Vital veins
Leaves, like people, have veins. Like human veins, they transport elements that are essential to the body. In fact, they "irrigate" the leaves. These veins contain two kinds of conductive tissue: xylem (which conducts the water and nutrients needed by the leaf's cells) and phloem (which takes the sugars produced by photosynthesis from there to the rest of the tree).
On top of this heavy responsibility, veins act as the leaf's skeleton, supporting it and preventing it from collapsing under its own weight – just as our bones do for us.
