Anatomy of the heart the pericardium

The pericardium is a double-walled sac containing the heart and the roots of the great vessels.

• The pericardium is a sac that embeds the heart. It is pierced by the great vessels. Morphologically, it is a conical-shaped, double-walled fibro-serous membrane.
• The pericardial sac rests posteriorly to the sternum at the level of second to sixth costal cartilages and T5-T8 vertebrae.
• The pericardium is made of two layers:
  • Fibrous pericardium
    • Hard protective external layer
    • Attached to sternum anteriorly by sterno-pericardial ligaments and fused with the central tendon of the diaphragm and great vessels to allow mobility of the pericardial sac against sudden cardiac overfilling.
  • Serous Pericardium
    • Smooth internal layer made of 2 components:
      • Parietal: reflects onto fibrous pericardium
      • Visceral: reflects onto heart and great vessels and forms the epicardium, the external layer of the heart wall.
• Pericardial cavity: Potential space between parietal and visceral layers. It contains a serous fluid film that occupies the cavity and functions as lubricant against friction by all chest movements.

• Pericardial sinuses are channels or chambers between the visceral and parietal pericardia.
• Transverse sinus:
  • Located posterior to the pulmonary trunk and ascending aorta at the level between the superior vena cava and aortic arch.
  • Formed after dorsal mesocardium rupture embryonically
  • Functional role is to allow the unhindered expansion of great arteries posteriorly during cardiac systole.
  • Utilized surgically to pass surgical clamps or place ligatures around great arteries.
• Oblique sinus:
  • A blind recess (cul-de-sac) posterior to the left atrium between superior vena cava, right and left pulmonary veins inferior to the transverse sinus.
  • Formed embryonically by the incorporation of the pulmonary vein tributaries into the left atrium.
  • Functional role believed to be the expansion of the left atrium upon normal collapse of the thorax.^[1][2][3]

Below are images showing the pericardium and pericardial sinuses.

• 
  The pericardium
• 
  The pericardial sinuses

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