Combined with the cardiovascular system, the circulatory system helps fight disease, help the body maintain a normal body temperature, and provide the right chemical balance to provide the body’s homeostasis, or state of balance among all its systems.

The circulatory system consists of four major components:

  • The Heart: About the size of two adult hands held together, the heart is located near the center of the chest. Thanks to its consistent pumping action, the heart keeps the circulatory system working at all times.
  • Arteries: Arteries carry oxygen-rich blood away from the heart, and to their designated organ or tissue.
  • Veins: Veins carry oxygen-depleted blood to the lungs, where the blood gets replenished with fresh oxygen.
  • Blood: Blood is the transport media of nearly everything within the body. It transports hormones, nutrients, oxygen, antibodies, and other important things needed to keep the body healthy.

Oxygen enters the bloodstream through tiny membranes in the lungs that absorb oxygen as it is inhaled. As the body uses the oxygen and processes nutrients, it creates carbon dioxide, which your lungs expel as you exhale. A similar process occurs with the digestive system to transport nutrients, as well as hormones in the endocrine system. These hormones are taken from where they are produced to the organs they affect.

The circulatory system works thanks to constant pressure from the heart and valves throughout the body. This pressure ensures that veins carry blood to the heart and arteries transport it away from the heart. (Hint: to remember which one does which, remember that that “artery” and “away” both begin with the letter A.)

There are three different types of circulation that occur regularly in the body:

  • Pulmonary circulation: This part of the cycle carries oxygen-depleted blood away from the heart, to the lungs, and back to the heart.
  • Systemic circulation: This is the part that carries oxygenated blood away from the heart and to other tissues of the body.
  • Coronary circulation: This type of circulation provides the heart with oxygenated blood so it can function properly.