The Heart The heart is a muscular pump divided into two separate but physically joined organs - the right heart and the left heart.

The left heart pumps blood via the aorta artery into the systemic arteries, bringing necessary oxygen and nutrients to all parts of the body. The right heart sends blood via the pulmonary artery into the smaller blood vessels of the lungs, allowing the lungs to extract oxygen efficiently and eliminate carbon dioxide.

The right and left hearts each have two chambers. The upper chambers are atria; the lower chambers are ventricles.

Heart Valves

There are four heart valves - doors that keep the blood moving in a single direction through the heart.

They are the:

• tricuspid valve regulating blood flow between the right atrium and right ventricle
  
  
• pulmonic valve managing blood flow between the right ventricle and pulmonary artery
  
  
• mitral valve controlling blood flow between the left atrium and left ventricle
  
  
• aortic valve regulating blood flow between the left ventricle and the aort

Blood enters the heart through the right atrium, which then contracts and sends it to the right ventricle. The right ventricle contracts and propels the blood into the blood vessels of the lungs.

Full of oxygen, the blood leaves the lungs and reenters the heart through the pulmonary veins, which empty into the left atrium. The left atrium contracts and thrusts the blood into the left ventricle. The left ventricle contracts and sends the blood to the body and brain via the aorta and its branches.

During each heartbeat, valves open and close in a complex sequence that ensures efficient forward movement of blood.

The tricuspid and mitral valves open to allow blood to flow into the ventricles from the atria. During this time, the pulmonic and aortic valves are closed preventing leakage back into the ventricles of the blood ejected during the previous beat.

As the newly-filled ventricles contract, the pulmonic and aortic valves open, enabling blood to leave the heart. During this time, the mitral and tricuspid valves are closed preventing blood from flowing back into the atria.

Valves are essential to the efficient movement of blood throughout the heart and into the body.