The Pericardium
The pericardium is a fibroserous sac that encloses the heart and the roots of the great vessels. It consists of two main layers: the fibrous pericardium and the serous pericardium.
Layers of the Pericardium
- Fibrous Pericardium: The tough, outer, inelastic layer. It protects the heart, anchors it to the diaphragm, and prevents overfilling.
- Serous Pericardium:
- Parietal Layer: Lines the inner surface of the fibrous pericardium.
- Visceral Layer (Epicardium): Adheres directly to the heart muscle.
- Pericardial Cavity: The potential space between the parietal and visceral layers, containing a small amount of serous fluid to reduce friction during heartbeat.
Clinical Significance
| Condition | Key Feature |
|---|---|
| Pericarditis | Inflammation causing chest pain (relieved by leaning forward) and a friction rub. |
| Cardiac Tamponade | Compression of the heart due to fluid accumulation in the pericardial cavity. Characterized by Beck’s Triad: hypotension, jugular venous distension (JVD), and distant heart sounds. |
High-Yield Exam Pearl:
The fibrous pericardium is innervated by the phrenic nerves (C3–C5), which also provide sensory fibers to the central diaphragm. This explains why pericardial pain is frequently referred to the shoulder or supraclavicular region.