How a Healthy Heart Works

The heart’s main function is to move oxygenated blood throughout the body. Any blood vessels carrying blood to the heart is a vein, and any blood vessel carrying blood away from the heart is an artery.¹ For example, the vessel carrying blood from the heart to the lungs is named the pulmonary artery, yet the vessel carrying blood from the lungs to the heart is named the pulmonary vein.

There are four main chambers of the heart: two atria (right and left) and two ventricles (right and left).² Between each chamber and between a chamber and a vessel, there is a valve. The valves prevent blood from flowing in the wrong direction through the heart.³

• Between the right atrium and right ventricle: tricuspid valve⁴

• Between the right atrium and pulmonary artery: pulmonary valve⁴

• Between the left atrium and left ventricle: bicuspid valve⁴

• Between the left ventricle and the aorta: aortic valve⁴

Oxygen-poor blood returns to the heart through two main veins: the superior vena cava (SVC) and inferior vena cava (IVC).⁵ The oxygen-poor blood enters the right side of the heart and flows into the right atrium (RA). The blood will continue to flow through the tricuspid valve (TV) and into the right ventricle (RV).⁴ The heart’s muscles contract (what you feel as a heart beat), and this forces the blood from the RV through the pulmonary valve into the pulmonary artery.⁵ During this contraction, due to the pressure build up, the tricuspid valve slams shut and prevents blood from flowing backwards into the RA. In the lungs, the blood will become reoxygenated as it receives oxygen and gets rid of carbon dioxide.² The reoxygenated blood will then reenter the heart through the pulmonary veins into the left atrium (LA). The blood will flow through the mitral valve and into the left ventricle (LV).⁴ The LV is the most muscular chamber of the heart. This is because it must generate the high pressure required to pump blood through the whole body via the aorta.² When the muscles in the heart contract, especially the muscles in the LV’s wall, blood is propelled through the aortic valve and into the aorta. The aorta is the main artery that is responsible for delivering oxygen-rich blood to the body.⁴

Whenever you feel a heartbeat that is the muscle in your heart wall contracting.¹ The contraction decreases the volume in the chambers of your heart, and pushes the blood either to the lungs or to the rest of the body. Your heart has an electrical system that determines how fast your heart beats.^2,5 There are two sounds typically heard when a healthy heart beats: “lub-DUB”. A typical heart first contracts to push blood from the atria into the ventricles (both sides of the heart do this at the same time). Once your atria have finished contracting, and as the ventricles begin to contract, the valves between atria and ventricles close. This generates the “lub” sound. Once your ventricles finish contracting, the valves between the aorta and the LV, and the pulmonary artery and the RV close. This generates the “dub” sound. Therefore, there are 2 contractions for every heartbeat – one that contracts both atria simultaneously, and one that contracts both ventricles simultaneously.