Your Heart

The heart is the muscle responsible for pumping oxygenated blood around the body, through repeated rhythmic contractions.  It is made of cardiac muscle, an involuntary muscle tissue which is only found in this organ.

The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδία, kardia, for "heart."

The size of a clenched fist, the average heart weighs about 300g and sits in a sac called the pericardium.  It is positioned in the thorax between your the lungs and with its tip pointing to the left side of your body. 

The heart consists of four chambers, the two upper chambers (atria) and the two lower chambers (ventricles).  The function of the right side of the heart is to collect de-oxygenated blood in the right atrium from the body and pump it, via the right ventricle, into the lungs so that carbon dioxide can be dropped off and oxygen picked up.

The left side collects oxygenated blood from the lungs into the left atrium.  From the left atrium the blood moves to the left ventricle which pumps it out to the body. On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood around the body.

Your heart beats around 70 times per minute at rest, but speeds up when you exercise.  The contractions of your heart are so powerful that it can pump your body’s entire blood volume around your body in just one minute. 

In a lifetime of 80 years, a heart will beat some 3 billion times.