Topography of heart
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anatomy diagram topography of heart in middle mediastinum showing surfaces borders and relations
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Topography of the Heart
The heart lies in the middle mediastinum, enclosed by the pericardium. About two-thirds lies to the left of the median plane and one-third to the right.
- Axis: directed downward, forward, and to the left.
- Position: oblique, with the right ventricle forming most of the anterior surface.
- Apex: directed downward, forward, and leftward.
- Base: directed backward, upward, and rightward.
Surface projection
- Apex beat: normally in the left 5th intercostal space, about 2 cm medial to the midclavicular line.
- Right border: chiefly the right atrium; extends from the right 3rd costal cartilage to the right 6th costal cartilage, close to the right sternal margin.
- Left border: mainly the left ventricle, with a small contribution from the left auricle.
- Inferior border: mostly right ventricle, with a small left-ventricular part near the apex.
Color Atlas of Human Anatomy, Vol. 2: Internal Organs, pp. 70-71.
Surfaces
| Surface | Mainly formed by | Relations |
|---|---|---|
| Sternocostal (anterior) | Right ventricle, part of right atrium and left ventricle | Sternum, costal cartilages, anterior mediastinum, lungs and pleura |
| Diaphragmatic (inferior) | Mainly left ventricle, partly right ventricle | Central tendon of diaphragm; liver lies below the diaphragm |
| Right pulmonary surface | Right atrium | Right lung and mediastinal pleura |
| Left pulmonary surface | Mainly left ventricle | Left lung and mediastinal pleura |
Base and apex
- Base (posterior surface): predominantly the left atrium, with a smaller right atrial contribution. It is related to the esophagus, descending thoracic aorta, and vertebral column.
- Apex: formed by the left ventricle. It is located behind the left 5th intercostal space and produces the apex beat.
Important relations
Anteriorly
- Sternum and left costal cartilages
- Anterior borders of lungs and pleura
- Pericardium
Posteriorly
- Esophagus
- Descending thoracic aorta
- Thoracic vertebrae, approximately T5 to T8
- Azygos system and thoracic duct in the posterior mediastinum
Superiorly
- Great vessels: ascending aorta, pulmonary trunk, superior vena cava, and pulmonary veins
- Tracheal bifurcation is posterior to the great vessels
Inferiorly
- Diaphragm, especially its central tendon
- Left lobe of liver through the diaphragm
Laterally
- Mediastinal pleura and lungs
- Phrenic nerves and pericardiacophrenic vessels pass between the fibrous pericardium and mediastinal pleura.
Clinical relevance
- Enlargement of the left atrium may compress the esophagus, producing dysphagia.
- Pericardial fluid can accumulate around the heart and restrict filling, causing cardiac tamponade.
- The apex beat may shift laterally or downward in cardiomegaly or displacement of the mediastinum.
- Because the heart rests on the diaphragm, diaphragmatic movement affects its position.
The heart and pericardium occupy the middle mediastinum, while the posterior mediastinum behind them contains the esophagus and major vessels. Color Atlas of Human Anatomy, Vol. 2: Internal Organs, p. 70.
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