Illustration of simple systems in the vessel network.

<p>The icons are borrowed from the electrical circuit <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045444#pone.0045444-Hacking1" target="_blank">[30]</a>. (A) A vessel is in series with a fixed resistance . (B) The parallel part of two vessels is in series with a fix resistance. (C) The parallel part is controlled by the open-close switches.