Veins and arteries reflect back on nature, as they naturally give off smaller and smaller branches, just like how veins and arteries end up in smaller and smaller blood vessels.
The veins and arteries of the body are similar to the representation of a tree, where a single large trunk gives off smaller branches, and then divide to become even smaller branches and so on, until they become too small to see with the human eye.
The veins and arteries can keep on going and going throughout the whole body, just like how tree roots are continuous and can just keep on growing longer and longer.