The heart is a muscular double pump: its right side sends oxygen-poor blood to the lungs, while its left side sends oxygen-rich blood to the body.
The four chambers and their jobs
The upper chambers are the right and left atria; they mainly receive blood. The lower chambers are the right and left ventricles; they pump blood out. A muscular wall called the septum helps keep oxygen-poor blood on the right from mixing with oxygen-rich blood on the left.
Follow one complete blood journey
Blood from the body enters the right atrium through the venae cavae, moves to the right ventricle and travels through the pulmonary artery to the lungs. After collecting oxygen, it returns through pulmonary veins to the left atrium, enters the left ventricle and is pushed through the aorta to the body.
What valves and lub-dub do
Four valves keep blood moving mainly in one direction. The familiar heart sounds are linked chiefly to valves closing: the first sound follows closure of the atrioventricular valves, and the second follows closure of the aortic and pulmonary valves.
Why the left ventricle is thicker
The right ventricle pumps only to the nearby lungs. The left ventricle must generate enough pressure to send blood through the entire body, so its muscular wall is much thicker. This structure-function link is a common Class 10 and NEET question.
Concept Map
Fast facts
| Chambers | Right atrium, right ventricle, left atrium, left ventricle. |
| To lungs | Pulmonary artery carries oxygen-poor blood. |
| From lungs | Pulmonary veins carry oxygen-rich blood. |
| To body | The aorta distributes oxygen-rich blood. |
| Sources | US National Heart, Lung, and Blood Institute and NCBI cardiac physiology overview |
Did you know?
The pulmonary artery and pulmonary veins are named by the direction blood travels relative to the heart, not by whether the blood is rich in oxygen.
Watch the short here: open the YouTube explanation.
Key takeaway
Memorise the pathway as body -> right heart -> lungs -> left heart -> body. Valves prevent backflow, and the thick left ventricle supplies the pressure for systemic circulation.
