Figure 27.2 Surface Features Of The Heart

Navigating the heart's intricate surface features is essential for understanding its function and potential pathologies. The heart, the powerhouse of the circulatory system, exhibits a complex external anatomy critical to its role in pumping blood throughout the body.

Unveiling the Surface: An Introduction to Cardiac Landmarks

The heart, roughly the size of a clenched fist, is nestled within the mediastinum, the space between the lungs. Its cone-like shape features a broad base superiorly and a pointed apex inferiorly. Understanding the surface features requires familiarity with the major vessels entering and exiting the heart, as well as the grooves and chambers that define its structure.

Major Players: Vessels and Chambers

Aorta: The largest artery in the body, carrying oxygenated blood from the left ventricle to the systemic circulation.
Pulmonary Artery: Transports deoxygenated blood from the right ventricle to the lungs for oxygenation.
Superior and Inferior Vena Cava: Large veins that return deoxygenated blood from the body to the right atrium.
Pulmonary Veins: Carry oxygenated blood from the lungs to the left atrium.
Right Atrium: Receives deoxygenated blood from the superior and inferior vena cava and the coronary sinus.
Right Ventricle: Pumps deoxygenated blood into the pulmonary artery.
Left Atrium: Receives oxygenated blood from the pulmonary veins.
Left Ventricle: Pumps oxygenated blood into the aorta.

Grooves and Boundaries: Defining the Landscape

Coronary Sulcus (Atrioventricular Groove): Encircles the heart, separating the atria from the ventricles. It houses the coronary arteries and the coronary sinus.
Anterior Interventricular Sulcus: Located on the anterior surface of the heart, marking the boundary between the right and left ventricles. The left anterior descending (LAD) artery runs within this sulcus.
Posterior Interventricular Sulcus: Found on the posterior surface, delineating the separation between the right and left ventricles. The posterior interventricular artery runs here.

A Closer Look: Anterior Surface Features

The anterior view of the heart reveals several crucial structures. The most prominent is the anterior interventricular sulcus, a groove running obliquely from the coronary sulcus towards the apex. This sulcus houses the left anterior descending artery (LAD), a major coronary artery supplying blood to the anterior wall of the left ventricle and the anterior two-thirds of the interventricular septum. Blockage of the LAD, often referred to as the "widow maker," can lead to extensive myocardial infarction.

Key Anterior Structures:

Right Ventricle: Dominates the anterior surface.
Left Ventricle: Appears on the left side of the anterior surface.
Right Atrium: Located superiorly and to the right, receiving blood from the superior and inferior vena cava. Part of the right atrium, the right auricle, is visible, an ear-like appendage that increases the atrial volume.
Left Atrium: Mostly hidden posteriorly, but a portion, the left auricle, is visible on the superior-left aspect of the anterior surface.
Ascending Aorta: Emerges from the left ventricle, arching posteriorly to form the aortic arch.
Pulmonary Trunk: Arises from the right ventricle, bifurcating into the right and left pulmonary arteries.
Coronary Sulcus: Separates the atria from the ventricles, visible across the anterior surface.

Posterior Surface: A Different Perspective

The posterior view provides a different perspective, highlighting the relationship between the heart and the great vessels. The posterior interventricular sulcus, containing the posterior interventricular artery, is a prominent feature. This artery typically arises from the right coronary artery, though variations exist.

Key Posterior Structures:

Left Atrium: The dominant feature of the posterior surface, receiving blood from the four pulmonary veins.
Right Atrium: Visible on the right side, with the openings of the superior and inferior vena cava clearly visible.
Left Ventricle: Forms a significant portion of the posterior surface.
Right Ventricle: Less prominent on the posterior surface compared to the anterior view.
Coronary Sinus: A large vein located in the coronary sulcus on the posterior side, collecting blood from the heart muscle itself and draining into the right atrium.
Pulmonary Veins: Four veins (two from each lung) entering the left atrium.
Superior and Inferior Vena Cava: Entering the right atrium from above and below, respectively.

Right Lateral View: Unveiling the Right Side

The right lateral view emphasizes the right atrium and ventricle. The superior and inferior vena cava are clearly visible entering the right atrium. The crista terminalis, a C-shaped ridge inside the right atrium, is important as the origin of the pectinate muscles. The fossa ovalis, a remnant of the fetal foramen ovale, is also visible in the interatrial septum.

Key Right Lateral Structures:

Right Atrium: Dominates the view.
Right Ventricle: Clearly visible.
Superior Vena Cava: Entering the right atrium.
Inferior Vena Cava: Entering the right atrium.
Coronary Sulcus: Separating the atrium and ventricle.
Pulmonary Trunk: Arising from the right ventricle.

Left Lateral View: A Glimpse of the Left

The left lateral view highlights the left ventricle and atrium. The left auricle is a prominent feature. The aorta arching superiorly from the left ventricle is also visible.

Key Left Lateral Structures:

Left Ventricle: Dominates the view.
Left Atrium: Visible posteriorly.
Aorta: Arising from the left ventricle.
Left Auricle: A prominent feature.
Pulmonary Veins: Entering the left atrium (though partially obscured).

Detailed Anatomy: Sulci, Auricles, and Coronary Vessels

Beyond the basic chambers and vessels, a deeper understanding of the surface features requires examining the specific sulci (grooves), auricles (appendages), and the coronary vasculature.

Sulci: Lines of Demarcation

The sulci are not simply superficial grooves; they represent important anatomical landmarks and contain vital blood vessels.

Coronary Sulcus: As mentioned, this encircles the heart, separating the atria from the ventricles. It is also home to the right coronary artery, the circumflex artery (a branch of the left coronary artery), and the coronary sinus.
Anterior and Posterior Interventricular Sulci: These mark the division between the right and left ventricles. The left anterior descending (LAD) artery resides in the anterior sulcus, while the posterior interventricular artery (PDA) occupies the posterior sulcus. Variations in coronary artery dominance exist, with the PDA arising from the right coronary artery in most individuals, but from the circumflex artery in others.

Auricles: Atrial Appendages

The auricles are small, ear-like extensions of the atria. They increase the capacity of the atria and play a role in atrial contraction.

Right Auricle: Located on the anterior surface of the right atrium.
Left Auricle: Located on the superior-left aspect of the anterior surface, extending from the left atrium. The left auricle is particularly important because it is a common site for thrombus (blood clot) formation in patients with atrial fibrillation.

Coronary Vasculature: The Heart's Lifeline

The coronary arteries are responsible for supplying the heart muscle (myocardium) with oxygenated blood. Their location and distribution are crucial to understanding the consequences of coronary artery disease.

Right Coronary Artery (RCA): Arises from the right aortic sinus and travels along the coronary sulcus. It typically supplies the right atrium, right ventricle, and the posterior portion of the left ventricle. It also gives rise to the posterior interventricular artery (PDA) in most individuals.
Left Coronary Artery (LCA): Arises from the left aortic sinus and quickly bifurcates into the left anterior descending (LAD) artery and the circumflex artery.
Left Anterior Descending (LAD) Artery: Travels down the anterior interventricular sulcus, supplying the anterior wall of the left ventricle and the anterior two-thirds of the interventricular septum.
Circumflex Artery: Curves around the left side of the heart in the coronary sulcus, supplying the left atrium and the posterior and lateral walls of the left ventricle.

Understanding the surface location of these arteries is critical during surgical procedures, such as coronary artery bypass grafting (CABG).

Clinical Significance: Linking Anatomy to Pathology

Knowledge of the heart's surface features is not merely academic; it has direct clinical relevance.

Myocardial Infarction (Heart Attack): Blockage of a coronary artery leads to ischemia (lack of blood supply) and subsequent infarction (tissue death) of the myocardium. The location of the infarct depends on which artery is blocked. For example, LAD occlusion typically results in anterior wall myocardial infarction, while RCA occlusion can lead to inferior or posterior wall infarction.
Coronary Artery Bypass Grafting (CABG): This surgical procedure involves grafting a healthy blood vessel (typically from the leg or chest) to bypass a blocked coronary artery. Surgeons must have a precise understanding of the coronary arteries' surface location to perform the bypass effectively.
Atrial Fibrillation: This common arrhythmia is often associated with thrombus formation in the left auricle, increasing the risk of stroke.
Pericarditis: Inflammation of the pericardium (the sac surrounding the heart) can cause chest pain and may lead to pericardial effusion (fluid accumulation around the heart). Understanding the heart's surface anatomy helps in pericardiocentesis, a procedure to drain excess fluid from the pericardial sac.
Cardiac Tamponade: This life-threatening condition occurs when fluid accumulation in the pericardial sac compresses the heart, impairing its ability to pump blood. Knowledge of the heart's location and surrounding structures is crucial for emergency pericardiocentesis.

Exploring Deeper: Beyond the Surface

While this discussion focuses on the surface features, it's important to remember that the external anatomy is intimately linked to the internal structure of the heart. The chambers, valves, and conduction system all work together to ensure efficient blood flow. Understanding the relationship between the surface features and the internal components is essential for a comprehensive understanding of cardiac physiology and pathology.

Variations and Anomalies: The Uniqueness of Every Heart

It's crucial to acknowledge that the heart's anatomy can vary between individuals. Coronary artery dominance (whether the PDA arises from the RCA or the circumflex artery) is a common variation. Other anomalies, such as congenital heart defects, can significantly alter the heart's surface appearance. Recognizing these variations is vital for accurate diagnosis and treatment.

Techniques for Visualizing the Heart

Several imaging techniques allow clinicians to visualize the heart and its surface features:

Echocardiography: Uses ultrasound to create images of the heart.
Computed Tomography (CT) Angiography: Provides detailed images of the coronary arteries.
Magnetic Resonance Imaging (MRI): Offers high-resolution images of the heart and surrounding structures.
Cardiac Catheterization and Angiography: Involves inserting a catheter into a blood vessel and injecting contrast dye to visualize the coronary arteries.

These techniques allow for detailed assessment of the heart's surface features, aiding in the diagnosis and management of various cardiac conditions.

Learning Resources: Building Your Knowledge

Numerous resources are available to further explore the heart's anatomy:

Anatomical Atlases: Provide detailed illustrations of the heart's surface features.
Textbooks: Offer comprehensive coverage of cardiac anatomy and physiology.
Online Resources: Websites and interactive tutorials provide virtual dissections and 3D models of the heart.
Clinical Rotations: Observing cardiac procedures firsthand provides valuable practical experience.

By utilizing these resources, students and healthcare professionals can develop a strong foundation in cardiac anatomy.

Conclusion: The Heart Unveiled

Understanding the surface features of the heart is fundamental to comprehending its function and pathology. From the major vessels and chambers to the intricate sulci and coronary arteries, each structure plays a vital role in the heart's ability to pump blood throughout the body. By mastering this anatomical knowledge, healthcare professionals can effectively diagnose and treat a wide range of cardiac conditions, ultimately improving patient outcomes. This exploration serves as a stepping stone to appreciating the heart's complex and beautiful design, a testament to the marvel of human biology.