Coronary sinus

The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). It delivers less-oxygenated blood to the right atrium, as do the superior and inferior venae cavae. It is present in all mammals, including humans.Diagram showing completion of development of the parietal veins.Posterior view of coronary circulation The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). It delivers less-oxygenated blood to the right atrium, as do the superior and inferior venae cavae. It is present in all mammals, including humans. The name comes from the Latin corona, meaning crown, since this vessel forms a partial circle around the heart. The coronary sinus drains into the right atrium, at the coronary sinus orifice, an opening between the inferior vena cava and the right atrioventricular orifice or tricuspid valve. It returns blood from the heart muscle, and is protected by a semicircular fold of the lining membrane of the auricle, the valve of coronary sinus (or valve of Thebesius). The sinus, before entering the atrium, is considerably dilated - nearly to the size of the end of the little finger. Its wall is partly muscular, and at its junction with the great cardiac vein is somewhat constricted and furnished with a valve, known as the valve of Vieussens consisting of two unequal segments. The coronary sinus starts at the junction of the great cardiac vein and the oblique vein of the left atrium. The end of the great cardiac vein and the coronary sinus is marked by the Vieussens valve.