the left ventricle. it has to pump against more pressure because it pumps blood to the entire body.
The heart is divided into 4 chambers: upper are the right and left atria, and the lower are the right and left ventricals.
1. Pulmonary veins 2. Left atrium 3. Right atrium 4. Aorta 5. Valves 6. Left ventricle 7. Right ventricle 8. Pulmonary Artery 9. Septum10. mitral valve11. bicuspid valve12. semi-lunar aortic valve13....
The 4 MAIN parts of the heart are the right atrium, left atrium, right ventricle and left ventricle.