Human Anatomy Vol 1

THORAX

Visceral layer of

serous pericardium

fused with myocardium

Primordium

of heart

Pericardlal cavity

Parietal layer of

serous pericardium

fused with fibrous

pericardium

Fig. 18.2: Development of the layers of serous pericardium

Arch of aorta

Pulmonary

artery

Pulmonary

vetns

Sternopericard ial

ligaments

lnferior
vena cava
Fig. 18.3: The relations of the fibrous pericardium to the roots
of the great vessels, to the diaphragm and sternum

Fibrous

pericardium

Parietal layer of

serous pericardium

Visceral layer or

epicardium

6 It protects the heart against sudden overfilling and

prevents over expansion of the heart.

SEROUS PERICARDIUM

Serous pericardium is thin, double-layered serous

membrane lined by mesothelium. The outer layer or

parietal pericardium is fused with the fibrous peri-

cardium. The inner layer or the visceral pericardium,

or epicardium is fused to the heart, except along the

cardiac grooves, where it is separated from the heart

by blood vessels. The two layers are continuous with

each other at the roots of the great vessels, i.e. ascending

aorta,pulmonary trunk, two venae cavae, and four pul-

monary veins.

Thepericardial caaity is a potential space between the

parietal pericardium and the visceral pericardium. It

contains only a thin film of serous fluid which lubricates

the apposed surfaces and allows the heart to beat

smoothly.

Sinuses of Pericordium

The epicardium at the roots of the great vessels is

arranged in form of two tubes. The arterial tube

encloses the ascending aorta and the Pulmonary trunk

at the arterial end of the heart tube, and the venous

tube encloses the venaeicavae and pulmonary veins at

the venous end of the heart tube. The passage between

the two tubes is known as the transaerse sinus of

pericardium. During development, to begin with, the

veins of the heart are crowded together. As the heart

increases in size and these veins separate out, a

pericardial reflection surrounds all of them and forms

the oblique pericardial sinus. This cul-de-sac is posterior

to the left atrium (Fig.18.a).

The transuerse sinus is a horizontal gap between the

arterial and venous ends of the heart tube. It is bounded

Pericardial cavity

Heart muscle

Diaphragm

(a) (b)

Figs 18.1a and b: (a) Lines of incision, and (b) layers of the pericardium

Diaphragm