Circulatory Organ
noun
You already know that 循環 means "circulation," so adding container makes it what holds things that circulate. They're your circulatory organs. They contain all the blood moving throughout your body like a container.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
当院には、循環器専門医が五人います。
There are five circulatory organ specialists in this hospital.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.