Final answer:
Veins have valves that prevent backflow of blood and carry blood to the heart at a low pressure, whereas arteries carry blood away from the heart at high pressure without valves.
Step-by-step explanation:
The major distinction between veins and arteries is that veins have valves while arteries do not. The function of these valves in veins is to prevent the backflow of blood, promoting a unidirectional flow toward the heart. This is necessary because veins carry blood under significantly lower pressure than arteries. Arteries, on the other hand, carry blood away from the heart and have thick walls to handle the high pressure of blood pumped directly from the heart's contractions.
Arteries are defined as blood vessels that carry blood away from the heart, with most arteries, except for the pulmonary artery, carrying oxygenated blood. Veins, including the large inferior vena cava, transport deoxygenated blood toward the heart, being assisted by the valves to counteract gravity and the lower pressure in veins compared to arteries.