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Introduction to the Heart
What does the heart do?

Our heart is essentially two distinct, but anatomically connected pumps:

  1. Right side – Receives blood from body and pumps blood into lungs to gather oxygen
  2. Left side – Receives oxygenated blood from lungs and sends out to body

The PULMONARY circulation is responsible for taking up oxygen and releasing carbon dioxide. The SYSTEMIC circulation delivers the oxygenated blood to our tissues.


It may seem odd that the right and left sides on the diagram appear reversed. This is because all references to the right or left side of the heart use our outside point of reference (as if they are facing you for inspection). Problems can arise with either the right or left side of the heart alone, but this will ultimately lead to complications for the other side of the heart. The normal adult human heart weights about 11 ounces (0.3 kilograms) and is about the size of a clenched fist. Click here for anatomical diagrams of the heart.

How does the heart work?

Electrical signals travel through specific cell pathways in the heart that signal and stimulate the heart to pump. In response to this, the chambers of the heart rhythmically contract to push blood into circulation — first the atria contract, then the ventricles. In the average lifetime, the heart will beat more than one billion (1,000,000,000) times! The ventricles do the majority of the work pushing the blood through the body. Blood typically leaves the heart at a speed of about one foot per second (0.3 meters per second) but can rise to nearly six feet per second with moderate activity. The atrial contraction assist in filling the ventricles with more blood to push out of the heart. People can survive with atria that do not contract efficiently; however, if the ventricle stops pumping, death occurs within minutes! As much as it is the heart’s job to push the blood to deliver oxygen to all tissues, it also must have its own supply of oxygen to perform work. It receives this oxygen from the coronary arteries. If this supply is interrupted, heart tissue can die causing a heart attack- a possible cause of the onset of heart failure. For further explanation of this topic click here.