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Now let's move on again to one final thing I want to point out,
好，我还要强调一点
which is I want to zoom in on the wall.
我们来看这个壁
So here in a grey box I'm going to kind of highlight what's going on in this wall
在这个灰色长方形里，我画一下壁的构成
and how many layers there are in this wall.
这个壁是由好多层构成的
Let me draw out a little rectangle to correspond to that little rectangle I drew on the heart itself.
我用矩形来表示一下心脏上画的这个小矩形
So there are 3 layers to the heart muscle.
心肌有三层
And actually I'm going to go through all three layers,
我给大家介绍一下这三层分别是什么
and we'll start from the inside and work our way out.
我们从内层开始，逐层向外
On the inside you have what's called the endocardium.
最里边的是心内膜
I'm actually going to draw the endocardium all the way around here,
我画一下心内膜沿瓣膜，
it goes all the way around the valves.
这样延伸
So now you've already learned that the valves now have endocardium.
现在大家知道，首先是心内膜
It goes around the ventricle and, as I showed you in the beginning, also around the atrium.
包围心室，刚我也介绍了，也包围心房
It goes all the way up and covers both the right and left side.
把左边和右边都包围起来
The endocardium is very very similar in many ways to the inner lining of the blood vessels actually
实际上，心内膜跟血管内膜是非常相似的
So it's a really thin layer, not a very thick layer.
都是非常薄的一层
And it's definitely, it's the layer that all the red blood cells are kind of bumping up against.
血管内膜是红细胞可以紧密接触到的一层膜
When the red blood cells are entering the chambers of the heart,
一旦红细胞进入心脏
the part that they're going to see is going to be the endocardium.
首先接触到的就是心内膜
So this is what it looks like,
就像这样
and this is that green layer all the way around that I've drawn now.
就像我画的这个绿色的膜
So if I was to draw kind of a blown up version, it might look like this. Right?
画一个放大版的，就是这样
It's a few cell layers thick.
这层膜只有几个细胞的厚度
And like I said on the inside you have some red blood cells bumping along.
红细胞可以紧密接触到这层膜
So manybe this is one RBC,
所以这可能是一个红细胞
this is maybe another one and they would bump into that endocardium.
这是红细胞，它们可能会撞击心内膜
If you go a little bit deeper to that endocardium, what do you get to next?
或者来到这里，那么再向外是什么呢？
Next you get to myocardium.
下一层是心肌层
That would be, I'd say, the biggest chunk of our wall.
这是心脏壁中最大的一部分
And that would look something like this.
就像这样
