The heart is a cone-shaped muscular "pump", lying in the center of the chest, with its apex pointing to the left and downward.

The heart is divided by muscle into left and right sides, each side has two chambers, the atrium (upper) and the ventricle (lower). Valves between the chambers allow a single-direction blood flow. This allows oxygenated blood supply to the whole body via the aorta.

 De-oxygenated blood

 Oxygenated blood