How does blood move inside your heart? How does it move to the right and left ventricles, the lower chambers, the aorta, the major veins, and to the lungs?
The blood flows in two separate loops.
The right side of the heart controls the pulmonary loop.
The left side of the heart controls the systemic loop.
The Pulmonary Loop
Blood enters the heart through two large veins, the superior vena cava (9) and the inferior vena cava (10), emptying oxygen-poor blood from the body into the right atrium (11).
Blood flows from the right atrium into the right ventricle (1) through the open tricuspid valve. When the ventricles are full, the tricuspid valve shuts. This prevents blood from flowing backwards into the atrium while the ventricle contracts.
When the ventricle contracts, blood leaves the heart through the pulmonic valve and moves through the pulmonary arteries (2) to the lung capillaries (3).
Here, carbon dioxide passes from the blood to the lungs, and oxygen moves from the lungs into the blood.
The oxygenated blood travels through the pulmonary veins to the left atrium (4).
The Systemic Loop
Blood flows from the left atrium into the left ventricle (5) through the open mitral valve. When the ventricle is full, the mitral valve shuts. This prevents blood from flowing backward into the atrium when the ventricle contracts.
Blood leaves the heart through the aortic valve into the aorta (6).
The aorta branches just above the heart to form the arteries that supply blood to the upper and lower body.
The arteries divide into arterioles and then into capillaries (7 and 8).
The capillaries join together to form the venules that feed the veins.
All of the blood from the body is eventually collected into the two venae cavae, and the cycle repeats.
It takes about 30 s for a given portion of the blood to complete the entire cycle: from heart to lungs, back to the heart, out to the body, and back to the heart.