diffusion is a process where molecules move from areas of high concetration to low concentration. How might this process be altered if there were fewer blood vessels intertwined with the tubules?

Fewer the blood vessels then fewer diffusion of toxins toward tubules.

Explanation:

Nephrons have tubules which are responsible for the removal of wastes and toxins from blood. There is always high concentration of toxins in blood and they will move to nephron's tubules (low concentration) for their removal. Thus, if there is less blood supply to tubules then their is less diffusion of toxins toward tubules.