Circulatory System

What Does It Do?

• Your circulatory system continuously delivers blood to all parts of your body, it also returns oxygen-poor blood to the lungs. The circulatory system consists of your:
• Heart, which pumps blood into blood vessels
• Blood vessels, a system of tubes that carry blood to your entire body and back to your heart
• Lungs, which supply oxygen to the blood

You can compare your circulatory system to a “figure eight.” One loop routes blood from the heart to the lungs and back to the heart. On this loop carbon dioxide is removed from the blood, and oxygen is put into the blood. You fill your lungs with oxygen when you breathe in. And carbon dioxide is removed when you breathe out.

The second loop delivers blood—along with oxygen and nutrients—to every other part of your body. The blood vessels then take away waste products (for example, carbon dioxide). Finally, the oxygen-poor blood returns to the heart for more oxygen. The cycle then repeats continuously.

This second loop is large and very complex. To give you an idea, an adult has about 60,000 miles (96,560 kilometers) of blood vessels throughout the body!

Your circulatory system does more than carry oxygen and carbon dioxide, however. It carries nutrients from your intestines to your body’s tissues. It carries hormones to the appropriate parts of your body from your glands. The circulatory system also carries waste products to your liver and kidneys to be removed.