And to do that, the aortic valve, on the left side, and the pulmonic valve, on the right side, quietly open up.

为泵出血液，左边的主动脉瓣以及右边的肺动脉瓣安静地打开。

Right after the S1 sound, the aortic and pulmonic valve open up allowing blood to get pushed out to the body and this period of time is called systole.

在S1之后，主动脉瓣和肺动脉瓣打开，分别使得血液流入身体各组织以及肺部，这段时期叫做心脏收缩期。

The second heart sound, " dub" , is called S2, and the noise comes from the aortic and pulmonic valves snapping shut to prevent blood from flowing backwards after it leaves the ventricles, effectively ending systole.

第二心音“dub”，它被称为S2，声音来自主动脉瓣和肺动脉瓣关闭，以防止血液在离开心室后反流，有效地结束心脏收缩。