692 



HUMAN ANATOMY. 



Fig. 656. 



Position. — The heart may vary considerably in position without being regarded 

 as abnormal, but what may be considered its typical position with reference to the 

 anterior thoracic wall may be stated about as follows : The apex is situated behind 

 the fifth intercostal space, about 8 cm. (3^4^ in.) from the median line, this position 

 beino- median to and slightly below the junction of the fifth costal cartilage with its 

 rib. The level of the base may be approximately indicated by a line drawn from a 

 point slightly above the upper border of the third costal cartilage of the left side, 

 about 4.5 cm, (i^^^ in.) from the median line of the sternum, to a point upon the 

 upper border of the third costal cartilage of the right side, about 3 cm. {\}{ in.) 

 from the middle line. If now the left end of the i)ase-line be united to the apex 

 point by a line which is slightly convex towards the left, and a line, markedly convex 

 towards the right, be drawn from the right end of the base-line to the junction of 

 the se\'enth costal cartilage of the right side with the sternum and thence to the 



apex point, a heart-area will be en- 

 closed which corresponds to the out- 

 line of the organ as seen from in 

 front. 



Considerable importance at- 

 taches to the location of the auriculo- 

 ventricular and aortic orifices with 

 reference to the anterior thoracic wall. 

 The right atiriculo-ventricidar ori- 

 fice in a typical heart lies on a level 

 with the attachment of the fifth costal 

 cartilages to the sternum, almost be- 

 hind the median line of that bone and 

 opposite the fourth intercostal space, 

 while the left auriculo-ventricular 

 orifice is opposite the sternal end of 

 the left third intercostal space. In 

 other words these openings lie along 

 a line which corresponds with the 

 auriculo-ventricular groove, and this 

 may be represented by a line drawn 

 from the upper border of the junc- 



tion of the seventh costal cartilage of 

 the right side with the sternum to the 

 sternal end of the third left costal 

 cartilage. The right orifice is lo- 

 cated upon the line where it is inter- 

 sected by a line joining the sternal 

 ends of the fifth costal cartilages, 

 while the left one is situated at its 

 upper end. 



The systemic and pulmonary 

 aortic orifices are situated at about 

 the level of the attachment of the third costal cartilages to the sternum, the pulmon- 

 ary orifice being behind the sternal end of the third left cartilage, while the aortic 

 orifice is behind the left half of the sternum, a little below and to the right of the pul- 

 monary one, the two orifices overlapping for about one-quarter of their diameters. 

 It is to be noted, however, that the pulmonary aorta is directed upward and to the 

 left, while the systemic aorta inclines decidedly towards the right in the first part of 

 its course; and since the sounds caused by the valves which guard the orifices are 

 carried in the direction of the blood-stream, auscultation of the pulmonary semilunar 

 valves may be practised over the sternal end of the second left intercostal space, 

 while that of the systemic valves is best performed over the sternal end of the second 

 right space. 



Similarly the close proximity of the areas of the left auriculo-ventricular and 

 systemic aortic orifices, as projected upon the thoracic wall, might lead to confusion, 



Position of heart and valves in relation to anterior thoracic 

 wall. A, aortic valve; P, valve of pulmonary aoria ; T, tri- 

 cuspid valve ; M, mitral valve. 



