When it comes to your body, science has figured out how to hack, synthesize, or replace a

當談到你的身體時，科學的發展已經完全知道如何駭進、合成或者置換掉

surprising amount of its parts and processes.

它的很大一部分的組成部件和運作的程序

We have implants to keep heart beats steady, and steel rods to mimic bones.

已經存在可以植入維持心臟平穩跳動的器具和模仿骨頭的鐵棍

We’ve got drugs that can replace hormones, and antibiotics to cover for your immune system,

我們已發明出可以取代賀爾蒙的藥物，以及與免疫系統提供相似功能的抗生素

and pretty soon you’ll be able to just 3D print a new ear if you need one. Really!

而很快地如果你需要的話，就能夠用3D列印的方式做出一隻新的耳朵。千真萬確！

But one thing we absolutely cannot manufacture -- despite what True Blood would have you believe --

但有個東西我們絕對無法製造 -- 儘管電影噬血真愛使你以為可以 --

is blood. And yet blood is a thing that we all need.

那就是血液。而血液是我們最需要的東西之一

And sometimes, because of injury or illness, we need extra blood.

而有時候，由於病痛或受傷，我們會需要額外血液的補充以維持生命

In fact, every two seconds, someone in the U.S. needs a blood transfusion. This could

事實上，在美國每兩秒鐘就有一人需要輸血。這個人也許

be a victim of a car accident, someone undergoing surgery, or a cancer patient who needs new

是車禍的受害者、某個正在動手術的人或者癌症病患

blood to maintain their health during chemotherapy.

必須靠輸血以在化療過程中維持健康

And because we can’t grow it on trees, or make it in a lab, or even it store it for

而因為我們無法從樹上長出血液或者在實驗室合成出來或者甚至長時間地

all that long, the blood that people need -- nearly 16 million pints a year in the U.S.

保存它，以提供需要的人們使用 -- 美國一年需要將近1,600萬品脫的血量

-- has to come from people who have donated it.

-- 需要由人們來捐贈以滿足需求

So let’s talk blood, shall we?

所以我們來談談血液，好嗎？

The meal of choice for vampires and female mosquitoes, blood is red, sticky, salty, and

吸血鬼和母蚊子的大餐，血是紅色、黏稠、鹹且

kind of metallic tasting.

嚐起來帶有金屬味

It is indeed thicker than water, and super viscous -- which is why Hitchcock used chocolate

血液的確比水要濃厚，且超級黏稠 -- 這也就是為什麼希區考克會用巧克力

syrup as a stand-in in a certain classic shower scene.

糖漿當做某些經典淋浴場景的替代品

For most purposes, blood comes in eight different types, and it accounts for about 8% of your body weight.

對大多數的目的，血液有八種不同的類型，且佔你身體約百分之八的重量

You might remember from our episodes on tissues that blood is a type of connective tissue,

你可能記得我們談論組織的章節中提到血液是一種連結組織

which means it’s made of living cells suspended in a nonliving matrix, which in this case

也就是說它是由懸浮在不具有生命的液體中的活生生細胞所組成，在這個例子中就是

is the fluid ground substance called plasma.

一種基本的液體叫做血漿

And of course one of blood’s main missions is to transport and distribute oxygen, nutrients,

而理所當然血液其中一個主要的任務就是將氧氣、養分

waste products, and hormones around the body.

廢物和賀爾蒙運送並分配到身體各處

But it also helps regulate and maintain body temperature, pH levels, and the volume of

但它也幫助調節和維持身體的溫度、酸鹼值和身體中

fluids in your body. Plus it protects you from infection and from the loss of blood itself.

流體的總量。它也保護你免於感染以及在流失血液時能回補

Perhaps second only to your brain, your blood is the one component of your body that we

也許僅次於你的大腦，你的血液是你身體組成的部份當中

haven’t figured out how to reproduce, synthesize, or imitate.

我們尚未清楚了解如何去複製、合成或者模仿的

It’s a part of you that is literally irreplaceable.

真的是完全沒辦法人工取代的一個部分

It’s Saturday and you feel like doing a good deed, so you head over to your local

這就像是到了星期六，你感覺想要做件善事，就到當地的

Red Cross for a blood drive.

紅十字會找了台捐血車

You get your finger pricked and then somebody directs you toward a lounge chair, swabs your

你的手指被刺了一針然後某個人指引你去到一張躺椅上，在你手肘

inner elbow with alcohol, and then comes at you with a hollow needle.

內部擦拭酒精，然後將空心的針頭插入血管中

Once the bag is full -- they usually take about a pint -- you get unhooked and grab

等到血袋滿了之後 -- 通常他們會取約一品脫的量 -- 就會把管子移除然後你就能夠拿

a cookie and a juice to replace the blood sugar you lost. And the whole process takes around 20 minutes.

一塊餅乾和一瓶果汁以補充你所失去的血糖。而這整個過程花費約20分鐘

But for your blood, the day is just beginning. Soon it will be taken to a lab, where it’ll

但是對你捐出去的血液來說只是個開始。很快地，它就會被帶去實驗室裡，在那兒

be tested for infectious diseases and separated into different parts before heading out to hospitals.

血液會受到疾病感染測試以及在被運送往醫院前先做層析分離。

So, hold up: What exactly do I mean by different parts?

所以，等等：我說的分離是什麼意思？

Well, the blood that flows from your arm into that bag is whole blood, a mixture of cells

這個嘛，從你手臂取出注入袋中的血液是全血，也就是混和了細胞

and cell fragments called formed elements, along with water, and lots of dissolved molecules.

和細胞碎片，稱之為組成元素，與水份，還有很多溶解在其中的分子

A patient who needs a transfusion may only need some of those things and not others,

一個需要輸血的病患可能只需要這其中的一些東西而已

so the parts are separated.

所以要把它分層分類開來

Once your blood makes it to a lab, technicians put it in a centrifuge, which spins it around

一旦你的血液到達了實驗室，實驗室操作員就會將其放入離心機，旋轉快到

fast enough to send the heavier components to the bottom of the tubes, and bring the

足以將其中較重的物質留在試管的底層，將較輕的物質

less dense elements to the top.

留在上層

In the centrifuge, three distinct layers emerge.

在離心機中，三個主要的層次會被分出來

Down at the bottom you’ve got a heavy red layer of erythrocytes, or red blood cells

最底層的是重的紅色層稱為erythrocytes。或稱紅血球細胞

that carry oxygen and carbon dioxide. They make up about 45 percent of your total blood volume.

攜帶著氧氣和二氧化碳。它們約佔血液總量的百分之四十五

Then you’ve got this thin little whitish layer in the middle. Those are your warriors,

然後你會看見中間有薄薄一層白色的液體。這些是你血液中的戰士

the leukocytes or white blood cells, that defend your body from toxins and foreign microbes.

為leukocytes或稱白血球細胞，它們的任務是抵禦外來微生物和毒素入侵你的身體

And there are also the cell fragments, called platelets, which help with blood clotting

而還有細胞片段叫做血小板，幫助凝血的機制

and make up less than one percent of your blood.

約佔不到血液的百分之一

Finally, up at the top you see the yellowish plasma, which accounts for about 55%of your blood volume.

最後最上層你會看到黃色的血漿，約佔血液總量的百分之五十五

Plasma is actually 90 percent water, but the other 10 percent is chock full of 100 different

血漿百分之九十是水，其他的百分之十是一百種

solutes, including proteins, electrolytes, gases, hormones, and waste products.

不同的溶質組成，包括蛋白質、電解質、氣體、賀爾蒙和廢物

The most of abundant of these solutes are electrolytes -- which you may have heard of

最豐富的溶質是電解質 -- 你可能有聽過

as the secret ingredient in sports drinks. But they’re really just positively-charged cations -- like calcium,

這是運動飲料中的秘密成分。但他們的確只是帶正電的離子像是鈣離子

sodium, and potassium -- and negatively-charged anions, like phosphate, sulfate, and bicarbonate.

鈉離子和鉀離子 -- 和帶負電的離子，像是氯離子、硫離子和重碳酸鹽類

Together these ions help regulate your blood’s chemistry, maintaining its pH levels and proper osmotic

這些離子聚集起來調節你血液的化學平衡，維持其酸鹼值和適當的滲透壓

pressure, and allowing other tissues to do their jobs, like making muscles contract and sending action potentials.

且使其他組織正常運作，像是讓肌肉收縮和傳遞動作電位

But when measured by weight, the bulk of the solutes in your blood are really the plasma proteins.

但當以重量計算，在你血液中的一大堆溶質裡最多的其實是血漿蛋白質

Most of these proteins -- like albumin, and alpha and beta globulins -- are made by the

這些蛋白質中大多數 --像是白蛋白和alpha及beta球蛋白 --都是由

liver, and do things like balance the osmotic pressure between the blood and surrounding

肝臟製造出來的，而且提供像是血液和周圍組織滲透壓力平衡

tissues, and transport lipids and ions.

以及傳遞離子和油脂

Others run defense for you, like the gamma globulin antibodies that are released by plasma cells during

其他的則擔任你身體的守衛，像是在免疫反應中由血漿細胞釋出的gamma球蛋白抗體

an immune response, or fibrinogen proteins, which are vital to forming blood clots and stopping bleeding.

或者是纖維蛋白原蛋白質，是凝血和形成血栓的重要物質

All right, bleeding. I want to talk about that.

好吧，流血。我想談談這個

Because, for the very reason that I mentioned at the beginning -- that we can’t replace

因為，正如我在一開始所提到的 -- 我們無法用

your blood with some synthetic wonder-fluid -- the LAST THING that your circulatory system

一些合成的神奇液體來取代你的血液 -- 你的循環系統

wants is for you to fritter away your blood, in some sidewalk scrape or kitchen accident.

最不希望的是浪費你寶貴的血液，像是在街頭搏鬥或廚房的意外中受傷

So, it has a whole system in place to prevent you from losing too much of it, through a

所以，有一個完整的系統來阻止你大量的流失血液，從一個

process known as hemostasis.

被稱作止血的機制

So imagine you’re slicing a nice garlic-cheese bagel one morning, and you lacerate the distal

想像你在某個早晨中正在切一片美味的蒜味起司貝果，而你劃破了你的

phalanx of your pollex -- in other words, you cut the tip of your thumb.

拇指末端 -- 換句話說，你割到了你拇指的尖端

And now you’re bleeding all over your breakfast.

且現在你的血留得你的早餐上都是

At the very first sign of a rupture, the blood vessel actually constricts itself, to slow

在血管突然破裂的第一個徵兆出現時，血管中的血流會自我調節而降低

the flow of blood through it.

讓通過這個傷口的血流量減少

Then little cell fragments called platelets gather at the site of the injury, creating

然後被稱之為血小板的小片段細胞就會在傷口處聚集，形成

a plug that dams the breech and keeps the blood from leaking further.

一個栓子堵住且讓血液不再加劇流出

Now these free-floating platelets don’t clump together during regular circulation -- that

這些自由漂流的血小板在正常體循環的狀態下並不會堆積凝結 -- 如果

would be terrible -- but when the endothelial cells lining a blood vessel wall tear, the

會的話就太可怕了 -- 但當內皮細胞填補受傷處將血管壁修復，在下方的

underlying collagen fibers are suddenly exposed. And they chemically react with the platelets,

膠原蛋白纖維突然地出現。且它們與血小板起化學反應

turning them all sticky and glue-like at the scene of the injury.

變得黏黏的且像膠狀物地呈現在傷口處

But that platelet plug still isn’t as strong as it could be -- it needs reinforcement to

但是血小板栓在此時仍不夠牢固 -- 需要經過強化

complete the clotting process.

過程來完成凝血的過程

This reinforcement comes in the form of fibrin threads, protein strands that join together

藉由形成纖維蛋白絲來強化，也就是蛋白質糾纏在一塊兒

to make a sort of mesh that traps the platelets and blood cells.

變成像是一種成團攔阻的障礙物來綁住血小板和紅血球細胞

Eventually, the threads actually pull the opposite sides of the wound together, to close

最終，這些絲線會把傷口兩端收緊縫合上，來關閉

the vessel wall, so the endothelial cells can be replaced.

血管壁，讓內皮細胞能夠來取代接手

Over a few days, the blood vessel heals, and the blood clot dissolves.

過沒幾天，血管壁就會癒合，且血栓就會溶解消失

Or at least, that’s how it is supposed to happen.

或至少，這是該要發生的

People who suffer from disorders related to hemostasis may have trouble with unwanted

人們會遭受與凝血相關異常的痛苦也許肇因於

clotting, or the inability to form clots.

不正常的血栓，或者是無法形成血栓的狀況

In the family of disorders known as hemophilia, a patient can usually complete the first two

在有血友病史的家族中，一名病患通常能完成凝血過程中

steps of hemostasis just fine, but they can’t make an effective fibrin clot. So it’s not that they

的頭兩個步驟，但他們沒辦法製造一個能夠正常運作的纖維蛋白血栓。所以不是因為他們

bleed more than anyone else, it’s just that they bleed longer. Which, I guess means that they bleed more.

比別人流血流得多，只是因為他們流血的時間持續比較久。也就是我猜測導致他們流比較多血的原因

As a result, they may need frequent blood transfusions throughout their lifetime.

結果就是，他們可能在一生當中會常常需要輸血

Which brings me right back around to that Saturday morning blood drive.

也讓我回想起星期六早晨的捐血車

Another thing you’re going to need to know before you give blood is what type you have

另一件事情你需要在捐血之前知道的是自己的血型

-- do you have A, B, AB, or O?

-- 你是A、B、AB或O型血？

These different types all do the job equally well, they just sort of have a different flavor

這些不同的血型都能夠達到相同的目的，只是你的免疫系統有些

related to your immune system.

不同的特定偏好

All the cells in your body have a plasma membrane with specialized glycoprotein markers on them

在你身體中的全部細胞都具有特化糖蛋白標記的血漿膜在上面

that act like name tags or labels, sort of like “This cell is Property of Hank.”

執行像是標記或標籤的功能，有點像是『這個細胞是漢克的財產』

These markers are your antigens.

這些標記物是你的抗原

And your body’s immune system is totally fine with your particular antigens, but if

你帶有特定抗原的身體上的免疫系統在平時是穩定存在的，但一旦

it detects antigens from someone else’s cells -- including viruses or bacteria -- then

他偵測到某個人的細胞上的抗原時 -- 包括病毒或細菌 -- 之後

it’ll send out antibodies to bind to those markers, often to tag them for destruction by the immune system.

它就會送出抗體去與這些標記物相結合，經常是標定以讓免疫系統好辨識並消滅它們

Your red blood cells have specialized antigens on them, called agglutinogens, that activate antibodies

你的紅血球細胞有特化的抗原在上面，叫做凝集原，能活化抗體

that work by binding invading cells to each other, which causes coagulation, or the clumping of blood.

藉由與入侵身體的細胞結合，致使其凝結，或者血液的聚集

Which agglutinogens you have on your erythrocytes defines your blood type.

你有哪種凝集原在你的紅血球細胞上面就會決定你的血型

But they’re classified in two different ways.

但是血液被兩種不同的類型方式分類

In the most important blood classification -- the kind people are most familiar with

最重要的一種分類法 -- 也是人們最為熟悉的

-- there are only two kind of agglutinogens, simply A and B. And your blood can either have

-- 就是只有兩種的凝集原，就是A和B。而你的血液中能夠具有

one, or both, or neither of these molecules.

不是這些分子當中的其中一種，或者兩種都有，又或者兩者都沒有

So the name of your blood type refers to what kind you have or don’t have: A-type has

所以你血型的名字可以推論你有或者沒有哪種凝集原 ：A型有

A antigens, B-type has B, AB has both, and O has neither.

A抗原，B型有B抗原，AB兩者都有，而O兩者都沒有

So, why do you need to know what type you are before you give or receive blood?

所以，你為什麼需要在捐血或者受血之前就知道自己的血型？

Well, like I mentioned: If you have either of these antigens, your body will be fine

這個嘛，正如我所說：如果你兩種抗原都沒有，你的身體就會

with it, because it doesn’t produce any antibodies that label it for attack.

適應的很好，因為不會有任何抗體被標記上要去攻擊的記號

So if you don’t have a particular antigen on your blood cells -- say the type B -- then

所以你的血球上若沒有特定一種抗原 -- 假設是B型好了 -- 那麼

you do have antibodies that are going to label those B antigens for attack, should they enter your space.

一旦它們進入你的身體系統中，你就會有抗體標記在血球上以致遭受攻擊

So AB-type folks are called universal recipients, because they have both antigens, and therefore

所以AB型的朋友們被稱為萬能受血者，因為他們這兩種抗原具備，所以

no antibodies for either. So they can accept A, or B, or AB, or O blood. Meanwhile, O-type

血液中兩種抗體都沒有。所以他們能夠接受A或B或者AB或者O型的血液。與此同時，O型血

doesn’t have A or B antigens, so those folks have antibodies for both. That means that they

並沒有A或B的抗原，所以他們同時有兩種抗體在血液中。這代表他們

can only accept other O blood.

就只能接受O型血液

And yet that lack of antigens means that Type O blood can mix with other types of blood

但是缺乏抗原的意思是O型血液可以混雜在其他的血型當中

without getting attacked, which is why it’s known as the universal donor.

而不被攻擊，也就是其被稱為萬能捐血者的原因

But just to complicate things a little bit more, you’ve got a whole other set of antigens

但讓事情變得更複雜難懂一點，你的血液在一個完全不同的檢視規範中

with totally different protocol. These are your Rhesus, or Rh antigens, named after the

帶有有其他完整的抗原。那個規範叫做恆河猴血液分類法，或Rh抗原，是以

species of monkey they were first identified in.

最初被發現帶有這種血型的猴子所命名的

Much like A and B, you either have the Rh antigens, in which case you’re Rh positive,

有點像是A和B型血，你血液中不是具有Rh抗原，也就是Rh 陽性

or your don’t, and are Rh negative.

就是沒有，為Rh 陰性

Most of the population is Rh positive, so they don’t have the anti-Rh antibodies,

大多數人都是Rh 陽性，所以他們血液中沒有Rh抗體

which means they can accept either positive or negative blood. But negative types should

也就是說他們可以接受陽性或陰性血液。但是陰性的

stick to just the Rh negative blood.

就只能接受Rh陰性血

And since the presence of A-B antigens is controlled by different genes than the Rh

而自從A-B抗原的表現與否被不同基因所控制，而Rh表現與否

ones, we end up with eight different blood types -- four separate groups, each with two variations.

由其他基因控制，所以我們最後擁有吧種不同血液類型 -- 四個不同的群組，每個群組有兩個變數

And now, hopefully, you understand why it’s so hard to replace blood, and why True Blood

現在，幸運的是，你了解為什麼取代血液如此困難了吧，而為什麼噬血真愛

is...not true. I’ve not actually ever seen that show.

並不是....真的了吧。我其實根本沒看過那部片

Along the way, you also learned the basic components of blood -- including erythrocytes,

一路走來，你也學到了血液的基本組成 -- 包括了紅血球

leukocytes, platelets, and plasma -- as well as the basic process of hemostasis that stops

白血球，血小板和血漿 -- 也學了基本的止血機制

bleeding, and how antigens are responsible for the blood type that you have.

且了解抗原是如何對你的血液類型做出反應的

Thanks to all of our Patreon patrons who make Crash Course possible through their monthly

感謝所有在Patreon上的贊助者每個月的貢獻，讓Crash Course 能繼續下去

contributions. If you like Crash Course and want to help us keep making it for free for

你若喜愛Crash Course且想要盡一份心力讓它繼續對

everyone in the world, you can go to patreon.com/crashcourse

全世界每個人都是免費使用的話，請上patreon.com/crashcourse

Also, a big thank you to Bryan Drexler for co-sponsoring this episode.

同時，對Bryan Drexler，我們這集的共同贊助者至上最高謝意

Crash Course Anatomy and Physiology is filmed in the Doctor Cheryl C. Kinney Crash Course

Crash Course解剖學和生理學是在Doctor Cheryl C. Kinney Crash Course

Studio. This episode was written by Kathleen Yale, the script was edited by Blake de Pastino,

Studio拍攝的。這集劇本由Kathleen Yale撰寫，由Blake de Pasitno編輯

and our consultant, is Dr. Brandon Jackson. It was directed and edited by Nicole Sweeney,

而我們的顧問是Dr. Brandon Jackson。由Nicole Sweeney 指導和編輯

the sound design was by Michael Aranda, and our graphics team is Thought Cafe.

音效由Michael Aranda負責，而動畫團隊是Thought Cafe