Left coronary artery

Where does the left coronary artery start?

It arises from the left aortic sinus, one of three slight dilations in the wall of the aorta opposite the cusps of the aortic valve. The right sinus gives rise to the right coronary artery, and these two coronary arteries are the only branches of the ascending aorta. (OpenStax A&P 2e, 19.1; Gray 1918, 4b. The Heart and 2. The Aorta; StatPearls, Cardiac Muscle)

From the aorta it runs along the coronary sulcus, the deep groove between the atria and the ventricles. (StatPearls, Heart Arteries; OpenStax A&P 2e, 19.1)

What are the branches of the left coronary artery?

It is also called the left main coronary artery, and it is short. It divides into the circumflex artery, which follows the coronary sulcus to the left, and the larger anterior interventricular artery, also called the left anterior descending artery (LAD). (StatPearls, Heart Left Anterior Descending Artery and Heart; OpenStax A&P 2e, 19.1)

What does the left coronary artery supply?

Its anterior interventricular branch is the main supply to the front wall of the left ventricle and to most of the interventricular septum. The circumflex and its branches supply the posterolateral part of the left ventricle. (StatPearls, Heart Left Anterior Descending Artery and Heart Arteries)

Flow through the coronary arteries peaks while the heart muscle relaxes and drops close to zero while it contracts, because the contracting muscle squeezes the small branches that run into it. (OpenStax A&P 2e, 19.1; StatPearls, Heart Left Anterior Descending Artery)

Where does the left coronary artery meet other vessels?

Its branches join those of the right coronary artery in three places. The anterior interventricular artery meets the posterior interventricular artery near the apex, the circumflex meets the right coronary artery in the coronary sulcus, and septal branches of both meet inside the interventricular septum. (StatPearls, Heart Arteries and Heart Left Anterior Descending Artery)

These connections are few, and the coronary arteries are treated as end arteries, so a blocked one often leads to the death of the heart muscle cells it supplies, a myocardial infarction. (OpenStax A&P 2e, 19.1; StatPearls, Heart Arteries)

The great cardiac vein runs beside the anterior interventricular branch and drains blood from both ventricles and the left atrium. (OpenStax A&P 2e, 19.1; StatPearls, Heart Veins)

Does the left coronary artery vary between people?

In some people the left main coronary artery is absent. The anterior interventricular and circumflex arteries then leave the aorta through one shared opening, or through two separate openings in the left aortic sinus. (StatPearls, Heart Left Anterior Descending Artery)

In about 10% of hearts, by the StatPearls article on the heart arteries, the left coronary artery gives rise to the posterior interventricular artery, which makes the heart left dominant. (StatPearls, Heart Arteries)

Where the sources differ

The sources name the aortic sinuses differently. OpenStax says the left coronary artery arises from the left posterior aortic sinus and the right from the anterior aortic sinus. The StatPearls article on the anterior descending artery places them in the left anterior and the right anterior aortic sinus, and the StatPearls article on cardiac muscle calls them the left and the right aortic sinus. (OpenStax A&P 2e, 19.1; StatPearls, Heart Left Anterior Descending Artery and Cardiac Muscle)