Final answer:
The order of blood pressure in the major types of blood vessels from least pressure to greatest is veins < capillaries < arteries, with veins having the lowest pressure and arteries the highest.
Step-by-step explanation:
When considering the order of blood pressure in the major types of blood vessels from least pressure to greatest, it is important to understand the circulatory path blood takes as it travels through the body.
Blood is pumped by the heart into the arteries, which branch into smaller arterioles, then to the capillaries where gas and nutrient exchange occurs. After the capillaries, blood enters the venules and then the veins which carry it back to the heart.
Arteries, having to withstand the initial high pressure from heart contractions, have the highest pressure. Capillaries have a lower pressure than arteries but higher than that of veins.
Veins have the lowest pressure because the blood has traveled the farthest from the heart and the pressure has decreased.
The correct order from least pressure to greatest in the major blood vessels would thus be: veins < capillaries < arteries.