Wound healing, or cicatrisation, is an intricate process in which the skin (or another organ-tissue) repairs itself after injury. In normal skin, the epidermis (outermost layer) and dermis (inner or deeper layer) exists in a steady-state equilibrium, forming a protective barrier against the external environment. Once the protective barrier is broken, the normal (physiologic) process of wound healing is immediately set in motion. The classic model of wound healing is divided into three or four sequential, yet overlapping, phases: (1) hemostasis (not considered a phase by some authors), (2) inflammatory, (3) proliferative and (4) remodeling. Upon injury to the skin, a set of complex biochemical events takes place in a closely orchestrated cascade to repair the damage. Within minutes post-injury, platelets (thrombocytes) aggregate at the injury site to form a fibrin clot. This clot acts to control active bleeding (hemostasis). The speed of wound healing can be impacted by many factors, including the bloodstream levels of hormones such as oxytocin.
In the inflammatory phase, bacteria and debris are phagocytosed and removed, and factors are released that cause the migration and division of cells involved in the proliferative phase.
The proliferative phase is characterized by angiogenesis, collagen deposition, granulation tissue formation, epithelialization, and wound contraction. In angiogenesis, new blood vessels are formed by vascular endothelial cells. In fibroplasia and granulation tissue formation, fibroblasts grow and form a new, provisional extracellular matrix (ECM) by excreting collagen and fibronectin. Concurrently, re-epithelialization of the epidermis occurs, in which epithelial cells proliferate and 'crawl' atop the wound bed, providing cover for the new tissue.
In contraction, the wound is made smaller by the action of myofibroblasts, which establish a grip on the wound edges and contract themselves using a mechanism similar to that in smooth muscle cells. When the cells' roles are close to complete, unneeded cells undergo apoptosis.
In the maturation and remodeling phase, collagen is remodeled and realigned along tension lines and cells that are no longer needed are removed by apoptosis.
However, this process is not only complex but fragile, and susceptible to interruption or failure leading to the formation of non-healing chronic wounds. Factors which may contribute to this include diabetes, venous or arterial disease, old age, and infection.
Read more about Wound Healing: Early Vs Cellular Phase, Inflammatory Phase, Proliferative Phase, Maturation and Remodeling, Factors Affecting Wound Healing, Research and Development, Simulating Wound Healing From A Growth Perspective, Overview of Involved Growth Factors
... is highly expressed at sites of inflammation and wound repair, and is associated with diseases involving chronic inflammation and tissue injury ... Wound healing and fibrosis In skin wound healing, CYR61 is highly expressed in the granulation tissue by myofibroblasts, which proliferate and rapidly synthesize ECM ... In skin wounds, CYR61 accumulates in the granulation tissue as myofibroblasts proliferate, and eventually reaches a sufficiently high level to drive the myofibroblasts themselves into senescence, whereupon these cells ...
... The immune system also plays a role in stress and the early stages of wound healing ... repair and promoting recruitment of certain cells to the wound area ... with Alzheimer’s Disease leads to delayed wound healing ...
... are many Deficient Scar Formation Result in wound dehiscence or rupture of the wound due to inadequate formation of granulation tissue ...
... 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 ...
... Wound healing is a localized event involving the reaction of cells to the damage sustained ... Because of this extracellular matrix is often considered as a 'conductor of the wound healing symphony' ... recruit and activate fibroblasts which in subsequent granulation phase migrate into the wound, laying down new collagen of the subtypes I and III ...
Famous quotes containing the words healing and/or wound:
“The example of America must be the example, not merely of peace because it will not fight, but of peace because it is the healing and elevating influence of the world, and strife is not. There is such a thing as a man being too proud to fight. There is such a thing as a nation being so right that it does not need to convince others by force that it is right.”
—Woodrow Wilson (18561924)
“But even suppose blood should flow. Is there not a sort of blood shed when the conscience is wounded? Through this wound a mans real manhood and immortality flow out, and he bleeds to an everlasting death. I see this blood flowing now.”
—Henry David Thoreau (18171862)