The heart has four chambers, two upper atria, the receiving chambers, and two lower ventricles, the discharging chambers.
The atria open into the ventricles via the atrioventricular valves, present in the atrioventricular septum.
It is also known as the bicuspid valve due to its having two cusps, an anterior and a posterior cusp.
The cardiac skeleton also provides an important boundary in the heart's electrical conduction system since collagen cannot conduct electricity.
The heart pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node.
These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along the conduction system of the heart.
The largest part of the heart is usually slightly offset to the left side of the chest (though occasionally it may be offset to the right) and is felt to be on the left because the left heart is stronger and larger, since it pumps to all body parts.
Because the heart is between the lungs, the left lung is smaller than the right lung and has a cardiac notch in its border to accommodate the heart.