It takes a substantial drop in pressure

为了让低速流体通过较细的血管
in order to move this lower flow rate through these smaller vessels.

确实需要一定的压力
How could that be?

这个压力是多大呢
Well remember that the resistance changed with r4.

还记得阻力是随着半径的四次方变化吧
That means that as the radius goes down

这就是说随着半径减小
it's not a linear relationship between the radius going down

阻力增加和半径减小之间
and the resistance going up,

并非是线性关系
it's a 4th-power relationship.

而是四次方的关系
As it gets small resistance starts to become very, very high.

阻力快速地由小变大变得非常大
When you divide a flow between vessels that's kind of a linear process,

血液被分流至不同血管的过程是线性的
it goes two ways, it goes four ways, it goes eight--

被分成两股四股八股
but this r4 starts to dominate

但随着半径的减小