(i) The heart is composed of two types of chambers. The upper two, small, thin walled chamber are the auricles or atria and receives blood from various parts of the body and lower two large, thick walled muscular ventricles that supply blood to various body organs.
(ii) The two auricles are separated by inter-auricular septum.
(iii) The right atrium receives the openings of superior vena cava, inferior vena cava and coronary sinus.
(iv) The opening of inferior vena cava is guarded by eustachian valve.
(v) The opening of the coronary sinus has Thebasian valve.
(vi) The left auriculo-ventricular valve consists of two flaps and is termed bicuspid or mitral valve.
(vii) The right auriculo-ventricular valve consists of three triangular flaps and is called tricuspid valve.
(viii) The right and left ventricles are separated by interventricular septum.
(ix) The ventricles function as pumping chambers, thus they have thick muscles walls.
(x) Attached to the flaps of the bicuspid and tricuspid valves are special fibrous cords, the chordae tendineae, which are joined to the other ends with the special muscles of the ventricular wall, the papillary muscles.
(xi) The openings of the right and the left ventricles into the pulmonary atery and the aorla respectively are provided with the semilunar valves.
