The human heart consists of four chambers. These are-
(i) Right atrium: The right atrium is large and covered by a thin membrane. Above it is the superior vena cava and below it is the inferior vena cava. It carries CO2-rich blood to the right ventricle through the tricuspid valve.
(ii) Left Atrium: The left atrium is slightly smaller and covered with thick walls. It is connected with the pulmonary vein. It carries O2-rich blood to the left ventricle through the bicuspid ventricle. Between the two atria is the inter-atrial septum.
(iii) Right Ventricle: The right ventricle is slightly larger and covered with a thick wall. It has a tricuspid capsule on one side and a semilunar capsule on the other. It carries CO2-rich blood to the pulmonary arteries through the semilunar capillaries.
(iv) Left Ventricle: The left ventricle is slightly smaller and covered with thick walls. Its wall is three times as thick as the wall of the right ventricle. Fleshy columnar corni arise from the walls of the ventricles. It has a bicuspid lens on one side and a semilunar lens on the other. It carries O2-rich blood through the semilunar capillaries into the aorta or aorta. Between the two ventricles is the interventricular septum.