The Structure of Pericardium

Structure of the Pericardium
The pericardium is a fibro-serous membrane, and consists, therefore of two layers, an external fibrous and an internal serous.

The fibrous layer is a strong, dense membrane. Above, it surrounds the great vessels arising from the base of the heart, on which it is continued in the form of tubular prolongation which are gradually lost upon their external coat, the strongest being that which encloses the aorta. The pericardium may be traced over these vessels, to become continuous with the deep layer of the cervical fascia. In front the pericardium is connected to the posterior surface of the sternum by two fibrous bands, the superior and interior sterno pericardiae ligaments, the upper passing to the manubrium, and the lower to the ensiform cartilage. On each side of the ascending aorta it sends upward a diverticulum: the one on the left side, somewhat conical in shape, passes upward and outward, between the erch of the aorta and the pulmonary artery, as far as the ductus arteriousus, where it terminates in a eaecal extrememity, which is attached by loose connective tissue to the obliterated duet. The one on the right side passes upward and to the right, between the ascending aorta and vena cava superior, and also terminates in a caeval extremity. Below, the fibrous layer is attached to the central tendon of the Diaphragm, and on the left side to its muscular fibres.

The vessels receiving fibrous prolongations from this membrane are the aorta, the superior vena cava, the right and left pulmonary arteries, and the four pulmonary veins. As the inferior vena cava enters the pericardium through the central tendon of the Diaphragm, it receives no covering from the fibrous layer.

The serous layer invests the heart, and is then reflected on the inner surface of the pericardium. It consists, therefore of a visceral and parietal portion. The former invest the surface of the heart, and the commencement of the great vessels, to the extent of an inch and a half from their origin; from these it is reflected upon the inner surface of the fibrous layer, lining, below, the upper surface of the central tendom of the Diaphragm. The serous membranes encloses the aorta and pulmonary artery in a single tube, so that a passage, termed the transverse sinus of the pericardium, exist between these vessel in front and the auricles behind.