376 



The Heart. 



Aorta ascendens 



Auricula dextra 



Conus arteriosus 



Arteria pulmonalis 



Vena cava superior 



Crista terminalis 



Sinus venarum, ^ 

 [cavaruml 



Basis cordis -V 



Venae 

 pulinonales< 

 dextrae 



Atrium 



sinistrum 



Tubcrculum 



intervenosum 



[Loweri 



Limbus fossae 

 ovalis [Vieusseuii 



Fossa ovalis 



Yentriculus dexter 



Vena cava inferior 



\ Musculi pectinati 



Ostium venosum ventriculi dextri 



Valvula venae cavae [inferioris, Eustachiii\ \ Valvula sinus coronarii [Thebesii] 



422. Right fore-chamber (atrium dexlrum) 



of a markedly distended adult heart, viewed from the right. 



(A part of the wall of the atrium has heen removed.) 

 The atrium dextrum (right fore- chamber, 0. T. right auricle) (see also Figs. 4 11 -114 

 and 420) is of the shape of an irregular short cylinder. A groove, variably developed, running 

 perpendicularly over the posterior e.xternal surface, the sulcus terminalis atrii dextri, and a 

 ridge on the corresponding spot of the inner wall, the crista terminalis, mark off a posterior, 

 medial portion, the sinus oenarvm [cuvarum] which is derived from a part of the sinus reuniens 

 of the embryonic heart (see also p. 3S4). It contains in its lower and upper walls the mouths 

 of the v. cava superior and inferior and in general has smooth walls. Between the opening of 

 the V. cava inferior and the sidcus coronarius to the left of the sulcus terminalis there is often 

 visible on its outer surface an irregular lumpy projection (appendix auricularis posterior). 

 The posterior wall of the sinus is bounded partly by the atrium sinistrum, being slightly shoved 

 forward by the same and presents there a transverse ridge, the tuberculum intervenosum [Loweri] 

 (0. T. tubercule of Lower). The left wall is formed by the septum atriorum (0. T. interauricular 

 septum), which consists partly of muscle, partly (pars memhranacea septi atriorum) of pure 

 connective tissue. The latter spot lies in the lower part of the wall, is somewliat deepened 

 (fossa ovalis) and is surrounded in front and above by a strong ridge of muscle (limbus fossae 

 ovalis (Vieusseuii IJ. Starting at the anterior limb of the limbus, and arising from the inferior 

 wall, is a thin, often partially perforated, fold of connective tissue which surrounds the mouth 

 of the V. cava inferior from in front and sometimes also from the riglit (valvula venae cavae 

 [inferioris, Eustachii] (0. T. Eustachian valve). .Tust in front of it, in the angle between 

 the inferior, left and anterior walls, lies the mouth of the sinus coronarius ; it is only imperfectly 

 closed from below by the sickleshaped valvula sinus coronarii [ Thebesii] (0. T. coronary valve 

 or valve of Thebesius), whicii is often perforated. The anterior wall of the atrium contains 

 the ostium venosum of the right ventricle. The right wall presents niuuerous muscular ridges 

 projecting on the inner surface (musculi pectinati) (see also Fig. 420) ; these arise from the 

 crista terminalis and ext>nd ap]iriiximately in the direction of the long axis of the heart as 

 far as the sulcus coronarius; between them the wall is translucent when the heart is distended. 



