CorpusHuman Anatomy
CardiovascularMembrane

Pericardium

Pericardium

Also known as: pericardial sac

The pericardium is a fibroserous sac that encloses the heart and the roots of the great vessels. It has a tough outer fibrous layer and an inner double-layered serous membrane, with a thin film of lubricating fluid between the serous layers.

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Overview

Normal pericardial fluid≈15–50 mL
Sensory nerve (parietal)Phrenic nerve (C3–C5)
Volume causing acute tamponadeAs little as 100–200 mL

Fibrous pericardium. This is a cone of dense, inelastic connective tissue. Its base is fused with the central tendon of the diaphragm, and its apex blends with the adventitia of the great vessels. Sternopericardial ligaments anchor it to the back of the sternum. It holds the heart in place and prevents sudden over-distension. Because it cannot stretch acutely, even a small, rapidly forming effusion can compress the heart.

Serous pericardium. This has two layers. The parietal layer lines the inside of the fibrous pericardium. The visceral layer (epicardium) covers the heart. The two layers are continuous where they reflect around the great vessels. Between them is the pericardial cavity, which normally contains about 15–50 mL of serous fluid that lets the heart move without friction.

Sinuses. The reflections create two sinuses. The transverse pericardial sinus lies behind the ascending aorta and pulmonary trunk and in front of the SVC and atria. During cardiopulmonary bypass, surgeons pass a finger or ligature through it to isolate the great arteries. The oblique pericardial sinus is a blind recess behind the left atrium, bounded by the pulmonary veins and the IVC.

Location

Middle mediastinum. It encloses the heart and the proximal parts of the aorta, pulmonary trunk, SVC, IVC and pulmonary veins.

Parts & subdivisions

  1. Fibrous pericardium
    Tough outer collagenous sac, fused with the diaphragm and with the adventitia of the great vessels.
  2. Parietal serous pericardium
    Lines the fibrous pericardium. It is pain-sensitive through the phrenic nerves.
  3. Visceral serous pericardium (epicardium)
    Covers the heart surface and forms the outer layer of the heart wall.
  4. Pericardial cavity
    Potential space between the parietal and visceral layers, containing 15–50 mL of serous fluid.
  5. Transverse pericardial sinus
    Passage behind the arterial trunks (aorta, pulmonary trunk) and in front of the venous structures.
  6. Oblique pericardial sinus
    Inverted-U-shaped recess behind the left atrium.

Anatomy

Innervation

The fibrous and parietal serous layers are supplied by the phrenic nerves (C3–C5), which carry somatic pain. Pericardial pain can therefore be referred to the shoulder tip and supraclavicular region. The visceral layer receives only autonomic fibres and is insensitive to somatic pain.

Arterial supply

Fibrous and parietal layers: pericardiacophrenic arteries (from the internal thoracic arteries), with contributions from the musculophrenic arteries and from pericardial, bronchial, oesophageal and superior phrenic branches of the aorta. Visceral layer: the coronary arteries.

Venous drainage

Pericardiacophrenic veins to the brachiocephalic veins, and tributaries of the azygos system.

Relations

Laterally, the phrenic nerves and pericardiacophrenic vessels descend on the fibrous pericardium, between it and the mediastinal pleura. Anteriorly lie the sternum and thymic remnants. Posteriorly lie the oesophagus and descending aorta. Inferiorly lies the central tendon of the diaphragm.

Function

  • Anchors the heart within the mediastinum.
  • Limits acute over-distension of the heart.
  • Provides a lubricated, nearly frictionless space for the heart to move in.
  • Acts as a barrier to the spread of infection or tumour from neighbouring structures.

Clinical significance

Cardiac tamponade

When fluid or blood builds up rapidly in the pericardium, the inelastic fibrous layer cannot stretch, so the heart is compressed and cannot fill. As little as 100–200 mL can be enough.

Signs include Beck's triad (hypotension, raised JVP and muffled heart sounds) and pulsus paradoxus (an inspiratory fall in systolic pressure of more than 10 mmHg). The ECG may show electrical alternans.

Treatment is urgent pericardiocentesis, typically with a subxiphoid needle directed toward the left shoulder.

Acute pericarditis

Acute pericarditis is often viral, but it can also follow MI (including Dressler syndrome) or occur in uraemia and autoimmune disease. It causes sharp, pleuritic chest pain that is relieved by sitting forward, and a scratchy friction rub. The ECG shows widespread concave ("saddle-shaped") ST elevation with PR depression.

Constrictive pericarditis

In constrictive pericarditis, a thickened, fibrotic or calcified pericardium restricts diastolic filling. Signs include Kussmaul's sign (a JVP that rises on inspiration), a pericardial knock and right heart failure. Tuberculosis is an important cause worldwide.

Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.