·
The pericardium (G. around the heart) is a double-walled fibroserous sac that
encloses the heart (G. kardia) and the roots of the great vessels.
·
It is located in the middle mediastinum,
posterior to the body of the sternum and the 2nd to 6th costal cartilages,
and anterior to T5 to T8 vertebrae.
- The
pericardium consists of two
parts: (1) a strong external layer composed of tough
fibrous tissue, called the fibrous pericardium,
and (2) an internal double-layered sac composed of a transparent membrane
called the serous pericardium.
- The
fibrous pericardium is the tough, more or less conical outer sac of
pericardium, which protects
the heart against sudden overfilling.
- Its
truncated apex is
pierced by the aorta, pulmonary trunk, and SVC.
- The
ascending aorta carries the pericardium superiorly beyond the heart to the level of the sternal
angle.
- The
external surface of the fibrous pericardium has a dull appearance and its
base rests on and is fused
with the central tendon of the diaphragm.
- Anteriorly,
the fibrous pericardium is attached to the posterior surface of the
sternum by condensations of connective tissue called sternopericardial ligaments.
- The
fibrous pericardium is also fused with the tunica adventitia of
the great vessels.
- Thus, the
fibrous pericardial sac is influenced by movements of the sternum,
diaphragm and heart.
- The
central tendon of the diaphragm and the pericardium are pierced by the IVC on
the right
side.
- The
fibrous pericardium extends 1 to 1.5 cm to the right of the sternum and 5
to 7.5 cm to the left of the median plane at the level of the 5th intercostal
space.
- It is
separated by the sternum and costal cartilages of the 2nd to
6th ribs by the lungs and pleura, except
where it is attached to the posterior surface of the sternum by thesternopericardial ligaments and
where the bulge of the heart intervenes.
- The serous
pericardium consists of two
layers: a parietal
pericardium and a visceral pericardium.
- The parietal pericardium is
fused to the internal surface of the fibrous pericardium and
is so closely adherent to it that they are difficult to separate.
- The visceral pericardium is
reflected onto the heart where it forms the epicardium, the
external layer of the heart wall.
- The
potential space between the parietal and visceral layers of the serous
pericardium is called the pericardial
cavity.
- It
normally contains a thin film of serous fluid that enables the heart to move and beat in a frictionless
environment.
- The visceral pericardium is reflected from the heart and great vessels to become continuous with the parietal pericardium. This is where the aorta and pulmonary trunk leave the heart and the superior and inferior venae cavae and pulmonary veins enter the heart.
