Heart External Anatomy: Surfaces, Borders, Great Vessels, and Coronary Landmarks

External Features You Can Identify at a Glance

Apex

The apex is the pointed tip of the heart. Externally, it is formed mostly by the left ventricle. In an intact specimen or 3D model, the apex points inferiorly, anteriorly, and toward the left. A practical way to remember it: the apex is the “tip” you would follow if you traced the heart down to its most narrow, pointed end.

Base

The base is the broad, relatively flat posterior aspect of the heart. Externally, it is formed primarily by the left atrium (with contribution from the right atrium). The base is where you will see the pulmonary veins entering (think: “back of the heart receives oxygenated blood”). On a model, rotate the heart so you are looking at its posterior side; the base is the “top-back platform” where several vessels attach.

Borders (Right and Left)

Borders are the outer contours you see when viewing the heart from the front or side.

• Right border: formed mainly by the right atrium. It appears more vertical and is often where the superior and inferior vena cava align as they enter the right atrium.
• Left border: formed mainly by the left ventricle (with a small contribution from the left auricle). It appears more oblique and rounds down toward the apex.

Surfaces (Anterior and Inferior)

Surfaces are named by what they face.

• Anterior (sternocostal) surface: the front-facing surface. It is formed mostly by the right ventricle, with contributions from the right atrium and left ventricle. On this surface you can often appreciate the anterior interventricular sulcus running toward the apex.
• Inferior (diaphragmatic) surface: the bottom surface that rests on the diaphragm. It is formed mostly by the left ventricle with a significant contribution from the right ventricle. On this surface you can often find the posterior interventricular sulcus.

Practical visualization tip: If you set a heart model on a table as if it were “resting,” the surface touching the table is the inferior (diaphragmatic) surface; the surface facing you is largely the anterior (sternocostal) surface.

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Great Vessels as They Appear Externally

When you look at the heart externally, the great vessels are easiest to identify by their size, position, and direction of travel. Use the “outflow vs inflow” approach: arteries leave the heart; veins enter it.

Aorta

The aorta is the large, thick-walled artery leaving the left ventricle. Externally, you typically see the ascending aorta emerging from the superior aspect of the heart and curving into the arch (depending on how much of the vessel is included in the model/specimen). It sits posterior to the pulmonary trunk at its origin in many views, but becomes prominent as it ascends.

Pulmonary Trunk

The pulmonary trunk leaves the right ventricle and courses superiorly before dividing into right and left pulmonary arteries. On the anterior view, it is often the most obvious large vessel arising from the heart’s superior aspect, positioned more anteriorly than the ascending aorta near their origins.

Superior Vena Cava (SVC)

The superior vena cava enters the right atrium from above. Externally, it appears as a large vein on the right side of the superior heart, often aligned with the right border. On a model, follow it down into the right atrium to confirm identification.

Inferior Vena Cava (IVC)

The inferior vena cava enters the right atrium from below. Externally, it is best appreciated when viewing the heart from an inferior or posterior angle. It is a key landmark for orienting the diaphragmatic surface and the right atrium’s inferior aspect.

Pulmonary Veins

The pulmonary veins (typically four) enter the left atrium on the posterior side of the heart. Externally, they are most clearly seen when you rotate to the base/posterior view. They are shorter vessels that appear to “plug into” the left atrium rather than travel a long distance along the heart’s surface.

External Grooves and Coronary Landmarks: The “Roadmap” on the Surface

The heart’s surface has grooves (sulci) that mark internal boundaries and serve as pathways where major coronary vessels typically run. Learning these grooves is like learning the main roads on a map: once you know them, you can predict where the vessels travel.

Coronary Sulcus (Atrioventricular Groove)

The coronary sulcus encircles the heart like a crown, separating the atria (above) from the ventricles (below). On an anterior view, it runs horizontally-ish beneath the atrial appendages and continues around to the posterior side.

What typically runs here: major coronary arteries and veins course within or near this groove. A key venous landmark associated with the posterior part of this groove is the coronary sinus (a large venous channel on the posterior side that collects cardiac venous blood).

Anterior Interventricular Sulcus

The anterior interventricular sulcus is a vertical groove on the anterior surface running toward the apex. It marks the external boundary between the right and left ventricles on the front of the heart.

What typically runs here: the anterior interventricular artery (commonly called the LAD, a branch of the left coronary artery) and the great cardiac vein often travel together in this sulcus toward the apex.

Posterior Interventricular Sulcus

The posterior interventricular sulcus is the corresponding groove on the diaphragmatic/posterior aspect of the heart, also running toward the apex. It marks the external boundary between the ventricles on the back/inferior side.

What typically runs here: the posterior interventricular artery (often called the PDA) and the middle cardiac vein commonly run in this sulcus.

How to Use Grooves to Predict Vessel Locations

• If you find the coronary sulcus, you are on the “ring road” between atria and ventricles; expect major coronary vessels and (posteriorly) the coronary sinus.
• If you find an interventricular sulcus, you are on the “divider road” between ventricles; expect an interventricular artery paired with a cardiac vein.
• If you can trace a sulcus to the apex, you are likely following an interventricular pathway (anterior or posterior).

Structured Palpation/Visualization Exercise (3D Model): Trace Grooves and Match Vessels

Use a rotatable 3D heart model (or a physical model) and follow this sequence. Your goal is to (1) trace each groove with your finger or cursor and (2) name the vessels that typically run within it.

Step 1: Set Orientation and Find the Apex

1. Rotate the model to an anterior view (you should see the pulmonary trunk and much of the right ventricle).
2. Locate the apex (the pointed inferior tip). Keep it in view; it will be your anchor point.

Step 2: Trace the Anterior Interventricular Sulcus to the Apex

1. From the anterior view, look for a groove running down toward the apex: the anterior interventricular sulcus.
2. Trace it with your finger/cursor from superior to inferior until you reach the apex.
3. Say out loud (or label on-screen): Anterior interventricular sulcus → LAD (anterior interventricular artery) + great cardiac vein.

Step 3: Find the Coronary Sulcus (Atrioventricular Groove) Like a Belt

1. Return to the anterior view and identify the boundary between atria and ventricles.
2. Trace the coronary sulcus laterally (toward the left border) and then continue around the right side as far as the model allows.
3. Rotate posteriorly while keeping your tracing path continuous, as if following a belt around the heart.
4. On the posterior side, identify the enlarged venous channel in this region (when visible): coronary sinus.
5. State the association: Coronary sulcus → major coronary vessels; posteriorly includes coronary sinus.

Step 4: Rotate to the Inferior/Posterior View and Trace the Posterior Interventricular Sulcus

1. Rotate the model so the diaphragmatic (inferior) surface is visible.
2. Find the groove running toward the apex on this side: the posterior interventricular sulcus.
3. Trace it toward the apex.
4. Match vessels: Posterior interventricular sulcus → PDA (posterior interventricular artery) + middle cardiac vein.

Step 5: Cross-Check Using Great Vessels and the Base

1. Rotate to the posterior view and identify the base (broad posterior aspect).
2. Locate the pulmonary veins entering the left atrium.
3. On the right side, identify the SVC entering from above and the IVC entering from below into the right atrium.
4. Return to the anterior-superior view and identify the pulmonary trunk and ascending aorta.
5. Use these as fixed landmarks to re-orient yourself if you get lost: vessels at the top, apex at the bottom tip, base at the back.

Quick Self-Test (No Labels)

Hide labels on the model (if possible) and answer these prompts:

• Point to the apex and name which chamber forms it.
• Point to the base and name which chamber forms most of it.
• Trace the coronary sulcus and name one major venous structure associated with its posterior portion.
• Trace the anterior interventricular sulcus and name the typical artery and vein found there.
• Trace the posterior interventricular sulcus and name the typical artery and vein found there.