Final answer:
It is true that on a retinal exam, veins are larger than arterioles, which is a consistent trait throughout the circulatory system; veins have thin walls and large lumens compared to the thick walls and smaller lumens of arterioles.
Step-by-step explanation:
On a retinal exam, it is indeed true that the veins are larger than the arterioles. In the general circulatory system, this is explained by the difference in structure between veins and arterioles. Veins are typically thin walled, with large lumens, operate under low pressure, and have valves. When examining the retinal blood vessels specifically, you'll find that veins have larger diameters compared to the arterioles.
Arterioles, on the other hand, have thicker walls than veins and smaller lumens because they are closer to the heart and handle blood flowing at a greater pressure. The smaller lumen helps maintain this pressure, giving arterioles a more rounded appearance in cross sections than the lumens of veins.