What Is the Circulatory System? 3 Main Parts & Their Functions

What Are Parts of the Circulatory System?

There are many parts of the circulatory system which all work together to keep the body’s cells functioning.

• Blood
  • Red blood cells carry oxygen
  • White blood cells are part of the immune system
  • Platelets are needed for clotting
  • Plasma helps the body distribute nutrients and remove waste
• The heart
  • Sits inside the chest slightly to the left, in front of the lungs, and pumps blood around the body
  • It has four chambers that contract, and valves that make the sound of the heartbeats
    • The right upper chamber (atrium) takes in deoxygenated blood full of carbon dioxide
    • The blood is squeezed down into the right lower chamber (ventricle) and travels through an artery to the lungs where carbon dioxide is replaced with oxygen
    • The oxygenated blood travels back to the heart, entering the left upper chamber (atrium)
    • It is then pumped into the left lower chamber (ventricle) and then into an artery called the aorta where the blood travels throughout the body again
• Blood vessels
  • Arteries
    • They are muscular and pump oxygenated blood from the heart
    • The largest artery is the aorta, which connects to the heart and takes in oxygenated blood from the left ventricle
  • Capillaries
    • The smallest blood vessel; so small blood cells can only move through them one at a time
    • Oxygen and food nutrients move through capillaries to the cells
    • Capillaries also connect to veins, so wastes from cells can be picked up by the blood
  • Veins
    • Have one-way valves instead of muscles, so blood doesn’t go the wrong way
    • They carry deoxygenated blood from the body to the heart, where it can be sent to the lungs
    • One exception is the network of pulmonary veins, which take oxygenated blood from the lungs to the heart