Coronary Sinus Anatomy, Function & Definition

The coronary sinus is the place where smaller veins merge to form a large one serving the purpose of regulating blood circulation to the heart.

The coronary Sinus is generally located at the back of its left ventricle cavity and within close proximity to its left auricle, with which it’s interconnected via a small opening known as the ostium.

The size of the vein allows a lot of blood to be passed through without getting congested.

The cardiac venous blood is collected into the coronary sinus, which has an opening that leads into the right atrium.

The cardiac venous blood comes from the tissues of the myocardium (a thick layer of heart muscle) and collects in this cavity.

The organ is a passage that runs through the heart and with a little maneuvering can be used to tunnel into the heart in various ways.

Some doctors use it to repair damaged arteries while others open the coronary sinus up to get at such things such as tumors or enlarged hearts.

A lot of surgeons like using this particular passageway because it’s one of the few options they have when it comes to accessing the inside of your heart during certain procedures.

Consider, for example, the balloon catheter. This device can place contrasting agents and other therapies.

For coronary artery disease sufferers, though, whose surgery would normally damage their myocardium (heart muscle).

The coronary sinus may be an ideal location to deliver cardioplegia to protect this vital organ during surgery.

Cardioplegia is nicknamed the heart’s chill pill. Individuals requiring surgery may be advised to use cardioplegic solutions.

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Before attempts are made to keep their heart still throughout the process of the surgery so they stay protected both physically and mentally.

The Chambers of the coronary sinus is often guarded by a semi-circular endocardial valve, also known as the Thebesian valve.

Coronary Sinus

The function of this structure is similar to the tricuspid valve in that it prevents debris from entering into the heart chambers after it has already begun its journey through the venous system during diastole.

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This valve is generally present across the lower part of the atrioventricular orifice, although it may be absent, or cover no space at all.

More Details

The coronary sinus, found in the pit of the right atrium, is a significant landmark because it takes part in creating a triangle.

Marking the points where three important structures meet: the tricuspid valve, the inferior vena cava and caval opening, and the superior vena cava.

The coronary sinus collects the perfusion of the heart’s ventricles and pumps it back to both atria and into circulation.

The base is outlined by the Orifice of coronary sinus. The tendon of Todaro marks the superior pole, and the attachment of septal leaflet defines inferior pole of the triangle.


The coronary sinus is surrounded and protected by the heart muscle and it is where the venous blood drains into.

It bodes out from underneath the left atrium, which is one of four chambers of the human heart.

The coronary veins and the coronary sinus which carry blood and oxygen to and from the heart, respectively, are located in a chamber, called the left ventricle.

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This chamber is located on the left side of the heart.

The myocardium is a thick layer of tissue that fortifies each of these chambers of the heart as well as those muscles that help pump blood throughout the body as necessary.Coronary Sinus

Anatomical variations

The coronary sinus is essentially the root of the heart’s blood supply system. It’s not unusual for this vein to receive several different tributaries of veins throughout its length.

On occasion, there may be an example where these tributaries are more numerous than usual.

Or even rare occurrences of additional tributaries entering the smaller veins where they ultimately merge at the top of the heart with other examples.

The cardiac veins, like several other vessels in the human body, could at times find themselves somewhat obscured.

If the coronary sinus was not visible or perhaps even obliterated, then depending on the circumstances beneath this phenomenon.Coronary Sinus For example, if there were enough course of the blood through the heart, one would still be able to establish a direct connection with these flowing vessels.

Which would fill up into either side of the superior vena cava or through an additional passage that routes into both of the brachiocephalic veins.


The coronary sinus collects blood from the heart itself. In other words, it collects what is called cardiac venous blood.

It does this by way of coronary veins found throughout the muscle tissue of the heart.

The coronary sinus acts as the exit for deoxygenated blood that has been received from the Epicardial Ventricular Veins, which are vena cava veins of the heart muscle.

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The coronary sinus delivers this blood to the right atrium. This blood will then travel backward to the lungs where it mixes with oxygen once again before returning to the heart.

Frequently Asked Questions About Coronary Sinus

Where does the coronary sinus open?

The opening of the coronary sinus connects with the right atrium, between the inferior vena cava (IVC) and the tricuspid valve.

The opening of the coronary sinus allows blood from other arteries in the heart to return to other parts of the body through a semicircular valve, called a valve of Thebesius.

Do all veins drain into the coronary sinus?

The left atrium receives venous drainage from most epicardial veins, including the anterior interventricular vein, the right coronary vein, and the deep cardiac veins.

Where do coronary veins drain to?

Most veins are connected to the heart via the coronary vein. But there are exceptions.

Including right auricular, intercostal, subclavian, and sublingual veins all being connected to the heart via one of these three anomalous vessels:

The middle cardiac vein, an unpaired vessel on the left side; Sinus venosus, a blind-ended sinus within the conus arteriosus on the right; and to superior vena cava (notably at its union with the coronary sinus) on both sides.


Praise Adughele

I am a practising physician and medical expert also a blogger and content creator

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