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皮肤的科学

The science of skin - Emma Bryce

The finest clothing made is a person’s own skin, but, of course, society demands something more than this.
皮肤是人类最精美的服饰 然而社会所需要的东西却远不止这些
——马克·吐温
Between you and the rest of the world lies an interface
在你和外界之间存在着一个界面
that makes up 16% of your physical weight.
它占据了你体重的16%
This is your skin, the largest organ in your body:
它就是你的皮肤 是你身体最大的器官
laid out flat, it would cover close to 1.7 square meters of ground.
如果把它平铺开来 它会覆盖将近1.7平方米的地表
Its purpose may seem obvious— to keep our insides in.
皮肤用途很明显——保护我们的身体内部
But a look beyond the surface
但透过对表皮的观察
reveals that it plays a surprising number of roles in our lives.
揭示了它在我们的生活中扮演的许多令人惊讶的角色
First, the basics.
首先 基础功能
Skin is the foundation of the integumentary system,
皮肤是表皮系统的基础
which also incorporates your hair, nails, and specialized glands and nerves.
它还包括你的头发 指甲 专门的腺体和神经
Made up of three layers, the epidermis, dermis,
皮肤是由 表皮层 真皮层
and hypodermis, skin ’ s thickness
和下皮层 这三层构成的 皮肤的厚度范围
varies from 0.5 millimeters at its thinnest
可从最薄的0.5毫米
and up to four millimeters at its thickest.
到最厚的4毫米
It also carries out three key functions: protecting,
它还具有三种主要功能
regulating, and sensing the world beyond its limits.
保护 调节以及感知外界
On a daily basis,
在日常基础之上
its huge surface processes hundreds, if not thousands,
它庞大的表面处理着成百上千种
of physical sensations,
身体的感觉
relying mostly on large, pressure-sensitive skin components
这很大程度上依赖于 被称为默克尔细胞
called Merkel cells.
皮肤压迫敏感度
In your fingertips alone,
单单在你指尖上
there are 750 Merkel cells per each square-centimeter of skin,
每平方厘米的皮肤就分布着750个默克尔细胞
coupled with over 2,500 receptors that give you your sense of touch.
配合着给你触感的2500个神经末梢
This surface is also the body’s first major line of defense.
皮肤还是人体的第一道防线
Without it, you’d be a soggy mass of tissue and fluids,
没有它 你就会变成一堆黏糊糊的组织和液体
fatally exposed to the elements.
最终暴露在大自然当中
Skin effectively seals off your insides
皮肤有效地封锁了你的身体内部
and also absorbs pressure and shock
由胶原蛋白组成的真皮层还会
with flexible collagen that makes up most of its dermal layer.
来吸收外界的挤压和撞击
The epidermis is made up mainly of skin cells called keratinocytes
主要由皮肤细胞组成的表皮叫做角质细胞层
that are completely replaced every four weeks.
每四周就会完全更新一次
As new cells form at the base of the epidermis,
作为表皮细胞的基础的新的细胞形式
older ones are pushed up.
老化细胞将会被代谢到体表
When these cells move upwards,
当这些细胞向上移动时
they’re filled with a hardened protein called keratin.
会充满了一种硬化的叫做角蛋白的东西
Once they reach the surface, they form a tightly-overlapping, waterproof layer
一旦它们到达体表 就会排列成紧密重叠的防水层
that’s difficult for invading microbes to breach.
细菌就很难对皮肤进行入侵破坏
Any harmful microbes that make it into the epidermis
任何抵达表皮的有害细菌
will encounter Langerhans cells.
都将会遇到朗格汉斯细胞
This group of protective skin cells detects invaders
这组保护皮肤的的细胞能抵挡细菌入侵
and communicates their presence to resident immune system T-cells,
并将它们的存在传递给免疫系统
which react by launching an immune response.
它们通过启动免疫来做出回应
A crucial feature of this immune defense
而这种免疫抵抗的关键特性在于
is the several thousand species of microorganisms
寄宿在表皮和你皮肤缝隙中的
that inhabit the planes, folds, and crevices of your skin.
成百上千种的微生物
These microbes, which include bacteria and fungi,
这些微生物包括活跃在皮脂下的
thrive in the sebum,
细菌和真菌
an oily substance that ’ s secreted onto the skin ’ s surface
通过分布在真皮下的油脂分泌腺体
by sebaceous glands nestled inside the dermis.
在皮肤的表面分泌油质
These skin microbes keep the immune system
这些皮肤微生物能保证免疫系统
in a state of constant surveillance,
维持持续的活性状态
ensuring that it ’ s ready to react
能够确保当身体处于风险状态下时
if the body really is at risk.
随时做出应对
Beyond this protective role,
除了充当保护的角色之外
your skin is also a sensory organ that
你的皮肤还是能帮助你
helps regulate your body ’ s temperature,
调节体温的感觉器官
two roles that are closely interlinked.
这两个角色有着非常紧密的内在联系
Nerves detect whether your skin is warm or cold
神经检测你的皮肤是冷是热
and communicate that information to your brain.
并把信息传递到你的大脑
In return, the brain instructs localized blood vessels
反过来 你的大脑指挥局部的血管
to either expand if the body is too warm,
当你的体温过高 就会让血管扩展
releasing heat from the blood through the skin,
通过皮肤来释放血液中的热量
or to constrict if the body is cold, which retains heat.
或者是身体过冷的时候收缩血管来保持温度
At any given time,
在任何特定的时间
up to 25 % of the body’s blood is circulating through the dermis,
人体百分之二十五的血液在表皮之下循环流动
making this process extremely efficient.
以确保整个过程的效果
Under warm conditions,
在温暖条件下
the skin ’ s sweat glands
皮肤的汗腺
will secrete sweat via ducts onto the surface,
会在皮肤表面分泌出汗液
transferring heat out of the body.
把体内的热量传递到外界
Hair can also be stimulated to conserve or release body warmth.
汗毛也会在外界刺激之下维持或者是释放身体的热量
The average human has 5 million hair follicles
人类平均有五百万个毛囊
embedded everywhere on the body
分布在除了手掌和脚掌
except the palms of your hands and soles of your feet.
之外的身体各部分
Ninety to 150,000 of those are on your scalp,
而这些毛囊中有九十至十五万个分布在头皮
where they help shield the large surface area of your head
它们能保护你头部绝大部分地方
from physical damage and sunburn.
避免外界的伤害或者是晒伤
When you’re cold, tiny muscles called arrector pilli
当你感觉冷的时候 叫做皮利立肌的微小肌肉
cause hair to stand upright across the body.
会让你身体的毛发直立起来
That ’ s the phenomenon known
这就是被人叫做
as goosebumps and it traps body heat close to your skin.
鸡皮疙瘩的现象 它能保持皮肤的温度
Skin’s vast surface isn’t just a shield;
大部分的皮肤不仅仅只是起防御作用
it also enables us to interact and connect with the world.
它还能帮助我们与外界感知和联系起来
Its multifunctional layer cools us down and keeps us warm.
它具有平衡人体温度的多种功能
The integumentary system may be many things,
表皮系统的确比皮下层
but it’s certainly more than skin deep.
起到更大的效用

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视频概述

你真的了解你的皮肤吗?或许看完本条视频,你会对自己的皮肤有更深刻的认识。

听录译者

收集自网络

翻译译者

Mavy 大可

审核员

审核员 V

视频来源

https://www.youtube.com/watch?v=OxPlCkTKhzY

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