One of the most important components and part of the cardiovascular system is definitely the heart.
The heart lies in the center region of the thoracic cavity and is suspended by its attachment to the great vessels within a fibrous sac know as pericardium. A small amount of the fluid is present within the sac, that is pericardial fluid. The main task of pericardial fluid is lubrication of the hearts surface allowing it to move freely during functioning (i.e. cycles of contractions and relaxations). The pathway of blood flow through the heart and lungs could be shown as in the following illustration.
The heart has four chambers – two atria and two ventricles – divided into two groups, often referred to as the left and right heart. The chambers of the left heart are the left atrium (LA) and the left ventricle (LV), while the chambers of the right heart are the right atrium (RA) and the right ventricle (RV).
The atria (the receiving chambers) receive the blood from the veins and fill the ventricles (the discharging chambers), which push the blood out through the arteries. The ventricles are filled with the blood from the atria through the atrioventricular (AV) valves (the mitral or bicuspid valve between the LA and the LV and the tricuspid valve between the RA and the RV). The AV valves are passive and open depending on the pressure inside the chambers. When the pressure in the atria exceeds the ventricular pressure, the AV valves open.
Similarly, when the pressure in the ventricles