THE HEART 



527 



ventricular groove}; this contains the trunks of the nutrient vessels of the heart, 

 and is deficient in front, where it is crossed by the root of the pulmonary artery. 

 The interatrial groove, separating the two atria, is scarcely marked on the posterior 

 surface, while anteriorly it is hidden by the pulmonary artery and aorta. The 

 ventricles are separated by two grooves, one of which, the anterior longitudinal 

 sulcus, is situated on the sternocostal surface of the heart, close to its left margin, 

 the other posterior longitudinal sulcus, on the diaphragmatic surface near the right 

 margin ; these grooves extend from the base of the ventricular portion to a notch, 

 the incisura apicis cordis, on the acute margin of the heart just to the right of the 

 apex. 



Cut edge of pericardium 



FIG. 490. Front view of heart and lungs. 



The base (basis cordis) (Fig. 491), directed upward, backward, and to the right, 

 is separated from the fifth, sixth, seventh, and eighth thoracic vertebrae by the 

 esophagus, aorta, and thoracic duct. It is formed mainly by the left atrium, 

 and, to a small extent, by the back part of the right atrium. Somewhat quadri- 

 lateral in form, it is in relation above with the bifurcation of the pulmonary artery, 

 and is bounded below by the posterior part of the coronary sulcus, containing the 

 coronary sinus. On the right it is limited by the sulcus terminalis of the right 

 atrium, aiid on the left by the ligament of the left vena cava and the oblique vein 

 of the left atrium. The four pulmonary veins, two on either side, open into the 

 left atrium, while the superior vena cava opens into the upper, and the anterior 

 vena cava into the lower, part of the right atrium. 



The Apex (apex cordis). The apex is directed downward, forward, and to the 

 left, and is overlapped by the left lung and pleura: it lies behind the fifth left 

 intercostal space, 8 to 9 cm. from the mid-sternal line, or about 4 cm. below and 

 2 mm. to the medial side of the left mammary papilla. 





