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Let's talk about blood vessels
這集我們接著看血管的內容
I'm going to talk to you about the different types of blood vessels that there are
我們要考慮的就是不同的血管類型
and we're going to see if we can come up with some general patterns.
我們看不同的血管，看能不能找到什么共同的規律
So let's start with the uh
首先我們來看
let's say we take the blood vessel out of your body and we examine it under a microscope.
假設我們取出一條血管，拿到顯微鏡下觀察
It would look something like this,
差不多就是這樣的
where you have the middle: called the lumen.
最中間是內腔
And right outside of the lumen you have cells.
內腔外邊是一層細胞
And these cells are going all the way around the lumen
這些細胞緊密包圍血管內腔
and they're the first type of cell that any blood would interact with, right?
同時它們也是跟血液接觸的第一類細胞
Because that's right immediately outside of the lumen.
因為它們是與內腔緊密接觸的
And on the other side of the cells, on the back side of the cells
細胞的另一邊，或者如果把內腔看成細胞的前邊的話
if you think of the lumen as the front side- is a little line I'm gonna draw here
我們看細胞層的后邊我們畫一條線
to represent protein that sits there and acts as a scaffold,
代表這層起支架作用的蛋白質
kind of like keeping all of the cells in place.
保持細胞緊密接觸內腔
So you have all of these endothelial cells.
這些是內皮細胞
And then you have that little base membrane- like a thin line of membrane- called the base membrane
然后是基膜，就是薄薄的一層膜
And that keeps everything from falling out of place.
作用是保持內部的結構不變
And the thing that's in the base membrane is mostly protein.
基膜中的物質，基本就是蛋白質
So think about things like collagen which you can find in bones and your gums.
比方說，大家想一下骨骼或者牙齦中的膠原
That same protein is actually lining all of these blood vessels that are in your body.
同樣的蛋白質也存在于血管中
And together the base membrane and endothelial cells,
而基膜和內皮細胞
they make up a layer called the Tunica- write it nice and big- Intima.
統稱內膜，首字母大寫，
They make up a layer called the Tunica Intima.
它們構成內膜
And that's kind of the word we use because "tunica" comes from the word for coat or cloak.
大家看這個名詞"Tunica Intima"，tunica意思是“表面”
And "intima" is kind of the intimate layer, the intimate coating of the vessels
intima意思是“內層”，代表血管的內層
So Tunica Intima.
這就是血管內膜
Now right outside of this is another layer- and I'm gonna draw that here in red.
在內膜的外邊，我用紅色畫這一層
And this will be a layer of muscle.
這是一層肌肉
Imagine these little lines represent smooth muscle cells.
這代表一層平滑肌細胞
So this would be muscle and this would be the layer called tunica media, or middle.
這是肌肉細胞，這層叫做血管中膜
And the most important thing here is that there is smooth muscle in this layer.
最重要的一點就是記住，這層中有平滑肌細胞
And finally, on the very outside, you have another layer.
最后，是外層
And I'm gonna draw it as a yellow line.
我用黃線畫
And this yellow line represents more protein.
黃線代表的還是蛋白質
This is another layer of protein, just like the base membrane,
這是另一層蛋白質，就像基膜那樣
but different composition of proteins.
只不過蛋白質的成分不同
But again you see actually a lot of collagen, just as before, and some other proteins as well.
還是大量的膠原，同時有一些其他的蛋白質
And this is called the tunica externa, for external layer.
這層叫做血管外膜
Actually another word that they sometimes use for this is called "Adventitia."
或者還有一個術語是Adventitia
So you might see that word too.
它的意思也是外膜
And the really interesting thing about the tunica externa is that you actually, on the large vessels,
外膜有一個特點，就是對一些大血管來說
you find that they need blood to supply themselves,
它們也需要血管提供營養
so some of these large vessels have little blood vessels on them.
所以有的大血管外壁上有小血管
