Why isn't there a pressure drop through the aorta?

为什么主动脉两侧没有压差
Well there is a pressure drop through the aorta but it's very small.

其实这里存在压差但是极小
The reason it's small is that the aorta is big;

因为主动脉比较粗
has a large diameter and so it's resistance is low.

半径较大所以阻力较小
In order to generate 5L/min of flow you don't need much pressure.

产生五升每分钟的流速无需太大压力
In order to--even this whopping flow that goes through the aorta,

即使是一股洪流通过主动脉
because of the large size of the aorta,

由于主动脉的尺寸较大
you don't need much pressure drop to generate that flow.

形成流动的话就无需太大的压差
If I measured pressure drop over the aorta,

如果测量主动脉两侧的压差
from the beginning to the end of the aorta,

从主动脉起始部至终末部之间的压差
I'd find that pressure doesn't really change very much

就会发现两端压强没多大变化
and that's what's shown in this diagram here.

这就是这张图想说明的内容