The Pericardium: Anatomy and Function of the Heart's Protective Sac

The pericardium is a double-walled fibroserous sac enclosing the heart and proximal great vessels.

Layers

• Fibrous pericardium: Tough outer connective tissue layer anchoring the heart in the mediastinum.
• Serous pericardium: Inner layer with parietal (lining fibrous layer) and visceral (epicardium, adherent to myocardium) portions.

Pericardial Cavity

The potential space between parietal and visceral layers contains 15–50 mL of serous fluid. This lubricant minimizes friction during cardiac contractions.

Functions

• Mechanical protection and fixation.
• Lubrication for frictionless beating.
• Barrier against infection spread from adjacent structures.
• Prevention of acute cardiac overdistension.

Pathologies include pericarditis (inflammation), effusion (fluid accumulation), and tamponade (hemodynamic compromise from compressive effusion).