Heart External Surface Organization

Heart External Surface Organization is the description of the surfaces, borders, sulci, and external landmarks visible on the outer aspect of the intact heart, encompassing the named surfaces formed by each chamber's external contour, the grooves marking the boundaries between chambers and containing the coronary vasculature, and the overall external contour features used to orient the heart in anatomical and imaging contexts.

The Named Surfaces of the Heart

The Sternocostal (Anterior) Surface

The sternocostal surface, facing anteriorly toward the sternum and costal cartilages, is formed predominantly by the right ventricle, with a smaller contribution from the right atrium along its right border and a narrow strip of left ventricle along its left border, making the right ventricle the chamber most directly encountered when approaching the heart from its anterior aspect.

The Diaphragmatic (Inferior) Surface

The diaphragmatic surface, resting upon the central tendon of the diaphragm, is formed predominantly by the left ventricle, with a smaller contribution from the right ventricle, and represents the inferior aspect of the heart that maintains direct contact with the diaphragmatic muscle below.

The Pulmonary (Left) Surfaces

The left and right pulmonary surfaces of the heart, facing toward each respective lung and forming the cardiac impression upon the medial surface of each lung, are formed predominantly by the left ventricle on the left side and the right atrium on the right side.

The Base (Posterior Surface)

The base of the heart, oriented posteriorly, is formed predominantly by the left atrium, with a contribution from the right atrium, and represents the surface at which the pulmonary veins enter from behind and through which the heart maintains its close posterior relationship to the esophagus.

Cardiac Borders

The Right Border

The right border of the heart, formed by the right atrium, extends in a gently curved vertical line between the superior and inferior venae cavae, representing the rightmost extent of the cardiac silhouette as typically visualized on frontal chest imaging.

The Left Border

The left border of the heart, formed predominantly by the left ventricle with a smaller superior contribution from the left auricle, extends from the pulmonary trunk region down toward the cardiac apex, representing the leftmost extent of the cardiac silhouette.

The Inferior Border

The inferior border of the heart, formed predominantly by the right ventricle with a contribution from the left ventricle near the apex, extends nearly horizontally between the right border and the apex, closely following the line of the diaphragmatic surface.

Sulci and the Coronary Vasculature

The Coronary Sulcus

The coronary sulcus, also termed the atrioventricular groove, encircles the heart at the boundary between the atria superiorly and the ventricles inferiorly, marking the external landmark corresponding to the internal atrioventricular septal plane and providing the pathway along which the main coronary arteries and their major branches course.

The Interventricular Sulci

The anterior and posterior interventricular sulci mark the external boundary between the right and left ventricles on the sternocostal and diaphragmatic surfaces respectively, converging near the cardiac apex and providing the pathway along which the anterior and posterior interventricular coronary arterial branches course.

The Crux of the Heart

The point on the posterior surface of the heart at which the coronary sulcus and the posterior interventricular sulcus intersect, termed the crux of the heart, represents a significant anatomical landmark corresponding to the region where major coronary arterial branches typically converge and where the atrioventricular conduction node lies in close internal proximity.

The Auricles

Atrial Appendages

Each atrium possesses an external auricular appendage, a small, conical, muscular pouch projecting anteriorly from the main atrial body, with the right auricle projecting from the right atrium and the left auricle projecting from the left atrium, structures that increase overall atrial volume capacity and are visible as distinct external protrusions on the anterior cardiac surface.

Schematic External Surface Overview

Long-Term Significance

Heart External Surface Organization provides essential anatomical grounding for identifying and orienting cardiac structures from an external viewing perspective, establishing the named surfaces, borders, sulci, and auricular landmarks as foundational reference points for both anatomical dissection and the clinical interpretation of cardiac imaging and surgical approach.