THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -A typical heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of the heart.

Detailed explanation-2: -The upper two chambers are called atria (singular: atrium) and the lower two are known as ventricles (singular: ventricle). Muscular walls, called septa or septum, divide the heart into two sides. On the right side of the heart, the right atrium and ventricle work to pump oxygen-poor blood to the lungs.

Detailed explanation-3: -The top chambers of the heart are called the left atrium and right atrium. The bottom chambers of the heart are the left ventricle and right ventricle, which have thicker walls.

Detailed explanation-4: -In humans the atria are the two upper chambers of the heart. Each is roughly cube-shaped except for an ear-shaped projection called an auricle. (The term auricle has also been applied, incorrectly, to the entire atrium.)