Figure 3. Bifurcation angles resulting from vessel sprouting and connection.

(A) A sprout at 90° to the parent vessel creates initial bifurcation angles of 90°, 90° and 180°. A sprout forming a connection to an existing vessel creates initial bifurcation angles of θ, 180°−θ and 180°, where θ depends on the direction from which the sprout approaches. (B) Migration through the tissue (short blue arrows) driven by tension in each segment and the resulting imbalance of forces acting within the network results in a reduction of the 180° bifurcation angle and increases in the other two angles.