You see that blood blows into the left side of the heart

可以看到血液流入心脏左边
and it's come from the lungs.

它是从肺流出的
The blood has come from the lungs

血液由肺流出
and so it's full of oxygen and in this diagram it's indicated as red.

充满了氧气在这幅图中用红色表示
If you follow the arrows here,

跟着这个箭头
the blood flows from the lungs into the left atrium,

血液由肺部流出流入左心房
into the left ventricle,

进入左心室
and out through a large vessel called the aorta.

由这个叫做主动脉的大血管流出
Fairly simple;

这很简单
so far two chambers in the heart,

目前只讲到了心脏中的两个腔
blood flows through these two chambers,

血液流经这两个腔
atrium first then ventricle,

先心房后心室