380 



The Heart. 



'l]- 

 I h 



Lunula valvulae seiuilunaris 



Septum meinbranaceum ventriculoruni 

 A. coronaria [cordisl dextra 



Nodulus valvulae semilunaris [Arantii] 



Valvula semilunaris posterior 



A. coronaria ] cordis] sinistra 



Valvula 



semilunaris 



dextra 



Septum 



musculare 



ventriculoruni 



Valvula semilunaris 

 sinistra 



Cuspis anterior 



valvulae bicuspi- 



dalis fmitralisj 



Mvocardiuni 



426. Valvulae semilunares aortae, opened up. 



(The left ventricle and the aorta have heen opened hy a cut passing between the right and the 



left valve; the walls have been spread apart.) 



The TCntriculus sinister fief I ventricle) (see Figs. 411 421 and 425) has the shape 

 of an egg, the large end of which is directed toward the right and backward and contains the 

 ostia venosmn et arteriosmn ; the other end forms the apex of the heart. As regards the inner 

 surface see also p. 371. The ostium venosum is guarded by the valvula bicuspidalis [jnitralix] 

 (bicuspid or mitral valve). This consists of two large cusps and usually two small intermediary 

 cusps : of the larger cusps, the cuspis posterior, situated to the left and behind, arises from 

 the annulus fibrosus sinister; the cuspis antei'ior, situated to the right and in front, conies 

 however only partially from the annulus fibrosus sinister, having its origin chiefly from that 

 connective tissue portion of the root of the aorta which extends between the trigona fibrosa, 

 S(j that the ventricular surface of this cusp goes over directly into this-part of the wall of the 

 aorta (see also Figs. 420 and 425). The chordae tendineae come from two papillary muscles, 

 each of which caii in turn be divided into several wedges; both muscles are developed from the lett 

 wall and correspond in their position approximately to the intermediary cusps. The ostium arterio- 

 sum contains the valvulae semilunares aortae dextra, sinistra, poste?-ior: the posterior portion 

 of the left valve and thi' postcrinr valve arise from the membranous part of the root of the aorta. 



Each valvula semilunaris presents just below the middle of its concave free margin 

 a small nodular thickening, nodulus valvulae semilunaris [Arantii], and on both sides of 

 this, near the margin, a sickle-shaped, thinner portion, lunula valvulae semilunaris, by means 

 of which it lies against the neighboring valve. 



The small or pulniouary circulation consists of the a. pulmonalis, the vv. pulmonales 

 and their branches. 



The a. pulmonalis (see Figs. 411-413, 427, 62S and 029) extends on the left side of 

 the aorta ascendens obli([uely to the left and backward and divides below the arcus aortae uito 

 a ramus dexter and a ramus sinister. The former goes below the arcus aortae behind the 

 aorta ascendens and v. cava su})erior, in front of the bronchus dexter to the hilus of the right 

 lung; the r. sinister runs in front of the bronchus sinister and the aorta thoracaUs to the left 

 lung. In the prolongation of the main stem a band of elastic connective tissue, the ligainentum 

 arteriosum, extends to tlie concave anterior wall of the end of the arcus aortae. 



The vv. pulmonales (see Figs. 427, 619, 620, 628 and 629) come from the hilus pul- 

 monalis on each side and open into the atrium sinistrum. They run on both sides in front of 

 the main branches of the a. ])ulm(inalis and in front of th(> bronchi; in addition the right veins 

 go behind the v. cava superior and the atrium dextrimi, the left in front of the aorta thoracahs. 



