Pericardium

# Overview
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. Morphologically, it is a conical-shaped, double-walled fibro-serous membrane. It rests posteriorly to the sternum at the level of second to sixth costal cartilages and T5-T8 vertebrae.

# Layers
- The pericardium is made up 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 up 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
- 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
- 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 up 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
- Smooth internal layer made up 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
- 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
- There are two small chambers or sinuses located where the visceral and parietal pericardia are continuous with one another within the pericardial cavity.
- 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.
- 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
- 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

# Diseases of the Pericardium
- Pericarditis is an inflammatory condition of the pericardium.
- Pericardial effusion is fluid accumulation in the pericardial sac.
- Constrictive pericarditis occurs when there is a scar encasing, the heart that chronically constricts the filling of the heart.
- Cardiac tamponade is a medical emergency in which fluid in the pericardial sac acutely restricts the filling of the heart. This requires surgical drainage or pericardiocentesis.

# Additional Images
- The phrenic nerve and its relations with the vagus nerve.
- Thoracic portion of the sympathetic trunk.
- Liver with the septum transversum. Human embryo 3 mm long.
- The thymus of a full-time fetus, exposed in situ.