Final answer:
The tunica media is the thickest layer present in arteries, accommodating high blood pressure and volume changes, unlike the thinner-walled veins and the single-layered capillaries.
Step-by-step explanation:
The tunica media is larger in the arteries. Arteries have thicker walls than veins and capillaries due to the higher pressure of blood that flows through them from the heart. This layer is crucial as it contains smooth muscle tissues that control the diameter of these vessels, adjusting them to accommodate changes in blood pressure and volume.
Veins, in contrast, have thinner walls with larger lumens and often appear flattened, because they operate under lower pressure. Capillaries have only a tunica intima layer and are the smallest blood vessels, connecting arterioles and venules and facilitating the exchange of substances between the blood and surrounding tissues. The tunica media of arteries is equipped to handle the pulses of pressure from the heart, which is why it's substantially more robust in these vessels.