206 APPLIED ANATOMY. 



The tricuspid valve lies in the middle of the sternum opposite the fourth 

 intercostal space. It runs obliquely downward and to the right from the third left 

 intercostal space to the fifth right costal cartilage. It separates the right atrium and 

 ventricle. 



The pulmonary semilunar valve lies opposite the sternal end of the third left 

 costal cartilage. It is the most superficial valve and the one highest up on the ster- 

 num. It prevents regurgitation of the blood into the right ventricle from the lungs. 



The aortic semilunar valve lies under the left side of the sternum about level 

 with the lower edge of the third costal cartilage. It is just below and to the right of 

 the pulmonary valve, and above and to the left of the bicuspid valve. 



LOCATION OF VALVULAR SOUNDS. 



The sounds produced by the closure of the valves do not correspond with the 

 position of the valves, but are as follows. 



The bicuspid sound is heard most distinctly at the apex of the heart as far 

 inward as the parasternal line and as high as the third interspace. It is transmitted 

 around the chest toward the axilla. 



The tricuspid sound is best heard at the left sternal border between the fifth 

 and sixth costal cartilages (Tyson). 



The pulmonary sound is best heard in the second interspace to the left of the 

 sternum; the cartilage above is called the pulmonary cartilage. 



The aortic sound is best heard in the second right intercostal space and the 

 cartilage above is called the aortic cartilage. The aortic sounds are transmitted up 

 the neck in the direction of the great blood-vessels. 



VARIATION IN SIZE AND POSITION OF THE HEART. 



The heart becomes enlarged both by being dilated and by being hypertrophied, 

 usually both conditions are present; and its position is often changed by disease both 

 of itself and of adjacent organs. It is apt to enlarge unequally. In emphysema and 

 bicuspid regurgitation the right side becomes enlarged, the pulmonary .circulation 

 being impeded. In aortic disease, arteriosclerosis, muscular exertion, or any cause 

 impeding the course of the blood through the arteries there is produced an enlarge- 

 ment of the left side of the heart. 



The average weight of the healthy heart is in the male 280 Gm. (9 oz. ), and in 

 the female 250 Gm. (8 oz. ). These may be doubled in cases of enlargement. 

 When the heart is enlarged the apex beat changes its position; it may occupy the 

 sixth, seventh, or eighth interspace instead of the fifth, and may be as far as 5 to 7.5 

 cm. (2 to 3 in. ) to the left of the nipple line. 



When it enlarges upward, instead of the absolute dulness beginning opposite the 

 fourth costal cartilage, it is opposite the third or even the second interspace. Toward 

 the right side the absolute dulness may extend a couple of centimetres beyond the 

 right edge of the sternum, instead of being near its left edge as is normal. 



The heart is readily displaced by pressure from the surrounding structures. If 

 there is abdominal distention by gas or ascites, or if the liver or spleen is enlarged, 

 the heart is pushed upward. Enlargement of the liver may likewise depress the 

 heart, if the patient is in an upright position, by the weight of the liver dragging it 

 down. Aneurisms of the arch of the aorta, tumors, or emphysema may also depress 

 it. In the aged the apex beat may be normally in the sixth interspace. 



Lateral displacement occurs in cases of pleural effusion. Osier says (" Pract. of 

 Med. ," p. 594), this is not due to a twisting of the heart* on its axis but to a positive 

 lateral dislocation of the heart and pericardium. Pneumothorax or tumors on one side 

 may also push the heart toward the opposite side. It may be pulled to one side by 

 pleural adhesions and in those cases of fibroid phthisis in which the lung becomes 

 markedly retracted. Abscess or tumors of the mediastinum also displace it. 



The position of the pulsation of the heart is not always an indication of the posi- 

 tion of the apex. In pleural effusion the pulsation may be one, two, or three inter- 

 spaces higher than normal, while the apex itself may not be elevated. 



