This backward flow is prevented thanks to four one-way valves.

由于是单向瓣膜，因此预防血液回流。

The valves open as blood moves toward the heart and then close to prevent the backward flow of blood.

当血液流向心脏时，瓣膜打开，然后关闭，以防止血液回流。

It ends with the ileocecal valve, which prevents intestinal contents from going into the large intestine too quickly and the backward flow of material.

末端回肠结束于回盲瓣；回盲瓣可以防止肠内容物过快进入大肠以及肠内容物返流。

When the ventricles contract, blood in the right ventricle is forced through the pulmonary semilunar valve into the pulmonary artery; at the same time, the tricuspid valve closes to prevent the backward flow of blood into the atrium.

进入肺动脉的血液被运至肺，进行氧合过程，即与周围环境进行氧及二氧化碳（细胞的一种代谢废物）的交换。