872 



THE VASCULAE SYSTEM. 



The base is limited below by the inferior part of the coronary sulcus, in which 

 the coronary sinus lies; its upper border is in relation with the pulmonary 

 arteries. A fold of pericardium, the vestigial fold, descends, near the left border 

 of the base, from the left branch of the pulmonary artery, above, to the left superior 

 pulmonary vein below. It contains the ligamentum v. cavse sinistrse, and from 

 its lower end a small vein, the oblique vein of the left atrium, passes below the 

 orifice of the lower left pulmonary vein, and descends to the coronary sinus. 

 Further, it is from the base that the visceral layer of the pericardium, which 

 elsewhere completely invests the heart, is reflected to the fibrous layer, the lines of 

 reflection corresponding with the orifices of the great vessels. 1 



Left atrium 



Pulmonary artery 



Superior vena 

 cava 



Right coronary 

 artery 



Right auricle 



Right coronary 

 artery 



Anterior ventri- 

 cular artery 



-Left auricle 



Right marginal 

 artery 



Circumflex branch of left 

 coronary artery 



Interventricular branch of left 

 coronary artery 



Left ventricle 



Left marginal 

 artery 



Right ventricle 



FIG. 751. THE STERNO-COSTAL SUEFACE OF FORMALIN-FIXED HEART. 



The apex, bluntly rounded, is formed entirely by the left ventricle. It is 

 directed downwards, anteriorly, and to the left, and is situated, under cover of 

 the anterior borders of the left lung and pleura, behind the fifth left intercost 

 space, three and a half inches from the anterior median line. 



The diaphragmatic surface is formed by the ventricular part of the heart. It 

 rests upon the diaphragm, chiefly on the central tendon, but, upon the left side, on 

 a small portion of the muscular substance also, and it is divided into two 

 a smaller to the right side and a larger to the left side by an oblique antero- 

 posterior groove, the inferior interventricular sulcus. It is separated from the base 

 by the posterior or inferior portion of the coronary sulcus. 



The sterno-costal surface is directed upwards, anteriorly, and to the left. II 

 lies posterior to the body of the sternum and the medial extremities of th< 

 cartilages of the third, fourth, fifth, and sixth ribs of the right side, and 

 greater extent of the corresponding cartilages of the left side. This surfa 

 is separated into upper and lower sections by the anterior portion of th< 



1 In the foetus and young child the atrial portion of the heart forms not only the base, but also 

 posterior part of the inferior or diaphragmatic surface. 



