7.2 The human heart

7.2.2 Description

The heart functions as a pump, providing a continuous vital circulation of blood through the body, by way of cardiac cycles. It is contained in the thoracic cavity of the thorax in a section called the mediastinum.

The pericardium is the protective sac which surrounds the heart and also contains lubricating pericardial fluid. The heart has a wall of three layers, the epicardium, the myocardium (which is the muscle of the heart), and the endocardium. There are four main chambers in the heart: the two upper chambers are the atria (right and left atrium) and the two lower chambers the ventricles (right and left.) The septum is the dividing wall of muscle separating the right and left sides of the heart. The ventricular septum is thicker than the atrial septum.

Physicians who study the human heart and its disorders (cardiovascular diseases) are called cardiologists. They often refer to the right atrium and right ventricle as the right heart and the left atrium and left ventricle as the left heart. With each heartbeat, the right ventricle would normally pump the same amount of blood into the lungs as the left ventricle would pump out into the body. The ventricles are the discharging chambers and the atria the receiving chambers.