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M01.05.017 The Surfaces and Borders of the Heart
The heart is a hollow, muscular pump located in the middle mediastinum, and its structure is complex with multiple surfaces, borders, and sulci. Understanding the orientation and features of the heart is essential for medical students, especially when considering its clinical relevance in procedures such as coronary artery bypass grafting.
Orientation and Surfaces of the Heart
The heart can be described as a “pyramid which has fallen over,” with the apex pointing in an anteroinferior direction. This orientation affects the location of the heart’s surfaces, each formed by different chambers. The five main surfaces of the heart are:
Surfaces of the Heart
| Surface | Formation |
|---|---|
| Anterior (Sternocostal) | Right ventricle |
| Posterior (Base of Pyramid) | Left atrium |
| Inferior (Diaphragmatic) | Left and right ventricles |
| Right Pulmonary | Right atrium |
| Left Pulmonary | Left ventricle |
Points to Remember:
- The heart’s shape is like a pyramid with its apex pointing anteroinferiorly.
- The different surfaces are formed by the various chambers of the heart.
Borders of the Heart
The borders of the heart separate its surfaces and help define its shape. There are four primary borders of the heart:
Borders of the Heart
| Border | Formation |
|---|---|
| Right Border | Right atrium |
| Inferior Border | Left and right ventricles |
| Left Border | Left ventricle (and part of left atrium) |
| Superior Border | Right and left atria and the great vessels |
Points to Remember:
- The right border is formed by the right atrium.
- The inferior border is formed by the left and right ventricles.
- The left border is mostly formed by the left ventricle.
- The superior border is formed by the atria and great vessels.
Sulci of the Heart
The external surface of the heart contains grooves or sulci, which correspond to the internal divisions of the heart’s chambers. These sulci are important landmarks for identifying coronary arteries and veins.
Key Sulci of the Heart
| Sulcus | Location | Structures Present |
|---|---|---|
| Coronary Sulcus (Atrioventricular Groove) | Encircles the heart, separating atria from ventricles | Right coronary artery, circumflex branch, small cardiac vein, coronary sinus |
| Anterior Interventricular Sulcus | On the anterior surface, between ventricles | Anterior interventricular artery (left anterior descending artery), great cardiac vein |
| Posterior Interventricular Sulcus | On the posterior surface, between ventricles | Posterior interventricular artery, middle cardiac vein |
Points to Remember:
- The coronary sulcus separates the atria from the ventricles and contains key arteries and veins.
- The interventricular sulci (anterior and posterior) separate the ventricles and contain major arteries.
Pericardial Sinuses
The pericardial sinuses are passageways formed by the folding of the pericardium around the great vessels. These sinuses are important in clinical procedures such as coronary artery bypass grafting.
Types of Pericardial Sinuses
| Sinus | Location | Clinical Relevance |
|---|---|---|
| Oblique Pericardial Sinus | Located posteriorly to the heart | A blind-ending passageway on the posterior surface of the heart |
| Transverse Pericardial Sinus | Found superior to the heart | Used in coronary artery bypass grafting to ligate arteries |
Points to Remember:
- The oblique pericardial sinus is a blind-ending passageway.
- The transverse pericardial sinus is clinically significant in procedures like coronary artery bypass grafting.
Clinical Relevance: Transverse Pericardial Sinus
The transverse pericardial sinus plays a key role in coronary artery bypass grafting. Its location allows for identification and ligation of the arterial vessels, separating the arterial and venous vessels of the heart.
Location of the Transverse Pericardial Sinus
- Posterior to the ascending aorta and pulmonary trunk
- Anterior to the superior vena cava
- Superior to the left atrium
In coronary artery bypass grafting, this sinus is used to access the arteries and perform necessary interventions.
Points to Remember:
- The transverse pericardial sinus separates the arterial and venous vessels of the heart.
- It is clinically significant in procedures like coronary artery bypass grafting.