4. Physiology of Healing

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4. Physiology of Healing

The physiology of wound healing is a complex and highly coordinated process involving a series of cellular and biochemical events. Wound healing is a dynamic process that occurs in three distinct but overlapping phases: inflammation, proliferation, and remodeling.

Inflammatory Phase

The inflammatory phase is the first step in the healing process. It starts immediately after the injury and lasts from 2 to 5 days. In this phase, vasoconstriction occurs, which is an immediate response to injury to control bleeding. Then, vasodilation occurs, which allows the arrival of inflammatory cells, such as neutrophils and macrophages, to the site of injury. Neutrophils are the first to arrive and their main function is to eliminate bacteria and cellular debris, while macrophages are responsible for the phagocytosis of bacteria and remaining cellular debris and for the release of growth factors that promote the migration and proliferation of cells such as fibroblasts and endothelial cells.

Proliferative Phase

The proliferative phase is the second stage of the healing process and lasts from 2 to 21 days. In this phase, the formation of granulation tissue occurs, which is a temporary repair tissue, extremely vascularized and rich in fibroblasts and inflammatory cells. Fibroblasts are the main cells involved in the production of collagen, which is the main protein of the extracellular matrix and which provides strength and integrity to scar tissue. Also, in this phase, epithelialization occurs, which is the process by which epithelial cells migrate over the granulation tissue to close the wound.

Remodeling Phase

The remodeling phase is the last step in the healing process and can last from 21 days to 2 years. In this phase, collagen remodeling occurs, which is a process that transforms the collagen initially deposited in a disorganized way into a more organized and resistant collagen. This process is mediated by enzymes called matrix metalloproteinases (MMPs), which are produced by fibroblasts and whose function is to degrade disorganized collagen and allow the deposition of more organized and resistant collagen.

In addition, in this phase, wound contraction occurs, which is a process that reduces the size of the wound through the action of specialized cells called myofibroblasts. Myofibroblasts have the ability to contract, similar to muscle cells, and thus decrease the size of the wound.

In summary, the physiology of wound healing is a complex process involving a series of highly coordinated cellular and biochemical events. Understanding this process is essential for proper wound management and for promoting efficient and effective healing.

It is important to note that any alteration or interruption in any of these phases can result in slow healing or inadequate healing, resulting in hypertrophic scars, keloids or chronic wounds. Therefore, knowledge about the physiology of healing is essential for nursing practice in wound and dressing care.

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184.1. Physiology of Healing: Phases of Healing