Name: 皮膚的科學 (The science of skin - Emma Bryce)
Uploaded: 2018-05-26T21:01:02.000Z
Duration: 5 min 11 s

Between you and the rest of the world  lies an interface

that makes up 16% of your physical weight.

This is your skin, the largest organ  in your body:

laid out flat, it would cover close to  1.7 square meters of ground.

Its purpose may seem obvious— to keep our insides in.

皮膚的作用很簡單，保護體內器官

reveals that it plays a surprising  number of roles in our lives.

皮膚在我們生活中扮演很驚人的角色

Skin is the foundation  of the integumentary system,

which also incorporates your hair,  nails, and specialized glands and nerves.

連接毛髮、指甲、特殊腺體和神經細胞

skin's thickness varies  from 0.5 millimeters at its thinnest

皮膚厚度因部位而異，最薄是 0.5 公釐

and up to four millimeters  at its thickest.

On a daily basis, its huge surface  processes hundreds, if not thousands,

每天皮膚的廣闊表面進行著千百個

relying mostly on large,  pressure-sensitive skin components

完全仰賴龐大、壓力感知的皮膚構造

there are 750 Merkel cells  per each square-centimeter of skin,

皮膚每 1 平方公分就有 750 個梅克爾細胞

coupled with over 2,500 receptors that give you your sense of touch.

內含 2,500 個感知細胞，賦予我們觸覺

This surface is also the body's first  major line of defense.

Without it, you'd be a soggy mass  of tissue and fluids,

若沒有皮膚，你會變成一攤摻和組織細胞的水

with flexible collagen  that makes up most of its dermal layer.

具彈性的膠原蛋白佈滿在真皮層

The epidermis is made up mainly  of skin cells called keratinocytes

that are completely replaced  every four weeks.

As new cells form at the base of the epidermis, older ones are pushed up.

新的細胞在表皮層生成的同時，老舊細胞會被往上推

they're filled with a hardened protein  called keratin.

稱為角質的硬化蛋白質會覆蓋這些細胞

they form a tightly-overlapping,  waterproof layer

that's difficult for invading  microbes to breach.

Any harmful microbes that make it  into the epidermis

This group of protective skin cells  detects invaders

這類型的防禦皮膚細胞會偵測外在威脅

and communicates their presence  to resident immune system T-cells,

並且會發出訊號呼叫免疫系統 T 細胞取代自己

which react by launching  an immune response.

is the several thousand  species of microorganisms

These microbes,  which include bacteria and fungi,

an oily substance that's secreted  onto the skin's surface

by sebaceous glands nestled inside the dermis.

These skin microbes keep the immune system in a state of constant surveillance,

這些皮膚微生物讓免疫系統維持長期的備戰狀態

ensuring that it's ready to react  if the body really is at risk.

確保身體承受風險時，免疫系統能夠馬上進行反應

your skin is also a sensory organ that helps regulate your body's temperature,

皮膚同時是感應器官，能夠調節體溫

Nerves detect whether your skin  is warm or cold

and communicate that information to your brain.

In return, the brain instructs localized blood vessels

to either expand if the body is too warm,

releasing heat from  the blood through the skin,

or to constrict if the body is cold, which retains heat.

若體溫低，則收縮血管保持溫度

At any given time, up to 25% of the body's blood is circulating through the dermis,

任何時候，人體有 25% 的血液流經真皮層

the skin's sweat glands will secrete sweat via ducts onto the surface,

皮膚的汗腺會透過管路分泌汗水至皮膚表面

Hair can also be stimulated to conserve or release body warmth.

The average human  has 5 million hair follicles

except the palms of your hands  and soles of your feet.

Ninety to 150,000 of those  are on your scalp,

where they help shield the large surface area of your head

When you're cold, tiny muscles  called arrector pilli

感到寒冷時，稱為「豎毛肌」的微小肌肉

cause hair to stand upright across the body.

That's the phenomenon known as goosebumps and it traps body heat close to your skin.

這就是所謂的雞皮疙瘩，將體溫保留在皮膚表面

皮膚廣大的面積不僅具有防護作用

it also enables us to interact  and connect with the world.

也讓我們能夠與外在世界連結或互動

Its multifunctional layer cools us down and keeps us warm.

多功能的皮膚層能夠使身體降溫或升溫

The integumentary system  may be many things,

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皮膚的科學 (The science of skin - Emma Bryce)

crucial

phenomenon

immune

reveal