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It's an amazing pump, pushing blood, so that you have good blood flow.
心臟就是一個泵，不斷把血液抽入，推出，維持血液流動
And so I'm going to write that on the side as kind of job number one.
這是心臟的第一個工作
These are the jobs of the heart.
這邊我們寫一下心臟的工作有什么
So jobs, and number one, would be blood flow.
第一，維持血液流動
And I'll write systemic flow. Systemic flow.
這屬于體循環
And all that systemic means is that I'm refering to the entire body.
體循環就是相對于全身來說的
So systemic when I say that word, I just mean the entire body.
這是針對于全身的
All the cells in the body.
全身的每個細胞
Now, exactly how that happens actually you can see on this picture.
看這個圖，大家會明白原理
So, here you have a giant vein, this is a vein, and you have an artery here.
這里有一條大靜脈，這里有一條動脈
This is an artery.
這是動脈
And blood is actually going through the artery, that way.
血管從這個方向通過動脈
And it's actually coming into two veins, the one at the top,
進入兩條靜脈，一條在上邊
this is called the superior, superior just kind of means at the top.
叫superior--其中superior意思就是上部
Superior vena cava. That's the name of the vein.
這條靜脈叫上腔靜脈
And at the bottom here, you can't see it because it's on the other side of the heart,
而下邊，這里在心臟另一邊，大家是看不到的
but there's another vein called the inferior vena cava.
這里還有一條靜脈，是下腔靜脈
And these two veins, this is also a vein,
這兩條靜脈
these two veins are actually dragging blood in from all over the body, into the heart.
從全身抽取血液回來，流入心臟
And then, when the heart is ready to pump it back out,
當心臟完成工作，要把血液送回全身時
it goes into this artery, and the name of it is the aorta.
就把血液送到這條動脈，名字是主動脈
So if you've heard of the aorta,
大家可能聽說過主動脈
this is the artery that people are talking about.
說的就是這條動脈
So this is how blood comes and gets pumped around.
這是血液流出心臟的通路
But this isn't actually the only job of the heart.
當然，這不是心臟唯一的工作
The job, the second job of the heart, is actually also in this picture, and it's called pulmonary flow.
心臟還有第二個工作也在圖中標出了，叫做肺循環
Pulmonary flow. So, what does that mean?
肺循環是什么意思呢？
Well, we know that cells are expecting oxygen, right?
我們知道細胞生存需要氧氣
We know this. And that they have a lot of carbon dioxide waste.
同時產生很多二氧化碳廢物
Well, it's good to move things around.
這些物質都需要搬運
It's good to move blood around.
血液需要流動
But if you actually never got rid of that carbon dioxide or brought in new oxygen,
但除非丟掉這些二氧化碳廢物，或者說補充氧氣
then a cell is not going to be very happy either.
細胞才能持續存活
I mean, you can have blood flow,
所以只有血液循環是不夠的
but at some point it's also going to want some oxygen.
還要補充氧氣
And it's going to want to get rid of that carbon dioxide.
同時要把二氧化碳代謝出去
So, that's where the lungs come in.
這時就要考慮到肺了
So what happens is that the heart, before sending blood out the aorta,
在心臟把血液送入主動脈之前
before just dishing it back out to the body,
送回身體各處之前
it actually sends the blood over to the lungs.
先把血液送入肺部
And it goes over to the left lung, and to the right lung.
進入左肺和右肺
And the blood comes back from the right lung and the left lung,
經過兩個肺之后
and gets pushed back into the heart, and then gets squeezed through the aorta.
送回心臟，再送入主動脈
So there's this actual extra little step here,
在肺中的這個步驟
where blood is going to and from the lungs, and that's the pulmonary flow.
這個過程叫肺循環
