Heart

Heart is pumping blood and oxygen into body parts. One of its main role is actually to send oxygen contained in the circulatory system into each body parts reserve connected to it.

Sending oxygen to body parts

On each pulse, heart send oxygen to each connected body parts. Connected body parts are all parts linked to heart through a chain of circulatory layers present in adjacent body parts, including internal ones.

Heart uses the body part parent hierarchy to decide what is connected to it.

Indeed, on human, the torso is the root of the body part parent hierarchy.

Heart should check then what are the children of the torso to know which body parts are connected to it.