ARTERIES & VEINS

CIRCULATION

ARTERIES & VEINS• Arteries carry oxygen-rich blood away from the heart.• Veins carry oxygen-poor blood back to the heart.• Blood begins its vascular system voyage at the right side of the heart,

where the pulmonary artery is located. This artery carries the oxygen-poor blood to the lungs where it receives oxygen from the alveoli and rids of carbon dioxide.

• The pulmonary vein then carries oxygen-rich blood back to the heart. The blood travels to the left side of the heart and is pumped throughout the entire body.

• The main and largest artery leading from the heart to the rest of the body is called the aorta.

• As blood travels, it moves from large arteries to smaller and smaller vessels. In this way every individual cell is delivered oxygen and essential nutrients in order to function properly. The blood also picks up waste material and carbon dioxide from the cells it visits.

• The blood then begins a trip back to the heart through veins. First moving through smaller veins then entering larger and larger veins as it goes moves closer to the heart. The blood also passes through the liver to drop of waste products . Eventually it returns to the right side of the heart and the cycle begins again.

ARTERIES

• Arteries are tough, elastic tubes that carry blood away from the heart. As the arteries move away from the heart, they divide into smaller vessels. The largest arteries are about as thick as a thumb. The smallest arteries are thinner than hair. These thinner arteries are called arterioles. Arteries carry bright red blood. The color comes from the oxygen that it carries.

VEINS

• Veins carry the blood to the heart. The smallest veins, also called venules, and are very thin. They join larger veins that open into the heart. The veins carry dark red blood that doesn't have much oxygen. Veins have thin walls. They don't need to be as strong as the arteries because as blood is returned to the heart, it is under less pressure.

Arteries & VeinsSimilarites

• Both arteries and veins are blood vessels which make up the circulatory system.

• Arteries and Veins both carry blood in tubes throughout the body.

Differences•Arteries carry oxygen-rich blood away from the heart.

•Veins carry oxygen-poor blood to the heart.

•Arteries have thick, elastic walls which constantly change their size in order to cope with fluctuating pressure from the strong pumping of the heart.

•Veins have very thin walls and do not contract.

•Blood in arteries moves faster than the blood in veins as they are under greater pressure.

•Blood flow in veins depends on valves which prevents the backward flow of blood and surrounding muscles.