Direction

Forwards, upwards, slightly left.

Formation (4 chambers)

Left atrium not visible — hidden behind ascending aorta + pulmonary trunk

Grooves

Anterior coronary sulcus (AV groove) — separates right atrium (above) from right ventricle (below); interrupted by infundibulum; contains right coronary artery

Anterior interventricular groove — pulmonary trunk root to apex; separates RV (right) from LV (left); contains LAD + great cardiac vein

Infundibulum (Conus Arteriosus)

• Smooth, cone-shaped RV outflow tract → pulmonary valve/trunk
• From bulbus cordis developmentally
• Interrupts anterior coronary sulcus

Structures Visible — Upper Part (Right→Left)

1. SVC
2. Ascending aorta
3. Pulmonary trunk
4. Right auricle (overlaps ascending aorta root)
5. Left auricle (projects from behind pulmonary trunk)

Anterior Relations

• Sternum + costal cartilages 2–6
• Anterior borders of both lungs/pleura
• Thymus remnant
• Anterior mediastinum

Area of Superficial Cardiac Dullness

• Cardiac notch of left lung leaves triangular area uncovered, behind left 4th/5th costal cartilages
• Only pericardium separates chest wall from right ventricle here
• Percussion → dullness
• Loss of dullness → emphysema or left pneumothorax (lung overexpands into costomediastinal recess)

Applied Anatomy

• LAD occlusion → anterior MI (most extensive pattern) — LAD supplies anterior LV wall, anterior 2/3 IVS, apex
• Pericardiocentesis — uses superficial cardiac dullness area; left 5th ICS near sternum, or subxiphoid route — avoids lung

Direction

Faces forwards, upwards, and slightly to the left.

Formation

Formed by four chambers — mainly the right atrium and right ventricle; partly the left auricle and left ventricle.

Left atrium is not visible — hidden behind the ascending aorta and pulmonary trunk.

Grooves on the Surface

Anterior Coronary Sulcus (AV Groove)

• Separates right atrium (above) from right ventricle (below)
• Interrupted in the middle by the infundibulum (conus arteriosus)
• Contains: right coronary artery

Anterior Interventricular Groove

• Runs from root of pulmonary trunk to apex
• Separates right ventricle (right) from left ventricle (left)
• Contains: anterior interventricular artery (LAD) + great cardiac vein

Infundibulum (Conus Arteriosus)

Smooth, cone-shaped outflow tract of the right ventricle, projecting upwards and to the left towards the pulmonary valve and pulmonary trunk. Its smooth wall is developmentally derived from the bulbus cordis. Interrupts the anterior coronary sulcus.

Structures Visible — Upper Part (Right → Left)

1. Superior vena cava
2. Ascending aorta
3. Pulmonary trunk
4. Right auricle (overlaps root of ascending aorta)
5. Left auricle (projects from behind pulmonary trunk)

Anterior Relations (What Covers This Surface)

• Sternum and costal cartilages 2–6
• Anterior borders of both lungs and pleura
• Thymus remnant (fibrofatty tissue in adults)
• Anterior mediastinum

Area of Superficial Cardiac Dullness

The cardiac notch of the left lung leaves a triangular area of the sternocostal surface uncovered by lung — directly behind the left 4th and 5th costal cartilages. Only pericardium separates the chest wall from the right ventricle here.

Percussion → dullness = area of superficial cardiac dullness.

Loss of this area suggests emphysema or left pneumothorax (lung overexpands into costomediastinal recess).

Clinical Correlation

LAD occlusion: Occlusion of the anterior interventricular artery causes anterior MI — the most extensive pattern, as the LAD supplies the anterior wall of the left ventricle, anterior two-thirds of the interventricular septum, and the apex.

Pericardiocentesis: The uncovered area (superficial cardiac dullness) is used for needle access to the pericardial sac — either via the left 5th intercostal space adjacent to the sternum, or via the subxiphoid route — avoiding lung.

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