238 ANATOMY IN A NUTSHELL. 



Blood Supply. — Internal mammary arteries through its sternal and per- 

 foratum branches, also twigs from the aortic intercostal arteries. 



Heart. 



The covering of the heart is called the Pericardium. Besides covering the 

 lu ait it encloses the origin of the great vessels. It is situated behind the sternum 

 from the third to the seventh costal cartilages (inclusive) and between the two 

 pleurae. It forms a closed sac. the base of which is attached to the central 

 tendon and adjoining muscular substance of the Diaphragm, and it extends 

 more to the 1< ft than to the right. The apex of the pericardium is directed up- 

 ward and surrounds the great vessels for about two inches. Behind the per- 

 icardium are (1) the two bronchi. (2) the esophagus, (3) descending aorta. In 

 front are f 1 ) the margin of the lungs, (2) remains of the thymus gland (above), 

 (3) areolar tissue (below). (4) the sternum. On the sides it is covered by the 

 pleura and the phrenic nerve. 



The pericardium is composed of two layers, first a fibrous, second a serous. 

 Tin: fibrous OB external layer is strong and dense. It sends prolongations 

 around the gr< at vessels which join their external coats. It also sends a diverti- 

 culum upward on each side of the ascending aorta. The one on the left side of 

 the ascending aorta passes between the left pulmonary artery and the arch of 

 the aorta to the ductus arteriosus where it ends in a blind extremity. The one 

 on the light side of the ascending aorta passes between this vessel and the super- 

 ior vena cava, and it also ends in a blind extremity. This fibrous layer is at- 

 tached below to the central tendon and muscular substance of the Diaphragm. 

 Two ligaments, the superior sterno-pericardial and the inferior sterno-peri- 

 cardial, connect it with the sternum anteriorly. 



Tin. serous ok internal layer consists of two portions, first a visceral, 

 and second a paiital. The visceral layer covers the heart and the great v< ssels 

 for about an inch and a half and then is reflected upon the inner surface of the 

 fibrous layer forming the parietal portion. The pulmonary artery and the 

 aorta are enclosed in a single tube of pericardium. Behind this tube there is a 

 passagi called the transv< rse p< ricardial sinus. The pericardium only partially 

 covers the vena cava and pulmonary veins, so that on each si le of these struc- 

 tures iIk re i- a cul-de-sac. The one on the left side is known as the oblique 

 .-iin s, the one (.n the righi as the straight sinus. The vestigial fold of Marshall 

 lies between the left pulmonary artery and the subadjacent pulmonary vein, 

 thus enclosing the remains of the lefl superior vena cava. This left superior 

 vena cava is a fibrous cord which may be traced upward te> the left superior 

 intercostal vein and downward to the coronary sinus and known as the oblique 

 v< in of Marshall. 



Blood Supply. — The art< ri< s to the pericardium come from the descending 

 thoracic aorta and the internal mammary with its musculo-phrenic branch. 



Nerve Supply. Xerxes to the pericardium are from the tenth, phrenic, 

 and sympath) tic. The' nerve supply to the pericardium, the heart, the pleurae, 

 and the lungs, is derived from these three sources. As said above' they all go 

 tei the | ( ricardium. The- tenth, the sympathetic and pe>ssibly the phrenic pass 



