How many chambers are in a heart?

The heart consists of 4 chambers - 2 atria and 2 ventricles. The smaller atria are about 1/3 the size and volume of the ventricles. The left ventricle is the largest chamber of the heart, with about 3 times more muscle mass than the right ventricle - both ventricles share a similar volume capacity. Due to the predominant size of the left ventricle, it is not surprising that 70% of all myocardial infarctions occur within the left ventricle. While the heart's chambers' primary purpose is to fulfill the mechanical function of pumping blood, other functions include influencing heart rate and serving several endocrine roles.