Figure 3
From: A self-avoidance mechanism in patterning of the urinary collecting duct tree
Patterning of tubule trees by self-avoidance, in a simple model. Beginning with an unbranched trunk (a), secreting the repulsive factor horrid, the model produces a tree (b), in which the first angle of branching is wide and subsequent angles narrower although this change is not written explicitly into the model, but emerges from self-avoidance. If two trunks are aimed at one another, either directly (c) or offset (d), they each produce a tree that is distorted but that avoids collision with the other tree.