1. Arteries: These carry oxygenated blood away from the heart to the rest of the body. Arteries have thick, elastic walls to withstand the high pressure of the blood being pumped from the heart.
2. Veins: These carry deoxygenated blood back to the heart. Veins have thinner walls than arteries and often have valves to prevent blood from flowing backwards.
3. Capillaries: These are the smallest and most numerous blood vessels, connecting arteries and veins. They have very thin walls that allow for the exchange of oxygen, nutrients, and waste products between the blood and the tissues.