But, unlike the tricuspid valve, the pulmonary valve doesn't have any of those chordae tendineae.

但三尖瓣不同，肺动脉瓣没有索。

Both of these have chordae tendineae coming off of them that tether the valve to the papillary muscles in the left ventricle.

这两种都有索，连接到左心室的乳上。

When the heart contracts, that papillary muscle keeps the chordae tendineae taut; and both of these help to prevent regurgitation of blood back into the atrium, allowing it to only flow out the next valve.

当心脏收缩时，乳索绷紧；两者有助于防止血液反流到心房，血液只能从下一个瓣膜流出。

And each cusp looks kind of like a parachute, because it has tiny little strings, called chordae tendineae, coming off of it that tether the cusps to a small muscle called the papillary muscle.

每个尖瓣看起来就像一个降落伞，因为它有很小的弦，叫索；索将尖瓣连接在一块叫做乳的小肉上。