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.
|Source||Great cardiac vein|
|Drains to||Right atrium|
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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 junction of the great cardiac vein and the coronary sinus is marked by the Vieussens valve. It is present in 65% to 87% of the population. The coronary sinus runs transversely in the left atrioventricular groove on the posterior aspect of the heart. The coronary sinus then drains into the posterior wall of right atrium. The orifice of the coronary sinus is located to the left of the orifice of inferior vena cava in the right atrium.
The valve of the coronary sinus (also known as "Thebesian valve" is a thin, semilunar (half moon shape) valve located on the anteroinferior part of the opening into the right atrium. It is present in 73% to 86% of autopsied heart.
The coronary sinus receives blood mainly from the small, middle, great and oblique cardiac veins. It also receives blood from the left marginal vein and the left posterior ventricular vein. It drains into the right atrium.
The anterior cardiac veins do not drain into the coronary sinus but drain directly into the right atrium. Some small veins known as Thebesian veins drain directly into any of the four chambers of the heart.
Electrodes can be inserted into and through the coronary sinus to study the electrophysiology of the heart. This includes for a coronary sinus electrogram. The coronary sinus connects directly with the right atrium. It will dilate as a result of any condition that causes elevated right atrial pressure, such as pulmonary hypertension. Dilated coronary sinus is also seen in some congenital cardiovascular conditions, such as persistent left supervisor cava, and total anomalous pulmonary venous return.
Diagram showing completion of development of the parietal veins.
Posterior view of coronary circulation