The circulatory system’s main function is to deliver oxygen and food to every cell in the body, as well as remove waste products like CO2.
This system is powered by the heart. The main function of the heart is to pump blood around the body. The heart has 4 main chambers; right and left atria on top of the right and left ventricles. The veins that lead to the right and left atria are called the vena cava and the pulmonary vein. The arteries that come out of the right and left ventricles are called the pulmonary artery and the aorta.
The image below is the cross-section of a human heart.
The steps the heart takes to pump blood around the body are:
- Blood flows into the right and left atria through the vena cava and the pulmonary vein.
- The two atria contract, pumping the blood into the ventricles.
- The right and left ventricles contract pumping blood to the rest of the body through the pulmonary artery and aorta.
- More blood enters the two atria and the cycle starts over.
The ventricles have more muscle than the atria because ventricles have to pump blood out of the heart, not just to another chamber in the heart. The left ventricle has more muscle than the right ventricle because the right ventricle only has to pump blood to the lungs, while the left ventricle has to pump blood to all other organs in the body.