The Heart as a Pump
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The average heart beats 100,000 times each day. Over the course of an average 70-years lifetime, the heart will beat more than a billion times.
The wall of the heart is made up of three layers:
- the outer layer or pericardium
- the middle layer or myocardium
- the inner layer or endocardium
The pericardium and endocardium are thin, protective layers. The myocardium is the thick, muscular layer that provides the strength for the heart to function as a pump.
The heart has four chambers. Blood enters into the two chambers (atria) at the top, and is pumped out by the two chambers (ventricles) at the bottom of the heart. The right and left sides of the heart are separated by a wall (septum). The left side of the heart consists of a top chamber (left atrium) separated from the bottom chamber (left ventricle) by a one-way valve. The left ventricle has a very thick muscle wall that enables it to function as a high-pressure pump. The right side of the heart consists of a top chamber (right atrium) separated from the bottom chamber (right ventricle) by a one-way valve.
