Veins of The Heart

Most of the veins of the heart drains the oxygen-poor blood into a reservoir which is called coronary sinus. The coronary sinus lies in the left posterior portion of the atrioventricular groove, measuring between 2 and 3 cm in length. Being a continuation of the great cardiac vein, it receives deoxygenated blood from the oblique vein of the left atrium, the posterior vein of the left ventricle, as well as from the middle cardiac and the small cardiac vein. Finally, the coronary sinus empties all this returning blood from the heart tissue into the right atrium, with the blood flowing through the valve of the coronary sinus.

The great cardiac vein begins on the anterior surface of the apex of the heart, having as tributaries the veins of the anterior wall of both ventricles. Running up obliquely to the atrioventricular groove, it fits into it. When it reaches the diaphragmatic part of the atrioventricular groove, it widens to become the coronary sinus. The oblique vein of the left atrium arises on the lateral wall of the left atrium and then it runs down from left to right as a small branch in a fold in the pericardium; descending to the right, it then empties into the coronary sinus.

The anterior cardiac veins are not tributaries of the coronary sinus. Running obliquely upwards across the anterior-lateral surface of the right ventricle of the heart, they drain the oxygen-poor blood directly into the right ventricle.

Below, anterior side of heart, showing its veins and arteries.

Below, the posterior aspect of heart, showing the great cardiac veins, as it turns around the left lateral border of this organ, and the coronary sinus, with the tributary veins.

Great Cardiac Vein

The great cardiac vein is a large blood vessel which drains a vast area of anterior aspect of heart, which includes the left and right ventricle and left atrium. It begins on the anterior surface of apex of the heart. Then it runs up in the anterior interventricular groove, parallel to the anterior interventricular branch of left coronary artery. When it reaches the atrioventricular groove, it turns left, running alongside the circumflex branch of left coronary artery in the atrioventricular groove.

As it winds around the left border of the heart, the great cardiac vein travels in the posterior portion of the atrioventricular groove, ending up in the coronary sinus. Along its course, the great cardiac vein receives deoxygenated blood from important tributary branches, which contribute to drain about 65% of the heart. The coronary sinus is basically the dilated final portion of the great cardiac vein, receiving deoxygenated blood from the middle cardiac and the small cardiac vein as it empties into the right atrium.

Below, the great cardiac vein on anterior side of heart

Posterior aspect.

Cardiovascular System

The cardiovascular system consists of a network of arteries and veins, the blood that circulates through them, and the heart, which pumps the blood to every body tissue and organ through the arteries and arterioles. Its function is to sustain life, keeping all the tissue cells and organs alive by providing them with oxygen and nutrients. Oxygen is picked up by the red blood cells in the lung alveoli and the nutrients are absorbed from the small intestine, traveling to the liver through the superior mesenteric and portal vein.

Heart

The heart is the hub of the cardiovascular system. It is a muscular organ which contains four cavities: two atria and two ventricles. It is divided into two halves; the right side and the left side. The right half is composed of the right atrium and the right ventricle, which are connected through the tricuspid valve; running through the cava vein, oxygen-poor blood flows into the right atrium, from which it pours into the right ventricle. Both cavities of the right side are not communicated with those of the left side. Flowing from the lungs through the pulmonary veins, oxygen-rich blood pours into the left atrium, from which it runs into the left ventricle through the mitral valve. When the heart contracts, both ventricles pumps the blood to the organs, with the right ventricle sending the oxygen-poor blood to the lungs and the left ventricle ejecting oxygen-rich blood to every tissue and organ through the aorta and its arterial branches.

Blood Vessels

Arteries, arterioles, vein, venules, and capillaries make up the network of blood vessels through which the blood carries oxygenated blood and brings deoxygenated blood to and from the body tissues and organs. Arteries and arterioles (tiny arteries) convey oxygen rich blood from the left ventricle to every cells and organs in the body. Veins and venules (tiny veins) returns oxygen-poor blood, containing carbon dioxide (CO2), to the right atrium, to be sent to the lungs where CO2 is exhaled. Meanwhile, capillaries are the smallest blood vessels, constituting the vascular bridge that links up the arteries with the veins.

In the lungs alveoli, venous blood releases the CO2 and then is saturated with oxygen. Then it returns to the left atrium through the pulmonary veins. The pulmonary vein is the only vein in the body that carries oxygenated blood, as it lies between the heart and the lungs, while the pulmonary artery is the only artery of the body which carries venous (deoxygenated) blood.

Below, diagram of cardiovascular system

Coronary Arteries

The coronary arteries are the two blood vessels which supply the heart with oxygenated blood. There is a left and a right coronary artery and they are the first branches of the aorta. Each of them arises from the corresponding left and right aortic sinus, which is one of the dilated parts at the base of the ascending aorta above each one of the cusp of the aortic valve.

The left coronary artery originates from the left aortic sinus and descends obliquely, giving off its two main branches; the anterior interventricular artery, which travels all the way down to reach the apex of heart, and the circumflex artery, which curves to the left in the atrioventricular groove, winding around the border of heart to the posterior side of this organ.

The right coronary artery arises from the right aortic sinus and runs around to the right side of heart along the atrioventricular groove, giving off branches that supply both the right atrium and ventricle. On the posterior side of heart, it gives off the posterior interventricular branch. You have to bear in mind that the right coronary has less side branches and blood volume than the left coronary artery.

Anterior aspect of human heart, showing the two coronary arteries.

 

Right Coronary Artery

The right coronary artery supplies the right side of the heart with oxygenated blood. It arises from the right aortic sinus, at the base of the aorta. Then it travels obliquely down towards the right in the atrioventricular groove, between the conus arteriosus of right atrium and the right auricle of right atrium.

When it reaches the right border of the heart, the right coronary artery gives off the right marginal branch, which descends towards the apex of heart and anastomoses with branches of the anterior interventricular artery. Having given off some branches to the right atrium and ventricle, it winds around to the postero-inferior surface of heart, or diaphragmatic side.

Before it reaches the middle of the diaphragmatic side, it sends the posterior interventricular branch, which descends to the apex of heart. Then it keeps running in the groove, giving off secondary branches that penetrate deeply into the myocardium.

Below, anterior view of heart, showing the left and right coronary artery

Below, posterior side of heart, exhibiting the circumflex artery (a branch of the left coronary) and the posterior interventricular branch of the right coronary artery.

 

Left Coronary Artery

The left coronary artery is a one of the two main blood vessels that supply the heart with oxygenated blood. It is larger than the right coronary, with more side branches, carrying more blood volume. Supplying a large area of the myocardium, it is in one of its branches where most of the heart coronary occlusion occurs.

The left coronary artery originates from the left sinus of Valsalva (left aortic sinus), which is just above the left cusp of the aortic valve. It runs to the left, behind the root of the pulmonary trunk and then between the pulmonary trunk and the auricle of the left atrium. When it is about to reach the left half of the atrioventricular groove, the left coronary artery divides into two important branches; the anterior interventricular and the circumflex branch.

The anterior interventricular branch (also called left anterior descending artery) runs all the way down along the anterior interventricular groove on anterior side of heart, reaching the apex of heart. Along the way, it sends secondary side branches, such as the diagonal branch. Meanwhile, the circumflex artery turns left, gives off the left marginal branch and keeps traveling sideways, winding around the heart in the atrioventricular groove to the posterior side of this organ where it descends across its posterior surface.

Below, image of anterior aspect of heart, showing the left coronary artery and its branches.

 

Circumflex Artery

The circumflex artery is one of the two main blood vessels into which the left coronary artery bifurcates. From its point of origin, it begins to descend obliquely towards the left, right below the auricle of left atrium. Then it levels off and keeps running to the left in the atrioventricular groove, giving off the left marginal branch. Extending along this narrow depression, the circumflex artery winds around towards the posterior side of heart, parallel and side by side with the great cardiac vein.

Before it reaches the middle line of heart posterior aspect, the circumflex artery gives off an important ascending branch that supplies the posterior side of left atrium and its auricle. Then it travels downwards onto the diaphragmatic surface of heart. However, it does not reach the apex of this organ.

The function of this circumflex branch of the left coronary artery is to supply a large area of the heart, which comprises the left atrium and its auricle as well as the posterior part of left ventricle.

Below, anterior view of heart, showing the point of emergence of the circumflex artery.

Posterior view of heart, exhibiting the same artery as it takes a dive downwards towards the apex.

 

Anterior Interventricular Artery

The anterior interventricular artery is one of the two main branches into which the left coronary artery divides, the other being the circumflex branch. It is also known as the left anterior descending artery. It is in the lumen of this blood vessel and its side branches where most of coronary artery occlusions occur, causing heart attack.

The anterior interventricular artery arises from the left coronary. Then it descends almost vertically along the anterior interventricular groove as it runs down all the way to the apex of the heart, arching over it. Next, it enters the terminal part of the inferior interventricular groove, penetrating deep into the myocardium.

Along its course, the anterior interventricular artery first sends secondary branches to the infundibulum (conus arteriosus), which is the anterosuperior portion of right ventricle. Then, as it keeps traveling downwards, it gives off the diagonal branch, which runs obliquely downwards across the left ventricle, as well as other smaller branches to the nearest areas of the right and left ventricle. The branches extending over the left ventricle are longer, with more offshoots, than those on the right.

Function: it supplies all the parts and tissues that make up the heart (myocardium, epicardium, endocardium, pericardium, and other structures).

Below, the human heart, with its arterial vessels. The anterior interventricular artery is clearly labeled.