The heart is a crucial muscle that functions as a pump, ensuring blood circulation throughout the body. Understanding its anatomy, protective layers, and blood supply is crucial for medical professionals and students.
Heart Anatomy
The heart consists of four chambers:
- Right Atrium (RA) – Receives deoxygenated blood from the superior vena cava (SVC), inferior vena cava (IVC), and the coronary sinus.
- Right Ventricle (RV) – Pumps blood into the pulmonary arteries for oxygenation. It is the most anterior part of the heart and is prone to trauma.
- Left Atrium (LA) – The most posterior chamber, located near the esophagus. LA enlargement, as seen in mitral stenosis, can compress the esophagus (causing dysphagia) or the left recurrent laryngeal nerve (leading to hoarseness – Ortner syndrome).
- Left Ventricle (LV) – The strongest chamber, responsible for systemic circulation. It makes up about 2/3 of the inferior (diaphragmatic) cardiac surface, while the RV contributes about 1/3.
Key Anatomical Landmarks
- Aortic Knob – Visible in imaging, marking the aortic arch.
- Azygos Vein – Drains blood from the thoracic wall into the SVC.
- The descending aorta transports oxygen-rich blood to the lower regions of the body.
Pericardium: The Protective Layers of the Heart
The heart is enclosed within a three-layered pericardium, which protects and anchors it:
- Fibrous Pericardium – The tough outer layer that prevents overexpansion.
- Parietal Pericardium – The middle layer, lining the fibrous pericardium.
- Epicardium (Visceral Pericardium) – The inner layer, closely attached to the heart.
Between the parietal pericardium and epicardium, there is a pericardial space containing fluid that reduces friction.
Clinical Correlation: Pericarditis
- Inflammation of the pericardium can cause sharp chest pain that worsens with inspiration.
- Pain may radiate to the neck, arms, or shoulders (often left-sided) due to phrenic nerve innervation.
Coronary Blood Supply: Nourishing the Heart
The heart receives its blood supply from the coronary arteries, which branch from the aorta.
Left Coronary Artery (LCA)
- Left Anterior Descending (LAD) Artery:
- Supplies the anterior 2/3 of the interventricular septum and the anterolateral papillary muscle.
- It is the most commonly occluded artery, leading to heart attacks.
- Left Circumflex (LCX) Artery:
- Contributes to the lateral and posterior regions of the left ventricle.
Right Coronary Artery (RCA)
- Supplies the SA node and AV node, essential for heart rhythm.
- Acute Marginal Artery – Supplies the right ventricle.
- Posterior Descending Artery (PDA) –
- Nourishes the posterior 1/3 of the interventricular septum and the posterior 2/3 of the ventricular walls.
Types of Coronary Circulation
- Right-dominant (Most common) – PDA originates from the RCA.
- Left-dominant – PDA arises from the LCX.
- Codominant – PDA arises from both RCA and LCX.
Coronary Blood Flow Timing
Unlike most arteries, coronary blood flow peaks during early diastole (heart relaxation), ensuring adequate perfusion to the left ventricle and interventricular septum.
Venous Drainage
The coronary sinus, located in the left atrioventricular (AV) groove, collects deoxygenated blood and drains it into the right atrium.
Conclusion
Understanding heart anatomy, its protective layers, and blood supply is essential for diagnosing and managing cardiovascular diseases. Whether studying for medical exams or enhancing clinical knowledge, grasping these fundamentals aids in better patient care.