What are the 4 chambers and what is the function of each?

The circulatory system has 4 chambers - 2 Atria and 2 ventricles.
2 Atria - the left atrium receives blood from the pulmonary (lung) circulation, and the right atrium receives blood from the venae cavae (venous circulation). The atria receive blood while relaxed (diastole), then contract (systole) to move blood to the ventricles.

2 Ventricles - two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.