In Depth: Blood Flow
The flow of blood through the heart follows a very deliberate path to ensure that blood oxygenated from the lungs passes through major arteries and delivered to body tissue. This process occurs on an average of 72 times a minute, pumping about 2,000 gallons worth of blood every day.
Regular, rhythmic contraction of the myocardium—the thick, middle layer of cardiac muscle—provides the pumping pressure that allows blood to flow through veins and arteries.
To best explain blood’s journey through the body, let’s start will a single cell’s trip from the tips of one of your fingers to the tip of a toe:
- A blood cell without oxygen will travel through a vein until it meets up with the superior vena cava, a large vein that takes blood from the head and arms to the heart.
- The cell passes the right atrium, where it meets with blood from the lower part of the body from the inferior vena cava.
- After passing through the tricuspid valve, blood is pumped into the right ventricle, which pumps blood through the pulmonary valve and into the pulmonary trunk, a sort of T-intersection in the chest.
- At this point, the cell either goes right or left. For the sake of argument, our cell chooses the left pulmonary artery. It follows that route until it meets capillaries in the left lung where it receives oxygen.
- At this point in the process, the cell will return to the heart via the left pulmonary vein and meet up with other blood from the right lung in the left atrium of the heart.
- The blood then flows down through the mitral valve and into the left ventricle. This is the part of the heart that pumps blood throughout the entire body.
- After a quick burst through the aortic valve, the blood follows through the ascending aorta and out through the circulatory system to that little toe of yours.
- After the organs and muscle tissue use the oxygen, it’ll travel up the inferior vena cava and back to the heart, starting the process all over again.
Because your heart continues this process millions of times a year, it’s important to keep your heart healthy with good diet and exercise.