Video narration
How can a four-room house send blood to both the lungs and the body without backflow? Outside, the heart sits inside the pericardium: base above, apex below. Auricles are outer flaps; great vessels connect there. In front view, anatomical right is on your left: right atrium above right ventricle; left atrium above left ventricle. A muscular septum divides the house, while thick walls pump. Trace the pipes: body, venae cavae, right atrium, right ventricle, pulmonary artery, lungs; pulmonary veins return blood to left atrium, left ventricle, and aorta sends it to the body. That is the key: right sends blood to lungs; left sends it to body. Pulmonary arteries carry deoxygenated blood, but pulmonary veins carry oxygenated blood. The tricuspid, mitral, pulmonary, and aortic valves are one-way doors. Chordae tendineae and papillary muscles support these valves. This four-room house separates the route; one-way valves stop backflow: lungs, then body.