged tissue (when combatting bacterial infection for example) and pro-inflammatory eicosanoids have completed their function, healing proceeds in 4 phases.
In the recall phase the adrenal glands increase production of cortisol which shuts down eicosanoid production and inflammation.
In the Resolution phase, pathogens and damaged tissue are removed by macrophages (white blood cells). Red blood cells are also removed from the damaged tissue by macrophages. Failure đồ sộ remove all of the damaged cells and pathogens may retrigger inflammation. The two subsets of macrophage M1 & M2 plays a crucial role in this phase, M1 macrophage being a pro inflammatory while as M2 is a regenerative and the plasticity between the two subsets determine the tissue inflammation or repair.
In the Regeneration phase, blood vessels are repaired and new cells size in the damaged site similar đồ sộ the cells that were damaged and removed. Some cells such as neurons and muscle cells (especially in the heart) are slow đồ sộ recover.
In the Repair phase, new tissue is generated which requires a balance of anti-inflammatory and pro-inflammatory eicosanoids. Anti-inflammatory eicosanoids include lipoxins, epi-lipoxins, and resolvins, which cause release of growth hormones.
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- ^ Allvin, Renée; Berg, Katarina; Idvall, Ewa; Nilsson, Ulrica (March 2007). "Postoperative recovery: a concept analysis". Journal of Advanced Nursing. 57 (5): 552–558. doi:10.1111/j.1365-2648.2006.04156.x. ISSN 0309-2402. PMID 17284272.
- ^ McBrearty BA, Clark LD, Zhang XM, Blankenhorn EP, Heber-Katz E (1998). "Genetic analysis of a mammalian wound-healing trait". Proc Natl Acad Sci U S A. 95 (20): 11792–7. Bibcode:1998PNAS...9511792M. doi:10.1073/pnas.95.20.11792. PMC 21719. PMID 9751744.
- ^ "Genetic discovery promises healing without scars". the Guardian. March 15, 2010.
- ^ Bedelbaeva, Khamilia; Snyder, Andrew; Gourevitch, Dmitri; Clark, Lise; Zhang, Xiang-Ming; Leferovich, John; Cheverud, James M.; Lieberman, Paul; Heber-Katz, Ellen (March 30, 2010). "Lack of p21 expression links cell cycle control and appendage regeneration in mice". Proceedings of the National Academy of Sciences. 107 (13): 5845–5850. Bibcode:2010PNAS..107.5845B. doi:10.1073/pnas.1000830107. PMC 2851923. PMID 20231440.
- ^ Maron, Dina Fine. "New Limb Regeneration Insight Surprises Scientists". Scientific American.
- ^ "Gene identified that helps wound healing: New research on ren that regulates healing and may control scarring". ScienceDaily.
- ^ The Anti-Inflammation Zone, Barry Sears, pages 230-233, 2005.
- How wounds heal and tumors size With this simple Flash demonstration, Harvard professor Donald Ingber explains how wounds heal, why scars size, and how tumors develop. Presented by Children's Hospital Boston.
- Wound Healing and Repair
- Lorenz H.P. and Longaker M.T. Wounds: Biology, Pathology, and Management. Stanford University Medical Center.
- Romo T. and McLaughlin L.A. 2003. Wound Healing, Skin. Emedicine.com.
- Rosenberg L. and de la Torre J. 2003. Wound Healing, Growth Factors. Emedicine.com.
- After the Injury- Children's Hospital Of Philadelphia