QS Study

The coronary sinus is the venous sinus draining most of the heart. It collects the majority of the cardiac venous blood. It returns the majority of the left ventricular blood flow to the right atrium.


It lies in that part of the posterior atrioventricular groove between the left atrium & left ventricle. This system is conscientious for draining the internal layers of the myocardium of the right ventricular venous system and portions of the interventricular septum directly into the right ventricle via orifices that are often, 0.5 mm in diameter. It is present in all mammals, including humans.


To the right: It ends in the right atrium.

To the left: Anatomically it is continuous with great cardiac vein but embryologically continuous with the oblique vein of the left atrium.

End: It ends in the right atrium between the opening of the inferior vena cava & right atrioventricular orifice.

Fig: Coronary Sinus


The end of the sinus is guarded by a semilunar valve, called the valve of the coronary sinus, which is continuous with the valve of inferior vena cava. The right venous valve of the sinus venous develops into the thebesian valve and the Eustachian valve.


The coronary sinus develops from one of the two sinus horns of the sinus venosum. It develops from the left horn of sinus venosus. It receives blood mainly from the small, middle, great and oblique cardiac veins. It also plays an important role in many other heart procedures.

Tributaries: are –

  1. Great cardiac vein.
  2. Middle cardiac vein.
  3. Posterior vein of the left ventricle.
  4. Oblique vein of the left atrium.
  5. Right marginal vein.
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