Blood flows throughout the body. Oxygen depleted blood returns from

your lower body to your right side of the heart through your inferior

vena cava. Oxygen depleted blood returns from your upper body to your

right side of the heart through your superior vena cava. The blood goes

to the right side of the heart and into the right atrium. It then goes

through the tricuspid valve and into the right ventricle.

Blood then travels through the pulmonary valve and through your

pulmonary artery. The pulmonary artery takes the blood to the lungs to

be re-oxygenated. Hemoglobin allows this to happen because it allows

the attachment of oxygen molecules to the red blood cells. The oxygenated

blood then returns to the left side of the heart by your pulmonary vein.

The blood enters the left atrium, through the mitral valve, into your left

ventricle. From your left ventricle, blood travels through your aortic

valve, and into the aorta. The aorta disperses the oxygenated blood

throughout the body. Capillaries allow this to happen because they

connect arteries to veins. The septum is what separates the left side of

your heart from the right.