Capillaries; veins; arteries
Capillaries allow materials to be exchanged between the blood and tissues, veins carry blood towards the heart, and arteries carry blood away from the heart.
Capillaries are small blood vessels through which molecules such as oxygen and glucose enter the cells.
Veins are tubes or blood vessels that transport blood toward the heart. Veins mostly transport deoxygenated blood towards the heart except the pulmonary and umbilical veins, which transports oxygenated blood toward heart.
Arteries are blood vessels that transport blood away from the heart to other parts of the body. Arteries have elastic walls and they are stronger and thicker than veins.
