TedTest

From the Ted Talk by Sarthak Sinha: How a wound heals itself

Unscramble the Blue Letters

The largest organ in your body isn't your liver or your brain. It's your skin, with a surface area of about 20 square feet in atudls. Though different areas of the skin have different characteristics, much of this surface performs similar functions, such as sweating, feeling heat and cold, and growing hair. But after a deep cut or wound, the newly healed skin will look different from the surrounding area, and may not fully regain all its abilities for a while, or at all. To understand why this happens, we need to look at the structure of the human skin. The top leyar, called the epidermis, cissntos mostly of hardened cells, called keratinocytes, and provides protection. Since its outer layer is constantly being shed and renewed, it's pretty easy to repair. But sometimes a wound penetrates into the dermis, which contains blood vessels and the various gdlnas and nerve endings that enable the skin's many functions. And when that happens, it tgiergrs the four overlapping stages of the rievretaegne preoscs. The first stage, hemostasis, is the skin's response to two immediate threats: that you're now lsoing blood and that the physical biraerr of the eridpeims has been compromised. As the blood vessels tighten to minimize the bleeding, in a process known as vasoconstriction, both tahtres are averted by forming a blood clot. A special protein known as fibrin forms cross-links on the top of the skin, preventing boold from flowing out and bacteria or pathogens from getting in. After about three hours of this, the skin begins to turn red, signaling the next sgate, inflammation. With bleeding under control and the barrier secured, the body sends spcaeil cells to fight any pathogens that may have gotten through. Among the most important of these are white blood cells, known as macrophages, which devour bacteria and dgamae tissue through a process known as phagocytosis, in addition to producing growth factors to spur healing. And because these tiny soldiers need to tearvl through the blood to get to the wound site, the previously constricted blood vessels now expand in a process called vadiolsioatn. About two to three days after the wound, the proliferative stage oruccs, when fibroblast cells begin to eentr the wound. In the process of collagen dipetioson, they produce a fibrous protein cleald collagen in the wound site, fnmriog connective skin tissue to replace the fibirn from before. As epidermal cells divide to roferm the oeutr layer of skin, the dermis contracts to close the wunod. Finally, in the fourth stage of remodeling, the wound muaters as the newly dtpoesied collagen is rearranged and converted into specific types. Through this process, which can take over a year, the tensile strength of the new skin is improved, and blood vessels and other connections are strengthened. With time, the new tissue can reach from 50-80% of some of its original healthy function, depending on the sitveery of the initial wound and on the function itself. But because the skin does not fully rovceer, scarring continues to be a major clinical issue for doctors around the world. And even though researchers have made significant strides in understanding the heilnag process, many fnenudaatml mysteries remain uelevrnosd. For instance, do fibroblast cells arvrie from the blood vessels or from skin tissue adjacent to the wound? And why do some other mammals, such as deer, heal their wounds much more efficiently and ceoeplmtly than hnumas? By finding the answers to these questions and others, we may one day be able to heal ourselves so well that scars will be just a memory.

Open Cloze

The largest organ in your body isn't your liver or your brain. It's your skin, with a surface area of about 20 square feet in ______. Though different areas of the skin have different characteristics, much of this surface performs similar functions, such as sweating, feeling heat and cold, and growing hair. But after a deep cut or wound, the newly healed skin will look different from the surrounding area, and may not fully regain all its abilities for a while, or at all. To understand why this happens, we need to look at the structure of the human skin. The top _____, called the epidermis, ________ mostly of hardened cells, called keratinocytes, and provides protection. Since its outer layer is constantly being shed and renewed, it's pretty easy to repair. But sometimes a wound penetrates into the dermis, which contains blood vessels and the various ______ and nerve endings that enable the skin's many functions. And when that happens, it ________ the four overlapping stages of the ____________ _______. The first stage, hemostasis, is the skin's response to two immediate threats: that you're now ______ blood and that the physical _______ of the _________ has been compromised. As the blood vessels tighten to minimize the bleeding, in a process known as vasoconstriction, both _______ are averted by forming a blood clot. A special protein known as fibrin forms cross-links on the top of the skin, preventing _____ from flowing out and bacteria or pathogens from getting in. After about three hours of this, the skin begins to turn red, signaling the next _____, inflammation. With bleeding under control and the barrier secured, the body sends _______ cells to fight any pathogens that may have gotten through. Among the most important of these are white blood cells, known as macrophages, which devour bacteria and ______ tissue through a process known as phagocytosis, in addition to producing growth factors to spur healing. And because these tiny soldiers need to ______ through the blood to get to the wound site, the previously constricted blood vessels now expand in a process called ____________. About two to three days after the wound, the proliferative stage ______, when fibroblast cells begin to _____ the wound. In the process of collagen __________, they produce a fibrous protein ______ collagen in the wound site, _______ connective skin tissue to replace the ______ from before. As epidermal cells divide to ______ the _____ layer of skin, the dermis contracts to close the _____. Finally, in the fourth stage of remodeling, the wound _______ as the newly _________ collagen is rearranged and converted into specific types. Through this process, which can take over a year, the tensile strength of the new skin is improved, and blood vessels and other connections are strengthened. With time, the new tissue can reach from 50-80% of some of its original healthy function, depending on the ________ of the initial wound and on the function itself. But because the skin does not fully _______, scarring continues to be a major clinical issue for doctors around the world. And even though researchers have made significant strides in understanding the _______ process, many ___________ mysteries remain __________. For instance, do fibroblast cells ______ from the blood vessels or from skin tissue adjacent to the wound? And why do some other mammals, such as deer, heal their wounds much more efficiently and __________ than ______? By finding the answers to these questions and others, we may one day be able to heal ourselves so well that scars will be just a memory.

Solution

humans
travel
damage
process
stage
glands
forming
wound
matures
healing
barrier
epidermis
blood
occurs
completely
regenerative
threats
severity
triggers
vasodilation
deposition
called
reform
enter
losing
fundamental
adults
deposited
layer
outer
unresolved
arrive
consists
fibrin
special
recover

Original Text

The largest organ in your body isn't your liver or your brain. It's your skin, with a surface area of about 20 square feet in adults. Though different areas of the skin have different characteristics, much of this surface performs similar functions, such as sweating, feeling heat and cold, and growing hair. But after a deep cut or wound, the newly healed skin will look different from the surrounding area, and may not fully regain all its abilities for a while, or at all. To understand why this happens, we need to look 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 being shed and renewed, it's pretty easy to repair. But sometimes a wound penetrates into the dermis, which contains blood vessels and the various glands and nerve endings that enable the skin's many functions. And when that happens, it triggers the four overlapping stages of the regenerative process. The first stage, hemostasis, is the skin's response 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 minimize the bleeding, in a process known as vasoconstriction, both threats are averted by forming a blood clot. A special protein known as fibrin forms cross-links on the top of the skin, preventing blood from flowing out and 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 control and the barrier secured, the body sends special cells to fight any pathogens that may have gotten through. Among the most important of these are white blood cells, known as macrophages, which devour bacteria and damage tissue through a process known as phagocytosis, in addition to producing growth factors to 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 tissue to replace the fibrin from before. As epidermal cells divide to reform the outer layer of skin, the dermis contracts to close the wound. Finally, in the fourth stage of remodeling, the wound matures as the newly deposited collagen is rearranged and converted into specific types. Through this process, which can take over a year, the tensile strength of the new skin is improved, and blood vessels and other connections are strengthened. With time, the new tissue can reach from 50-80% of some of its original healthy function, depending on the severity of the initial wound and on the function itself. But because the skin does not fully recover, scarring continues to be a major clinical issue for doctors around the world. And even though researchers have made significant strides in understanding the healing process, many fundamental mysteries remain unresolved. For instance, do fibroblast cells arrive from the blood vessels or from skin tissue adjacent to the wound? And why do some other mammals, such as deer, heal their wounds much more efficiently and completely than humans? By finding the answers to these questions and others, we may one day be able to heal ourselves so well that scars will be just a memory.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
blood vessels	5
outer layer	2
fibroblast cells	2
skin tissue	2

Important Words

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