The internal partitions divide the heart into four chambers creating grooves that appear on its outer surface. They are known as the external sulci of the heart, and they include the following:

Coronary (atrioventricular) sulcus
Interventricular sulci
- Anterior interventricular sulcus
- Posterior interventricular sulcus

The coronary sulcus encircles the heart, marking the separation between the atria and ventricles. Therefore, it is also called the atrioventricular sulcus. It houses the right coronary artery (RCA), left circumflex artery (LCx), coronary sinus and small cardiac vein (may be absent).

In contrast, the interventricular sulci represent the separation of both ventricles. They contain various vessels and adipose tissue.

The anterior interventricular sulcus is located on the sternocostal surface. It contains the left anterior descending artery (LAD) and anterior interventricular vein (portion of the great cardiac vein).

The posterior interventricular sulcus is found on the diaphragmatic surface. It houses the posterior descending artery (PDA) and middle cardiac vein (posterior interventricular vein).

Note: The coronary sulcus meets the posterior interventricular sulcus at the site called the crux of the heart or cardiac crux. It can be found on the posteroinferior aspect of the heart.

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External sulci of heart