The Anatomy of the Coronary Sinus

A group of veins that collect blood from the heart

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The coronary sinus is a group of veins that come together to comprise a large blood vessel, which functions to collect deoxygenated blood from the heart muscle. The coronary sinus is not the only vessel that delivers deoxygenated blood to the heart; the superior venae cavae and inferior venae cavae are other large vessels that do the same.

The coronary sinus is located on the heart’s posterior (behind) surface and is positioned between the left ventricle and the left atrium. All mammals, including humans, are known to have a coronary sinus.

Close look at the heart

Rasi Bhadramani / Getty Images


To understand the anatomy of the coronary sinus, it’s important to have some knowledge of how the blood travels through the heart.

The right and left sides of the heart work together to effectively circulate oxygen-rich blood throughout the body. The oxygen travels from large arteries (such as the aorta) to smaller arteries, then to small vessels called capillaries to supply cells, tissues, and organs.

There are four chambers of the heart, including two upper chambers—the right and left atrium—and two lower chambers—the right and left ventricles.

The heart/lung circulation of blood repeats itself continually, ensuring that blood is continuously flowing through the heart, lungs, and body.

The coronary sinus is big enough around to allow blood from most of the coronary veins to be deposited. Most of the cardiac veins collect blood and then return it to the heart via the right atrium and through the coronary sinus.

The coronary sinus receives the blood from the thick layer of muscle in the heart, called the myocardium; it goes on to facilitate the movement of the blood into the right atrium of the heart.   


The coronary sinus is a group of small veins that merge to form the sinus. It is located in the posterior (back) surface of the heart between the right and atria. The length of the coronary sinus is from 15 to 65 millimeters (0.59 to 2.5 inches).

Anatomical Variations

A congenital defect (present at birth) of the coronary sinus is called cardiac TAPVR, or cardiac total anomalous pulmonary venous return. This is a birth defect of the heart in which the baby’s oxygenated blood gets delivered to the wrong side of the heart.

This results in a shortage of adequate oxygen supply being delivered to the baby’s cells, organs, and tissues. The pulmonary veins (which should deliver oxygenated blood to the left atrium to eventually be pumped throughout the body), mistakenly connect to the right atrium.

Defect Involving the Coronary Sinus

If a baby is born with a congenital defect called cardiac TAPVR, the coronary sinus mistakenly helps connect the pulmonary veins to the right atrium—when they should travel to the left atrium.


The function of the coronary sinus is to serve as the primary collector of blood that has traveled from the heart, then eventually back to lungs to be oxygenated again; the coronary sinus collects what is called cardiac venous blood. This means it collects blood that needs to be reoxygenated from the cardiac (heart) veins.

The coronary sinus (which is a major vein of the human heart) receives drainage from other major veins in the heart, which are referred to as the “epicardial ventricular veins,” they include:

  • The great cardiac vein
  • The anterior interventricular veins
  • The left marginal vein
  • The posterior veins of the left ventricle
  • The posterior interventricular veins 

Clinical Significance

When heart surgery is performed, it is common that the surgeon enacts a procedure called cardioplegia. This involves deliberately stopping the heart (temporarily) during a surgical heart procedure.

The delivery of cardioplegia through the coronary sinus has been proven effective and safe in myocardial (the muscle of the heart) protection. It has even been found to be a better method of cardioplegia–compared to the traditional method—particularly for patients having heart surgery for coronary artery disease.

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  1. The University of Minnesota. Atlas of human cardiac anatomy. Comparative anatomy tutorial.

  2. Cleveland Clinic. How does the blood flow through your heart? Updated April 30, 2019.

  3. University of Minnesota. Atlas of human cardiac anatomy. Coronary sinus. Updated April 15, 2019.

  4. Centers for Disease Control and Prevention. Facts about total anomalous pulmonary venous return (TAPVR). Updated November 17, 2020.

  5. Gundry, S., Kirsh, M. A comparison of retrograde cardioplegia verses antegrade cardioplegia in the presence of coronary artery obstruction.