The heart is a double pump with four chambers and four one-way valves. Watch oxygen-poor blood leave for the lungs on the right, and oxygen-rich blood set off for the body on the left.
The heart is a muscular pump about the size of a clenched fist, sitting between the lungs. It is really two pumps side by side: a right side that sends blood a short trip to the lungs, and a left side that drives the same blood all the way around the body. Each side has a receiving room (an atrium) on top and a pumping room (a ventricle) below.
From the outside the heart is just a lump of muscle. Everything that matters — the four chambers, the four valves, and the two separate circuits — is hidden inside. Opening it up shows how one beat moves blood through both loops without ever mixing the two.
Oxygen-poor blood coming back from the body collects in the large vena cava and flows down into the right atrium, the upper chamber on the right.
As the right atrium contracts, the tricuspid valve opens and blood drops into the right ventricle below. When the ventricle squeezes, the same valve snaps shut so blood cannot go back up.
The right ventricle contracts and pushes blood through the pulmonary valve into the pulmonary artery, which carries it to the lungs. There it releases carbon dioxide and picks up fresh oxygen.
The now oxygen-rich blood returns through the pulmonary veins into the left atrium. This is the start of the second loop, which serves the whole body.
The left atrium contracts, the mitral valve opens, and blood fills the left ventricle — the chamber with the thickest, strongest wall.
The left ventricle contracts powerfully, the aortic valve opens, and blood is driven into the aorta and on to every part of the body. Then the cycle repeats, beat after beat.
Two separate loops need four chambers. The right side pumps blood a short way to the lungs, and the left side pumps the same blood much further, all around the body. Keeping the two circuits in separate chambers stops oxygen-poor and oxygen-rich blood from mixing.
Because it has the harder job. The right ventricle only pushes blood to the nearby lungs, but the left ventricle must drive blood through the entire body, so it needs a much stronger muscular wall.
They act as one-way doors. Each valve opens to let blood through, then closes so blood cannot flow backwards. That keeps every heartbeat pushing blood in one direction only.
No. It is a heavily simplified educational model of the heart's chambers and flow. It is not a medical diagnosis or clinical guidance — seek a professional physician for any health-related question.
A beat is the two atria contracting first to top up the ventricles, then both ventricles contracting together to push blood out to the lungs and the body, followed by a short rest.