98o 



A MANUAL OF ANATOMY 



The pulmonary valve guards the orifice of the pulmonary artery, 

 and prevents regurgitation of blood from the trunk of the pulmonary 

 artery into the right ventricle during the elastic recoil of the arterial 

 wall. It is composed of three semilunar or sigmoid segments, 

 and the wall of the artery, opposite each segment, presents a recess, 

 these recesses being called the sinuses of Valsalva. The valve and 

 the sinuses of Valsalva are similar to corresponding structures in 

 connection with the aortic orifice, and will be fully described along 

 with that orifice. 



Interior of the Left Auricle. — ^The musculi pectinati are present 

 only in the auricular appendix, whereas in the right auricle they are 



Pulmonary Artery 

 , Lunula 



^^Pulmonary Veins 



Ascending Aorta (opened) - 



Aortic Seniilunar Valves 



Interventricular 

 Septum 



-Chordae Tendinex 



— Musculus Papillaris 



Columnje Carneae 



Fig. 401. — The Interior of the Left Auricle and Left Ventricle. 



present both in the auricular appendix and on the right wall of the 

 atrium. The wall of the left atrium is entirely smooth. The atrium 

 presents five openings, namely, the openings of the four pulmonary 

 veins, and the auriculo-ventricular opening. 



The orifices of the four pulmonary veins are situated on the pos- 

 terior wall at either side, two right and two left, and they are 

 destitute of valves. 



The auriculo-ventricular, or mitral, orifice is situated in the anterior 

 part of the floor of the atrium. It is oval, and, in health, it admits 

 two fingers held side by side, and in close contact. 



V'ence minimce cordis arc said to open into the left auricle. 



