shows you really neatly where the heart sits in our body

体のどこにあるかよく分かります。

so you can see the heart is surrounded, on both sides, by ribs, right?

心臓は肋骨に囲まれています。

And in fact, I didn't draw it in yet, but let me show you where the

そしてその横には肺があります。

lungs would be. This is the right lung

これが右、こちらが左の肺です。

and on this side you'd have the left lung. So this is where

心臓はこのように肺の間にあります。

your heart sits: between two lungs. And I'm saying

左右はこの人から見た右と左です。

left and right from the perspective of the the person who owns this

こちらから見ると反対になります。

heart. So this is their left and right, which is the opposite

このように心臓は肺と肺の間で、肋骨に守られています。

of us if we're looking at it. The heart is actually sitting between the two

その下にはこんな風に、

lungs within this protective casing that

とても大事な筋肉があります。

the ribs are basically there to keep all these important organs

あまり注目されないし、運動するときにも意識されませんが、

safe. And then below them, so if you draw

隔膜といいます。

this here. Or if I draw it, you can

この隔膜と肋骨は1つの部屋を作っていて、

see now that below all this stuff is

隔膜が床に、肋骨が壁と天井にあたります。

a really really important muscle. So this muscle

中には肺と心臓が収まっています。

people don't talk about this muscle, or this is not the kind of muscle

この部分を胸部といいます。

that you usually see people working on at the gym, but this muscle is called the diaphragm.

では心臓はどんな働きをするのでしょう。

So your diaphragm muscle

これは心臓の拡大図です。

and your ribs are enclosing a space, right? The diaphragm becomes the floor, and the ribs are kind of the

これが右の肺、反対側には左の肺があります。

ceiling and the walls of this space.

これが肋骨に囲まれているのですが、割愛します。

And if you look at the contents of this space, you'd have your lung

書き入れると心臓が見えにくいからです。

and you'd have your heart. So, this entire space then

さて、心臓の働きについて考えるとき、細胞を思い浮かべるとわかりやすい。

is called your thorax.

細胞をここに描きましょう。

So what exactly does the heart do? Let's actually make a little bit of

つま先の細胞ということにしましょう。

space now, and bring up a

細胞が生きていくために、この近くには血管があります。

zoomed in version of the heart.

体のどこの細胞でも、近くには血管があります。

Let me start by orienting you to the heart. This is our right lung

このつま先の細胞が生き続けるためには

and on the other side we have our left lung. And all this would be

酸素や、栄養などが必要です。

inside of the rib cage, but I'm not going to draw that now, because that would

細胞が生き続けるには、こういったものが必要です。

make it harder to see the heart itself. So to think

その一方で外に出すものもあります。

about exactly what the heart does, I think one, kind of neat way to do it is

私達の体と同じく、余分なものを排出するのです。

to actually imagine that you're a cell. So put yourself in the perspective

細胞の老廃物といえば二酸化炭素です。

of a cell, and let's say you're a cell hanging out

今、血液が流れていないと仮定します。

over here. This is you. And you can

近くにある血管にも血流はありません。

think about any part of the body that you could be. Let's say a little

つま先の細胞が老廃物を排出すると、

toe cell. So let's say you're a toe cell

こんな風に溜まっていきます。

and your job, of course, is to live and be happy,and you've got

血液が流れていないからです。

near by, a little blood vessel. And in fact, every cell in our body

細胞の周りにも溜まっていきます。

has a little blood vessel that's near by. And this toe cell

そして老廃物で覆われてしまうのです。

is just trying to make a living. And toe

酸素も栄養も運ばれてきません。

cells need certain things, right? They need, for example, let's say oxygen.

一分もすれば、ここは暮らしにくいなと細胞は思うでしょう。

I'll write it in white so it's very clear. They need oxygen

悲しい気持ちになります。

and they need nutrients, right?

こんな状態が続くと細胞は死んでしまいます。

So cells need certain things to live and be happy.

細胞には、足であれ皮膚であれ、どの細胞も

And on the flip-side, they also make waste. They're in

生きている限り、血流が必要です。

a sense just like us, they make waste. And that waste could be

血が流れていれば状況は違います。

all sorts of things, and one that kind of jumps to mind is

このような老廃物は流されていってしまいます。

carbon dioxide (CO2). So carbon dioxide is waste

ゴミが運ばれて、家が綺麗になるようなものです。

for this cell. So it's making some

血液が流れれば、酸素や栄養も運ばれてきます。

waste and for the moment let's imagine that there's no blood flow.

こうして細胞は気分良くなり、健康になるのです。

So, even though there's a blood vessel near by,

体中の細胞をこんな状態にするには

really, no flow is happening, so I'll just write "no flow".

体中の血液がうまく循環している事が大事です。

So as the little cell

これがポイント1。

makes waste. That waste, let's draw a little ball right here,

体中の血液は滞り無く循環していなければなりません。

it's going to start accumulating, you're going to start collecting more and more of it

体中にある何兆個という細胞に血液を循環させるには

since the blood is not really flowing. And it might kind of

強力なポンプが必要です。

end up getting all the way around our toe cell. So our toe cell is getting

血液を吸い込んで、それを吐き出せるようなポンプです。

swamped, literally getting kind of covered by its own waste.

それができるのが心臓であり、心臓の役目なのです。

And on the flip-side, is it getting oxygen or nutrients? No.

血液を体中に送り出して循環させる。

It's not getting either of these things. So, before very

これが心臓の働きの一つめです。

long, I would say within minutes, our toe cell

1つめの働きが血液を送り出すこと。

is thinking, "Well this is not a very happy way to live!" this is

体全体の流れを作り出します。

actually really very sad, this is awful. And if this continues

体中にある細胞に血液を送り出すのです。

the toe cell would die. So, what a toe

どのようにして血液が送り出されるのか、

cell needs, and what every cell needs, and that could be a finger cell or a

この図を見ると分かります。

skin cell, or really any cell that's living, needs

これが静脈です。

flow. Right? It needs this blood to be flowing nicely

こちらが動脈。

and smoothly. And if there is flow

血液は動脈を通ってこちらに流れます。

then you get a very different picture, right? If there's flow then all the sudden all the

こちらの方からは2本の静脈に血液が流れます。

waste product is actually now lifted and taken away.

その内の1本は上大静脈と呼ばれるものです。

It's flowing away, and it's a little bit like having

ここからは見えませんが、

someone come by and pick up the trash, then you don't have trash all over the house.

ここにはもう一本の静脈、下大静脈があります。

So then you have nice flow, and

この2本の静脈が体中の血液を吸い込んで、

in return, oxygen and nutrients are delivered. So this stuff

心臓に送り込んでいるのです。

gets delivered as well. So, all of the sudden the cell is going to be

心臓が拍動によって押し出した血液は動脈に流れます。

very, very happy, and is going to be living just fine.

この動脈を大動脈といいます。

So, really if you want all of the cells in your body to be living just fine

血液はこのようにして心臓の力で循環しているのです。

like this cell here, you really want good flow throughout the

心臓の働きは他にもあります。

body. And so this is really point number one. Is that you really

ふたつ目は肺に血液を送り出すことです。

need, somehow, to have blood flow moving and pushing

肺血流といいます。

blood constantly through the body. So,

細胞は酸素を欲しがっていますね。

to do this for billions and billions of cells you would need a pretty powerful

老廃物も出します。

pump, right? Something that's going to be able to pull

血液の循環は大切なことですが、

in all the blood from the body, and then push it back out. And that's what the heart

循環するだけでは老廃物を除去できず、酸素も供給されません。

is. I mean at its core, that's exactly what the heart is doing.

細胞にとっては住みにくい。

It's an amazing pump, pushing blood, so that

血液の循環と同時に酸素も必要です。二酸化炭素の除去も。

you have good blood flow. And so I'm

ここで肺の登場です。

going to write that on the side as kind of job number one. These are the jobs of the heart.

血液は大動脈に送り出される前に、肺に送られるのです。

So jobs, and number one, would be

左の肺と右の肺に送り込まれ、

blood flow. And I'll write systemic

右と左の肺から血液が戻ってきます。

flow. Systemic flow. And all

そして心臓の収縮によって大動脈に送られるのです。

that systemic means is that I'm refering to the entire body. So systemic

ここで血液はいったん血管を出て肺の中を循環する。

when I say that word, I just mean the entire body. All the cells

これを肺血流といいます。

in the body. Now, exactly how that happens actually

さて、最後にこのグニャグニャ曲がった血管です。

you can see on this picture. So, here you have a giant

心臓全体を覆っています。

vein, this is a vein, and you have an artery.

これは何でしょうか。

This is an artery.

青いのが静脈、赤いのが動脈です。

And blood is actually going through the artery, that way.

これは体全体の循環なのか、肺血流なのか、あるいは別物か。

And it's actually coming into two veins, the one

これらの血管を冠状血管といいます。

at the top, this is called the superior, superior just kind of means

先ほど動脈、静脈という言葉が出てきましたが、

at the top. Superior vena cava. That's the

ここにある血管を総称して冠状血管といいます。

name of the vein. And at the bottom here, you can't see it because

この環状血管は心臓の筋肉に酸素を供給しています。

it's on the other side of the heart, but there's another vein called the inferior vena cava.

心臓は何万個という細胞からできています。

And these two veins, this is also a vein,

この細胞も、つま先の細胞と同様

these two veins are actually dragging blood in from all over the body,

酸素や栄養素を必要とし、老廃物も出します。

into the heart.

ですからそれを供給する血管が必要なのです。

And then, when the heart is ready to pump it back out, it goes into this

これが冠状血管の役目です。

artery, and the name of it is the aorta.

心臓に酸素や栄養素を供給しているのです。

So if you've heard of the aorta, this is the artery that people

心臓の働きを助けているのなら、

are talking about. So this is how blood comes and gets pumped

これは体全体の循環に繋がっているのでしょうか。

around. But this isn't actually the only job of the heart. The job,

肺の血流なのでしょうか。

the second job of the heart, is actually

細胞に酸素を供給するという点からは

also in this picture, and it's called pulmonary flow.

冠状血管は体全体の循環だと言えます。

Pulmonary flow. So, what does that

mean? Well, we know that cells are expecting

oxygen, right? We know this. And that they have a lot of carbon dioxide

waste. Well, it's good to move things around. It's good

to move blood around. But if you actually never got rid of that carbon dioxide

or brought in new oxygen, then a cell is not going to be very happy either.

I mean, you can have blood flow, but at some point it's also going to want some oxygen.

And it's going to want to get rid of that carbon dioxide. So, that's where the

lungs come in. So what happens is that the heart, before

sending blood out the aorta, before just dishing it out back into the body,

it actually sends the blood over to the

lungs. And it goes over to the left lung, and over to the right lung.

And the blood comes back from the right lung

and the left lung, and gets pushed back into

the heart, and then gets squeezed through the aorta. So there's this

actual extra little step here, where blood is going to

and from the lungs, and that's the pulmonary flow.

So the final thing you'll notice, if you look at this picture it's hard not to notice,

is that there are these, kind of wriggly looking little

blood vessels all over the heart. And what are these

exactly? I mean, you've got red ones, and blue ones, and

the blue ones are the veins, and the red ones are the arteries

but are they part of the systemic flow, or pulmonary flow, or something else?

Well, these vessels, all of them,

together are called coronary vessels.

And so specifically you might hear about

a coronary artery, or a coronary vein, but together you can call them

coronary blood vessels. I'll add the word blood here. So these

coronary blood vessels are actually serving the heart muscle

itself. I mean remember, the heart

is made up of thousands and thousands, actually tens of thousands of cells

and those cells, just like our toe cell that we drew,

they also need oxygen, nutrients, and have waste.

So, those cells are going to need blood vessels supplying

them as well. So, that's what the coronary blood vessels are. They're literally

the blood vessels that go to and serve

the heart. So these are the ones that serve the heart.

Now, if they're serving the heart muscles

and the heart cells, then, think about it, would they fit under

the systemic flow, or pulmonary flow? Well if the

main job is to serve the needs of cells, then

the coronary vessels fall under the systemic flow.