Figure 2.

Illustration of the different closure methods between arterial and venous trees. Left Column) In Step 1, a single arterial terminal is joined to the venous tree while in the Right Colum corresponding to Step-2, a venous terminal is closed. The Top Row shows the terminal matching (Method 1) where each terminal from the arterial tree must be paired to a terminal in the venous tree. The Second Row (Method 2) attaches each terminal to a nearby segment of the opposite tree through a new bifurcation in the opposing tree. In the Third Row (Method 3), each terminal attaches to two nearby segments of the opposite tree through two new bifurcations. The closure algorithm repeatedly adds connections in reciprocal manner (arterial closure-step-1, venous closure-step-2) until all terminals are closed on both trees.