Tattoos have often been presented in popular media as either marks of the dangerous and deviant or trendy youth fads. But while tattoo styles come and go, and their meaning has differed greatly across cultures, the practice is as old as civilization itself. Decorative skin markings have been discovered in human remains all over the world, with the oldest found on a Peruvian mummy dating back to 6,000 BCE. But have you ever wondered how tattooing really works? You may know that we shed our skin, losing about 30-40,000 skin cells per hour. That's about 1,000,000 per day. So, how come the tattoo doesn't gradually flake off along with them? The simple answer is that tattooing involves getting pigment deeper into the skin than the outermost layer that gets shed. Throughout history, different cultures have used various methods to accomplish this. But the first modern tattooing machine was modeled after Thomas Edison's engraving machine and ran on electricity. Tattooing machines used today insert tiny needles, loaded with dye, into the skin at a frequency of 50 to 3,000 times per minute. The needles punch through the epidermis, allowing ink to seep deep into the dermis, which is composed of collagen fibers, nerves, glands, blood vessels and more. Every time a needle penetrates, it causes a wound that alerts the body to begin the inflammatory process, calling immune system cells to the wound site to begin repairing the skin. And it is this very process that makes tattoos permanent. First, specialized cells called macrophages eat the invading material in an attempt to clean up the inflammatory mess. As these cells travel through the lymphatic system, some of them are carried back with a belly full of dye into the lymph nodes while others remain in the dermis. With no way to dispose of the pigment, the dyes inside them remain visible through the skin. Some of the ink particles are also suspended in the gel-like matrix of the dermis, while others are engulfed by dermal cells called fibroblasts. Initially, ink is deposited into the epidermis as well, but as the skin heals, the damaged epidermal cells are shed and replaced by new, dye-free cells with the topmost layer peeling off like a heeling sunburn. Blistering or crusting is not typically seen with professional tattoos and complete epidermal regeneration requires 2-4 weeks, during which excess sun exposure and swimming should be avoided to prevent fading. Dermal cells, however, remain in place until they die. When they do, they are taken up, ink and all, by younger cells nearby, so the ink stays where it is. But with time, tattoos do fade naturally as the body reacts to the alien pigment particles, slowly breaking them down to be carried off by the immune system's macrophages. Ultraviolet radiation can also contribute to this pigment breakdown, though it can be mitigated by the use of sunblock. But since the dermal cells are relatively stable, much of the ink will remain deep in the skin for a person's whole life. But if tattoos are embedded in your skin for life, is there any way to erase them? Technically, yes. Today, a laser is used to penetrate the epidermis and blast apart underlying pigment colors of various wavelengths, black being the easiest to target. The laser beam breaks the ink globules into smaller particles that can then be cleared away by the macrophages. But some color inks are harder to remove than others, and there could be complications. For this reason, removing a tattoo is still more difficult than getting one, but not impossible. So a single tattoo may not truly last forever, but tattoos have been around longer than any existing culture. And their continuing popularity means that the art of tattooing is here to stay.
大眾媒體經常介紹刺青 像是危險和另類的標誌 或是時髦的年輕時尚。 但當紋身風格變來變去時, 不同的文化會有著 非常不同的含意 這項民俗和文明社會的歷史一樣悠久 在世界各地,都有發現人類遺骸 皮膚上都有裝飾的圖騰 最早的發現可追溯到 西元前 6000 年的秘魯木乃伊 但你有沒有想過 刺青到底是怎麼刺的? 你應該知道我們的皮膚會脫落 皮膚細胞大概每小時 會死 3 到 4 萬 也就是一天約 1 百萬 那麼為什麼刺青 不會隨著皮膚細胞脫落? 簡單來說,因為刺青的顏料 不是刺在會脫落的皮膚表層 而是刺進皮膚的更深層 縱觀歷史,不同的文化 有很多種不同的刺青方法 第一個現代紋身機器 是以湯瑪士愛迪生的雕刻機為藍本 以電力驅動 現代用的紋身機 細微針頭吸取墨水刺進皮膚 以每分鐘刺 50 到 3000 下的頻率 針頭刺穿皮膚表層 讓墨水滲進真皮層 那是由膠原纖維 神經 分泌腺 血管等組成的 每一次針頭刺下都會造成傷口 讓身體產生發炎反應 免疫系統的細胞開始修復受傷的皮膚 就是這樣的過程 讓紋身永遠留在皮膚上 一開始 一種名叫巨噬細胞的特殊細胞 吃掉入侵物質 企圖消炎 這些細胞遊走淋巴系統 一部分細胞帶著染料進入淋巴結 其他的留在真皮層 這樣顏色就不會跑掉 皮膚上就可看到留下的色素 一些墨水顆粒會懸浮在 真皮的凝膠狀基質 其他的會被名為纖維原細胞的 真皮細胞吞噬 其實,色素也應該沉積在表皮層 但當皮膚癒合 受損的表皮細胞脫落 換成沒有染色的新細胞 脫落後,表皮淺層看起來會像曬傷 專業的刺青比較不會起水泡或結痂 表皮再生過程需要約 2-4 周 期間,避免褪色 不要過度曬太陽或游泳 染色的真皮細胞在死之前都會留著 而死後 周圍的年輕細胞會接收其顏色 所以顏色仍會留下 但紋身仍會隨著時間變淡 身體會對外來的顏料顆粒做出反應 免疫系統的巨噬細胞 會慢慢將顆粒打散帶走 紫外線也會打散顆粒 雖然擦防曬乳就可以避免紫外線 但因真皮細胞相對穩定 大部分一輩子都會留在 較深層的皮膚內 如果紋身一輩子都不會褪 那我們有辦法消除它嗎? 技術上來說, 可以 現今,雷射可以穿透表皮層 並打散不同波長的顏料 黑色最容易消除 激光束破壞帶有色素的細胞 變成較小的顆粒 巨噬細胞會清理帶走這些顆粒 但有些顏色就比較難清除 方法就會複雜一些 所以消除紋身會比刺上身難的多 但也不是不可能消除 所以紋身並非永恆不滅 紋身歷史比任何文化歷史都長 它的普及代表著 刺青藝術已被大眾接受