How a wound heals itself - Sarthak Sinha

傷口如何癒合 — 沙塔克·辛哈 (Sarthak Sinha)

譯者: Regina Chu 審譯者: Geoff Chen

The largest organ in your body isn't your liver or your brain.

身體最大的器官既不是肝也不是腦

It's your skin, with a surface area of about 20 square feet in adults.

而是你的皮膚，成人的皮膚 表面積可達 1.85 平方公尺

Though different areas of the skin have different characteristics,

雖然不同部位的皮膚有不同的特性

much of this surface performs similar functions,

這整塊表面的功能大致類似

such as sweating, feeling heat and cold, and growing hair.

譬如排汗、感覺冷熱及生長毛髮

But after a deep cut or wound,

但在很深的割傷或創傷之後

the newly healed skin will look different from the surrounding area,

新癒合的皮膚與其周圍 看起來很不一樣

and may not fully regain all its abilities for a while, or at all.

並很可能暫時無法恢復 甚至會完全失去其功能

To understand why this happens, we need to look at the structure of the human skin.

要瞭解為什麼會這樣 我們必須看一下人類皮膚的結構

The top layer, called the epidermis,

最上面這一層稱為表皮

consists mostly of hardened cells, called keratinocytes,

主要由硬化的細胞 稱角質細胞組成

and provides protection.

並提供保護

Since its outer layer is constantly being shed and renewed,

由於其最外層會一直脫落並再生

it's pretty easy to repair.

所以很容易修護

But sometimes a wound penetrates into the dermis,

但有時候創傷穿透至真皮

which contains blood vessels and the various glands and nerve endings

其包含血管、各種腺體及神經末端

that enable the skin's many functions.

賦予皮膚許多功用

And when that happens, it triggers the four overlapping stages

在這種情況下 皮膚會啟動四個部分重疊的

of the regenerative process.

再生過程階段

The first stage, hemostasis, is the skin's response to two immediate threats:

第一個階段為止血 是皮膚對兩種直接威脅的反應

that you're now losing blood

即你正在失血

and that the physical barrier of the epidermis has been compromised.

及表皮的物理屏障受到損害

As the blood vessels tighten to minimize the bleeding,

此時血管緊繃以減少出血

in a process known as vasoconstriction,

這個過程稱為血管收縮

both threats are averted by forming a blood clot.

血栓形成以避免這兩種威脅

A special protein known as fibrin forms cross-links on the top of the skin,

一種稱為纖維蛋白的特殊蛋白質 在皮膚最上層形成交叉連結

preventing blood from flowing out and bacteria or pathogens from getting in.

防止血液流出 及細菌或病原體進入

After about three hours of this, the skin begins to turn red,

大約三個小時後皮膚開始轉紅

signaling the next stage, inflammation.

表示下個階段開始，發炎

With bleeding under control and the barrier secured,

現在出血已經受到控制 屏障也築好了

the body sends special cells to fight any pathogens that may have gotten through.

身體開始送特化的細胞 對抗任何可能入侵的病原體

Among the most important of these are white blood cells,

其中最重要的是白血球細胞

known as macrophages,

一般稱為巨噬細胞

which devour bacteria and damage tissue through a process known as phagocytosis,

它吞噬細菌及受損的組織 這個過程稱吞噬作用

in addition to producing growth factors to spur healing.

之外還產生生長因子以增進癒合

And because these tiny soldiers need to travel

因為這些微小的軍人

through the blood to get to the wound site,

需要透過血液移動到受傷的地方

the previously constricted blood vessels now expand

原本緊縮的血管現在擴張

in a process called vasodilation.

這個過程稱為血管舒張

About two to three days after the wound,

在受傷後二至三天

the proliferative stage occurs, when fibroblast cells begin to enter the wound.

增生階段發生 此時纖維母細胞開始進入創傷處

In the process of collagen deposition,

在膠原蛋白沉積過程中

they produce a fibrous protein called collagen in the wound site,

它們在創傷處產生一種 纖維性蛋白質稱作膠原蛋白

forming connective skin tissue to replace the fibrin from before.

形成皮膚結締組織 以取代原先的纖維蛋白

As epidermal cells divide to reform the outer layer of skin,

表皮細胞分裂 再生皮膚外層的同時

the dermis contracts to close the wound.

真皮就收縮使創傷收口

Finally, in the fourth stage of remodeling,

最後，在第四個階段「重塑」過程中

the wound matures as the newly deposited collagen is rearranged and converted

隨著新沉積的膠原蛋白排列完成 及轉變成特殊型態

into specific types.

創傷逐漸成熟定型

Through this process, which can take over a year,

這個過程可花超過一年的時間

the tensile strength of the new skin is improved,

在這過程中新皮的抗拉強度會增加

and blood vessels and other connections are strengthened.

血管及其他連結也會增強

With time, the new tissue can reach from 50-80%

隨著時間，新組織會恢復五到八成

of some of its original healthy function,

其原有的健康功能

depending on the severity of the initial wound and on the function itself.

程度取決於最初創傷的嚴重性 及其原本的功能是什麼

But because the skin does not fully recover,

但是由於皮膚不可能完全恢復原狀

scarring continues to be a major clinical issue for doctors around the world.

疤痕處理一直都是全世界醫師 主要的臨床問題

And even though researchers have made significant strides

即使研究人員對瞭解傷口癒合過程

in understanding the healing process,

已有明顯的進步

many fundamental mysteries remain unresolved.

許多基本的謎團仍未解決

For instance, do fibroblast cells arrive from the blood vessels

例如，纖維母細胞是由血管

or from skin tissue adjacent to the wound?

還是由傷口鄰近的皮膚組織送達？

And why do some other mammals, such as deer,

為什麼有些哺乳類例如鹿

heal their wounds much more efficiently and completely than humans?

傷口癒合程度比人類又快又好？

By finding the answers to these questions and others,

藉由找到這些問題 及其他的問題的解答

we may one day be able to heal ourselves so well that scars will be just a memory.

我們有一天或許能完全療傷 疤痕僅成記憶