The pericardium, also called pericardial sac, is a double-walled sac containing the
heart
The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
and the roots of the
great vessels. It has two layers, an outer layer made of strong
connective tissue (fibrous pericardium), and an inner layer made of
serous membrane (serous pericardium).
It encloses the pericardial cavity, which contains
pericardial fluid,
and defines the
middle mediastinum. It separates the heart from interference of other structures, protects it against
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
and
blunt trauma, and
lubricate
Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.
Lubrication mechanisms such as fluid-lubrica ...
s the heart's movements.
The English name originates from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
prefix "''peri-''" (περί; "around") and the suffix "''-cardion''" (κάρδιον; "heart").
Anatomy
The pericardium is a tough fibroelastic sac which covers the heart from all sides except at the cardiac root (where the
great vessels join the heart) and the bottom (where only the serous pericardium exists to cover the upper surface of the
central tendon of
diaphragm
Diaphragm may refer to:
Anatomy
* Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
* Pelvic diaphragm or pelvic floor, a pelvic structure
* Urogenital diaphragm or triangular ligament, a pelvic structure
Other
* Diap ...
). The fibrous pericardium is semi-rigid, while the serous pericardium is quite pliable.
The same mesothelium that constitutes the serous pericardium also covers the heart as the
epicardium, resulting in a continuous
serous membrane invaginated onto itself as two opposing surfaces (over the fibrous pericardium and over the heart). This creates a pouch-like
potential space around the heart enclosed between the two opposing serosal surfaces, known as the pericardial space or pericardial cavity, which is filled with a small amount of
serous fluid to lubricate the heart's movements and cushions it from any external jerk or shock.
Fibrous
The fibrous pericardium is the outside layer of the pericardium, made up of
dense and
loose connective tissue. While capable of some
change in shape, it is largely non-pliable, which acts to protect the heart against blunt forces and sudden pressure change from the outside. It is continuous with the
outer adventitial layer of the neighboring
great blood vessels, fused with the central fibrous area of the diaphragm on its posterior aspect and attached to the posterior surface of the
sternum by the sternopericardial ligaments.
Serous
The serous pericardium, in turn, is divided into two parts:
*The ''parietal serous pericardium'', which lines the interior side of the superficial portion of the pericardial sac, is fused to and inseparable from the fibrous pericardium
*The ''visceral serous pericardium'', also known as the epicardium, covers the
myocardium of the heart
[ and can be considered its serosa. It is largely made of a mesothelium overlying some elastin-rich loose connective tissue. During ventricular contraction, the wave of depolarization moves from the endocardial to the epicardial surface.
Both of these layers function in lubricating the heart to prevent friction during heart activity.
The visceral serous pericardium extends to the root of the great vessels and joins the parietal serous pericardium at the anatomical base of the heart. This junction occurs at two areas: the ventricular outflow tracts where the aorta and pulmonary trunk leave the heart, and the inflow tracts where the ]superior
Superior may refer to:
*Superior (hierarchy), something which is higher in a hierarchical structure of any kind
Places
*Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state
*Lake ...
/ inferior vena cava and pulmonary veins enter the heart. The root of the great vessels and the associated reflections of the serous pericardium creates various smaller sacs and tunnels known as '' pericardial sinuses'', as well as radiographically significant ''pericardial recesses'', where pericardial fluid can pool and mimic mediastinal lymphadenopathy.[
]
Anatomical relationships
* Surrounds heart and bases of pulmonary artery and aorta.
* Deep to sternum and anterior chest wall.
* The right phrenic nerve
The phrenic nerve is a mixed motor/sensory nerve which originates from the C3-C5 spinal nerves in the neck. The nerve is important for breathing because it provides exclusive motor control of the diaphragm, the primary muscle of respiration. In ...
passes to the right of the pericardium.
* The left phrenic nerve passes over the pericardium of the left ventricle.
* Pericardial arteries supply blood to the dorsal portion of the pericardium.
Function
The pericardium sets the heart in mediastinum and limits its motion, protects it from infection, lubricates it and prevents excessive dilation in cases of acute volume overload.
Clinical significance
Inflammation of the pericardium is called pericarditis. This condition typically causes chest pain that spreads to the back and is made worse by lying flat. In patients suffering with pericarditis, a pericardial friction rub
A pericardial friction rub, also pericardial rub, is an audible medical sign used in the diagnosis of pericarditis. Upon auscultation, this sign is an extra heart sound of to-and-fro character, typically with three components, two systolic and ...
can often be heard when listening to the heart with a stethoscope. Pericarditis is often caused by a viral infection ( glandular fever, cytomegalovirus, or coxsackievirus), or more rarely with a bacterial infection, but may also occur following a myocardial infarction
A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which ma ...
. Pericarditis is usually a short-lived condition that can be successfully treated with painkillers, anti-inflammatories
Anti-inflammatory is the property of a substance or treatment that reduces inflammation or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs remedy pain by reducing inflammation as op ...
, and colchicine. In some cases, pericarditis can become a long-term condition causing scarring of the pericardium which restricts the heart's movement, known as constrictive pericarditis
Constrictive pericarditis is a medical condition characterized by a thickened, fibrotic pericardium, limiting the heart's ability to function normally. In many cases, the condition continues to be difficult to diagnose and therefore benefits from ...
. Constrictive pericarditis is sometimes treated by surgically removing the pericardium in a procedure called a pericardiectomy.
Fluid can build up within the pericardial space, referred to as a pericardial effusion
A pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. The pericardium is a two-part membrane surrounding the heart: the outer fibrous connective membrane and an inner two-layered serous membrane. The two layers of t ...
. Pericardial effusions often occur secondary to pericarditis, kidney failure
Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney failure is classified as eit ...
, or tumour
A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s and frequently do not cause any symptoms. Large effusions or effusions that accumulate rapidly can compress the heart and restrict diastolic ventricular filling in a condition known as cardiac tamponade, causing pulsus paradoxus
Pulsus paradoxus, also paradoxic pulse or paradoxical pulse, is an abnormally large decrease in stroke volume, systolic blood pressure and pulse wave amplitude during inspiration. The normal fall in pressure is less than 10 mmHg. When the drop i ...
and potentially fatal circulatory failure. Fluid can be removed from the pericardial space for diagnosis or to relieve tamponade using a syringe in a procedure called pericardiocentesis. For cases of recurrent pericardial effusion, an operation to create a hole between the pericardial and pleural spaces can be performed, known as a pericardial window or ''pericardiostomy''.
The congenital absence of pericardium is rare. When it happens, it is usually occurs on the left side. Those affected usually do not have any symptoms and they are usually discovered incidentally. About 30 to 50 percent of the affected people have other heart abnormalities such as atrial septal defect, patent ductus arteriosus, bicuspid aortic valve, and lung abnormalities. On chest X–ray, the heart looks posteriorly rotated. Another feature is the sharp delineation of pulmonary artery and transverse aorta due to lung deposition between these two structures. If there is partial absence of pericardium, there will be bulge of the left atrial appendage. On CT and MRI scans, similar findings as chest X–ray can be shown. The left sided partial pericardium defect is difficult to see because even a normal pericardium is difficult to be seen on CT and MRI. A complete pericardial defect will show the heart displaced to the left with part of the lungs squeezed between inferior border of heart and diaphragm.
Additional images
File:Slide15gggg.JPG, Fibrous pericardium
Image:Cytology of normal mesothelium.jpg, Cytology of the normal mesothelial cells that line the pericardium, with typical features.[Image by Mikael Häggström, MD. Sources for mentioned features:]
-
- Wright's stain.
References
External links
* – "Mediastinum: Pericardium (pericardial sac)"
* ()
* – "MRI of chest, lateral view"
{{Authority control
Cardiac anatomy