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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.

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Glossary

Glossary entries within this article:

Acute myocardial infarction
- A heart attack which occurs when the supply of blood to part of the myocardium, the heart muscle, is seriously impaired or stopped.
Aorta
- The chief artery that receives blood from the left ventricle of the heart and causes it to flow to the body.
Aortic valve
- Heart valve between the aorta and the left ventricle.
Atria
- The small upper chambers of the heart, also referred to as auricles.
Atrial septum
- Wall that divides the left and right atria.
Atrioventricular canal defect
- (A-V canal defect) A congenital abnormality in which there are defects between the atria and ventricles while the tricuspid and mitral valves are abnormal. Also called atrioventricular septal defect and endocardial cushion defect.
Atrioventricular node
- Conductive tissue at the bottom of the right atrium where electrical pulses must pass in order to reach the ventricles.
Atrium
- The heart chamber which collects blood returning from the rest of the body. In all vertebrates apart from fish there are two atria, one on the left and one on the right. The atrium on the right collects deoxygenated blood from the body and passes it to the right ventricle. The atrium on the left collects oxygenated blood from the lungs and passes it to the left ventricle.
Blood pressure
- Pressure which is exerted by the heart when it pumps blood.
Endocardium
- Interior lining of the wall of the heart.
Congestive Heart Failure
- Condition in which the heart is unable to pump sufficient blood to meet the requirements of the other organs in the body.
Ischemic heart disease
- Disorder caused by insufficient blood supply due to a constriction of coronary arteries.
Myocardium
- Muscle of the heart wall which contracts in order to expel blood.
Pericardium
- A membrane sac surrounding the heart and vessels close to the heart.
Septum
- Wall dividing the chambers of the heart.
Ventricle
- Heart chamber which is responsible for pumping blood to the rest of the body. There are two ventricles in mammals and birds, one on the left and one on the right. The right ventricle pumps deoxygenated blood via the pulmonary artery to the lungs; the left ventricle pumps oxygenated blood to the body via the aorta.

In the glossary you will find terms that we have provided with some extra-information.

Glossary

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