553 



tissue; in man much of its diaphragmatic attachment consists of loose fibrous tissue which can 

 be readily broken down, but over a small area the central tendon of the Diaphragm and the 

 pericardium are completely fused. Above, the fibrous pericardium not only blends with the 

 external coats of the great vessels, but is continuous with the pretracheal layer of the deep cervical 

 fascia. By means of these upper and lower connections it is securely anchored within the 

 thoracic cavity. It is also attached to the posterior surface of the sternum by two fibrous bands, 

 the superior and inferior sternopericardial ligaments (ligg. sternopericardiaca) ; the upper pass- 

 ing to the manubrium, and the lower to the ensiform cartilage. On each side of the ascending 

 aorta the pericardium sends upward a diverticulum; the one on the left side, somewhat conical 

 in shape, passes upward and outward, between the arch of the aorta and the pulmonary artery, 

 as far as the ductus arteriosus, where it terminates in a blind extremity, which is attached by 

 loose connective tissue to this impervious duct (Fig. 411). The one on the right side passes 

 upward and to the right, between the ascending aorta and superior vena cava (precava), and 

 also terminates in a blind extremity. 



Eight phrenic 

 nerve 



Line of reflection of 

 serous pericardium 



Transverse sinus 

 of pericardium 



Openings of 

 right pulmo- 

 nary reins 



Openings of left 

 pulmonary veins 



Left phrenis 

 nerve 



Pericardium 



FIG. 413. Posterior wall of the pericardial sac, showing the lines of reflection of the serous pericardium on 



the great vessels. 



The vessels receiving fibrous prolongations from this membrane are the aorta, the superior 

 vena cava, the right and left pulmonary arteries, the four pulmonary veins, and the impervious 

 ductus arteriosus. The inferior vena cava enters the pericardium through the central tendon 

 of the Diaphragm, and consequently it receives no covering from the fibrous layer (Fig. 413). 



The serous pericardium -is, as already stated, a closed sac which lines the fibrous pericardium 

 and is invaginated by the heart; it therefore consists of a visceral and a parietal portion. The 

 visceral portion, or epicardium, covers the heart and the great vessels, and from the latter is 

 continuous with the parietal layer which lines the fibrous pericardium. The portion which 

 covers the vessels is arranged in the form of two tubes. The aorta and pulmonary arterv are 

 enclosed in one tube, the arterial mesocardium. The superior and inferior venae cava? and the 

 four pulmonary veins are enclosed in a second tube, the venous mesocardium, the attachment 



