204 THE POCKET ANATOMY 



Mitral. Opposite junction of 4th left costal cartilage with 

 sternum. 



Divisions. The heart is divided longitudinally by a septum 

 into two halves, right and left, each of which is subdivided 

 transversely into two cavities. Those four divisions are 

 indicated on the heart's surface by grooves. Two longitudinal 

 grooves, one situated on the anterior and the other on the 

 posterior surface, indicate the lateral division, whilst a trans- 

 verse furrow, the auricula-ventricular groove, indicates its separa- 

 tion into auricles above the furrow and ventricles below it. 



The Circulation. The right auricle receives venous blood 

 from the vense cavae and coronary sinus ; thence it passes 

 into the right ventricle, whence it is conveyed to the lungs by 

 the pulmonary artery. After being oxygenized the blood 

 passes into the left auricle by the pulmonary veins ; thence it 

 is conveyed into the left ventricle, and from there to the aorta, 

 whence it passes through the body. 



THE CAVITIES OF THE HEART. 



The RIGHT AURICLE consists of a principal cavity and an 

 appendix auriculae. 



The principal cavity, or sinus venosus, is of an irregular 

 form. 



The appendix auricula is a small muscular pouch projecting 

 from the anterior and upper angle of the auricle overlapping 

 the root of the pulmonary artery. 



At the junction externally of the two cavities is seen a 

 well-marked groove (sulcus terminalis), which on the interior 

 appears as a ridge (crista terminalis of His) . 



Openings in the sinus. Superior vena cava, in the upper 

 and front part. Inferior vena cava, at the lower and back 

 part of the auricle. Between the openings of the two cavae is 

 a muscular projection, the tubercle of Lower. 



The coronary sinus opens between the inferior vena cava and 

 the auric ulo-ventricular opening. 



Foramina Thebesii are the mouths of small cardiac veins. 



The auricula-ventricular opening is in front of the inferior 

 cava. 



Openings of anterior cardiac veins (2 or 3) from the surface of 

 the right ventricle. 



Valves. The Eustachian valve is a semilunar fold of endo- 

 cardium in front of the anterior margin of the inferior vena 

 cava ; passes upwards and to the left to anterior margin of 

 annulus ovalis. 



