How a wound heals itself Sarthak Sinha
The largest organ in your bodyisn't your liver or your brain. It's your skin, with a surface areaof about 20 square feet in adults. Though different areas of the skinhave different characteristics, much of this surface performssimilar functions, such as sweating, feeling heat and cold,and growing hair. But after a deep cut or wound, the newly healed skin will look differentfrom the surrounding area, and may not fully regain all its abilities for a while, or at all.
To understand why this happens, we need tolook at the structure of the human skin. The top layer, called the epidermis, consists mostly of hardened cells,called keratinocytes, and provides protection. Since its outer layer is constantly beingshed and renewed, it's pretty easy to repair. But sometimes a wound penetratesinto the dermis, which contains blood vesselsand the various glands and nerve endings
that enable the skin's many functions. And when that happens, it triggers thefour overlapping stages of the regenerative process. The first stage, hemostasis, is the skin'sresponse to two immediate threats: that you're now losing blood and that the physical barrier of the epidermis has been compromised. As the blood vessels tighten to minimizethe bleeding, in a process known as vasoconstriction,
both threats are averted by forminga blood clot. A special protein known as fibrin formscrosslinks on the top of the skin, preventing blood from flowing outand bacteria or pathogens from getting in. After about three hours of this,the skin begins to turn red, signaling the next stage, inflammation. With bleeding under controland the barrier secured, the body sends special cells to fight anypathogens that may have gotten through. Among the most important of theseare white blood cells,
known as macrophages, which devour bacteria and damage tissuethrough a process known as phagocytosis, in addition to producing growth factorsto spur healing. And because these tiny soldiers need to travel through the blood to get to the wound site, the previously constricted blood vessels now expand in a process called vasodilation. About two to three days after the wound,
the proliferative stage occurs, when fibroblast cells begin to enter the wound. In the process of collagen deposition, they produce a fibrous protein called collagen in the wound site, forming connective skin tissueto replace the fibrin from before. As epidermal cells divide to reformthe outer layer of skin, the dermis contracts to close the wound. Finally, in the fourth stage of remodeling, the wound matures as the newly depositedcollagen is rearranged and converted