Pericardium

ANATOMY • THORAX

Pericardium

Anatomy of the Pericardium — Study Notes

01

Definition

Definition

The pericardium (Greek: around heart) is a fibroserous sac that encloses the heart and roots of the great vessels.

It is situated in the middle mediastinum.

It Consists Of

1. Fibrous pericardium
2. Serous pericardium
02

Functions of Pericardium

  1. Protection of heart → shock absorption.
  2. Restricts excessive movements of the heart.
  3. Prevents overexpansion of the heart when blood volume increases.
  4. Prevents kinking of the great blood vessels.
  5. Minimizes friction between the heart and surrounding structures.
  6. Acts as a mechanical barrier for the spread of infection and other pathologies to the heart.
03

Subdivisions

The pericardium has two components:

1

Fibrous Pericardium

  • Outer layer of pericardium.
  • Forms a single-layered, thick, cone-shaped sac.
  • Encloses the heart.
  • Fuses with the roots of the major vessels.
2

Serous Pericardium

  • Inner double-layered blind sac of the pericardium.
  • Has two layers:

a. Parietal Layer

Lines the inner surface of the fibrous pericardium.

b. Visceral Layer / Epicardium

Lines the outer surface of the heart and great blood vessels.

04

Development

  1. When the head fold of the embryo is formed, the pericardial sac comes to lie in front of the developing heart tube.
  2. The heart tube undergoes folding and projects into the posterior wall of the sac.
  3. Arterial and venous ends of the heart tube are connected by a fold of pericardium called the dorsal mesocardium.
  4. Later, the dorsal mesocardium degenerates.
  5. A gap called the transverse sinus develops.
  6. Fibrous pericardium and parietal layer of serous pericardium develop from the somatopleuric layer of the pericardial sac.
  7. Visceral layer of serous pericardium develops from the splanchnopleuric layer of the pericardial sac.
05

Fibrous Pericardium

A conical sac made up of fibrous tissue.

The parietal layer of serous pericardium is attached to its deep surface.

Features

1. Apex

  • Blunt.
  • Lies at the level of the sternal angle.
  • Fused with:
Roots of the great vessels
Pretracheal fascia

2. Base

  • Broad.
  • Inseparably blended with the central tendon of the diaphragm.

3. Anteriorly

Connected to the upper and lower ends of the body of the sternum by:

Superior sternopericardial ligament
Inferior sternopericardial ligament

These ligaments are weak.

4. Posteriorly

Related to:

  • Principal bronchi
  • Oesophagus with the nerve plexus around it
  • Descending thoracic aorta

5. On Each Side

Related to:

  • Mediastinal pleura
  • Mediastinal surface of the lung
  • Phrenic nerve
  • Pericardiacophrenic vessels

6. Function

  • Protects the heart against sudden overfilling.
  • Prevents overexpansion of the heart.
06

Serous Pericardium

Thin, double-layered serous membrane lined by mesothelium.

a. Outer Layer / Parietal Pericardium

Fused with the fibrous pericardium.

b. Inner Layer / Visceral Pericardium / Epicardium

  • Fused to the heart.
  • Exception: along the cardiac grooves, where it is separated from the heart by blood vessels.

Continuity of the Two Layers

The two layers are continuous with each other at the roots of the great vessels:

Ascending aorta
Pulmonary trunk
Two venae cavae
Four pulmonary veins
07

Pericardial Cavity

A potential space between:

Parietal pericardium
Visceral pericardium
Normally contains a thin film of serous fluid: 15–20 ml

This Fluid

  • Lubricates the apposed surfaces.
  • Allows the heart to beat smoothly.
08

Contents of Pericardium

1
Heart with:
  • Cardiac veins
  • Coronary arteries
  • Nerves
2

Ascending aorta

3

Pulmonary trunk

4

Lower half of the superior vena cava

5

Terminal part of the inferior vena cava

6

Terminal parts of the pulmonary veins

09

Blood Supply

The fibrous and parietal pericardia are supplied by branches from:

1 Internal thoracic arteries
2 Musculophrenic arteries
3 Descending thoracic aorta
Venous Drainage

Veins drain into corresponding veins.

10

Nerve Supply

1. Fibrous and Parietal Pericardia

  • Supplied by the phrenic nerves.
  • Sensitive to pain.

2. Epicardium

  • Supplied by autonomic nerves of the heart.
  • Not sensitive to pain.
Note on Pain
  • Pain of pericarditis originates in the parietal pericardium alone.
  • Cardiac pain or angina originates in:
Cardiac muscle
Vessels of the heart
11

Sinuses of Pericardium

Sinuses of pericardium are the communicating zones developed by reflection of serous pericardium.

There Are Two Sinuses

1 Transverse sinus
2 Oblique sinus
12

Development of Pericardial Sinuses

The epicardium at the roots of the great vessels is arranged in the form of two tubes.

Arterial Tube

Encloses:

  • Ascending aorta
  • Pulmonary trunk

Present at the arterial end of the heart tube.

Venous Tube

Encloses:

  • Venae cavae
  • Pulmonary veins

Present at the venous end of the heart tube.

Transverse sinus

The passage between these two tubes is the transverse sinus of pericardium.

Formation of Oblique Sinus

  1. During development, initially the veins of the heart are crowded together.
  2. As the heart increases in size, these veins separate out.
  3. A pericardial reflection surrounds all of them.
  4. This forms the oblique pericardial sinus.
  5. This cul-de-sac is posterior to the left atrium.
13

Transverse Sinus

  • A horizontal gap between the arterial and venous ends of the heart tube.
  • Develops from degeneration of the central part of the dorsal mesocardium.

Boundaries

Anterior

Ascending aorta, pulmonary trunk

Posterior

Superior vena cava

Inferior

Left atrium

Superior

Bifurcation of pulmonary trunk

On Each Side

Opens into the main pericardial cavity.

14

Oblique Sinus

  • A narrow gap behind the heart.
  • Permits pulsations of the left atrium to take place freely.
  • Develops due to rearrangement of veins at the venous end.

Boundaries

Anterior

Left atrium

Posterior

Parietal pericardium

On the Right

Two right pulmonary veins and inferior vena cava

On the Left

Superior

Inferior

Two Left Pulmonary Veins

Two left pulmonary veins

Reflection

Reflection of visceral pericardium along the right and left superior pulmonary veins (along the upper margin of left atrium).

Communication

Communicates with the main pericardial cavity.

15

Clinical Anatomy

01

Significance of Transverse Pericardial Sinus

During heart surgery, the ligature is passed through the transverse sinus around:

Aorta
Pulmonary trunk
02

Pericarditis

  • Pericarditis = inflammation of the pericardium.
  • Fibrous and parietal pericardia are pain sensitive.
  • Therefore, pericarditis induces pain.
03

Pericardial Friction Rub

  • In pericarditis, smooth opposing surfaces of serous pericardium become rough.
  • This results in pericardial friction rub.
  • It can be heard as the rustle of silk using a stethoscope.
04

Pericardial Effusion

  • Collection of fluid in the pericardial cavity is called pericardial effusion.
  • The fluid:
Compresses the heart.
Restricts venous filling during diastole.
Reduces cardiac output.
  • Radiologically, it shows water-bottle heart on chest radiograph.
  • It produces an enlarged cardiac shadow in the shape of a flask or water bottle.
05

Pericardiocentesis

Pericardial effusion can be drained by puncturing:

  1. Left 5th or 6th intercostal space, just lateral to the sternum, or
  2. The angle between the xiphoid process and left costal margin.

The needle is directed:

1. Upwards
2. Backwards
3. To the left.
06

Cardiac Tamponade

  • A type of pericardial effusion that results in compression of the heart.
  • Occurs due to the inelastic nature of tough fibrous pericardium.
  • Reduces filling of cardiac chambers during diastole.
  • Thus, it reduces cardiac output.
07

Mitral Stenosis

  • In mitral stenosis, the left atrium enlarges.
  • It compresses the oesophagus.
  • This causes dysphagia.
Pericardium — Anatomy Study Notes Anatomy → Thorax → Pericardium