The human heart is a muscular organ about the dimensions of a fist, located just behind and slightly left of the breastbone. The human heart pumps blood through the network of arteries and veins called the circulatory system . Heart circulates blood throught out the body.
The human heart has four chambers. The human heart right atrium of the heart receives blood from the veins and pumps it to the proper ventricle. The human heart ventricle receives blood from the proper atrium and pumps it to the lungs, where it's loaded with oxygen.The left atrium of the heart receives oxygenated blood from the lungs and pumps it to the ventricle. The coronary arteries line the surface of the guts and supply oxygen-rich blood to the guts muscle. an internet of nervous tissue also runs through the guts , conducting the complex signals that govern contraction and relaxation. Surrounding the guts may be a sac called the pericardium.