The human heart is four-chambered. The upper chambers are called the atria or the auricles and the lower two chambers are called the ventricles. The two atria are separated by the interatrial septum. The two ventricles are separated from each other by the interventricular septum. The ventricles have more muscular walls than the auricles.
The right side of the heart is concerned with deoxygenated blood and the left side of the heart with the oxygenated blood. The right auricle opens into the lower right ventricle. This opening is guarded by auriculo-ventricular valve (auriculo ventricular valve). This valve is called the tricuspid valve as it has three flaps. The flaps of the valves are connected to the walls of the ventricle by tendons called the chorda tendinae.