Coronary Circulation

The blood supply to the heart muscle is furnished mainly by the coronary arteries, which originate from the aorta immediately after the aortic valve. These vessels pass through the fatty tissue beneath the pericardium and then branch out into the heart muscle. Deoxygenated blood is transported from the heart muscle to the right atrium by the coronary veins. The heart's energy supply is almost completely dependent on the coronary vessels. Only the tissues lying directly beneath the endocardium receive a sufficient amount of oxygen from the blood within the cavities of the heart.

The coronary arteries do not have any effective collateral circulation. That is, each part of the heart depends on its own coronary branch for its blood supply. If a branch becomes particularly or completely blocked through various heart diseases, the result can be a heart attack or lesser muscle damage. Spasms in the wall muscles of the coronary arteries can also result in obstruction that impede the flow of blood.

Heart Hormone
Like a member of other internal organs, the heart produces a hormone with regulatory effects on other body systems. The heart hormone is called atrial natriuretic factor. The name refer to its origin in the atria and its contributory role in maintaining proper the excessive loss of sodium and other cations in urine. Atrial natriuretic factor also has a strong hypotensive, or lowering, effect on blood pressure and of aldosterone by the adrenal cortex. These and other hormonal and neutral mechanisms all interact with one another in the control of salt and water levels in the body.