They have special, sort of valves in their circulatory system that does actually stop the pooling of blood in the head.

它们的循环系统内有象是瓣膜一样的特殊构造，防止血液冲向头部。

The organ most relevant to engineers, though, is the heart, a system of valves and chambers that squeeze and relax up to a hundred times a minute to send blood around the body.

然而，与工程师最相关的器官是心脏，它是一套由瓣膜和腔体组成的系统， 每分钟收缩和放松多达一百次， 将血液输送到全身。