118 



RESPIRATION RESPIRATORY MOVEMENTS. 



FIG. 46. Diaphragm (Sappey). 



1, 2. 8, central tendon ; 4, right pillar ; 5, left pillar ; 6, 7, processes between the pillars ; 8, 8. openings 

 for the splanchnic nerves ; 9, fibrous arch passing over the psoas magnus ; 10, fibrous arch passing 

 over the quadratus lumborum ; 11, muscular fibres arising from these two arches ; 12, 12. muscular 

 fibres arising from the lower six ribs ; 13, fibres from the ensiform cartilage ; 14, opening for the 

 vena cava ; 15, opening for the oesophagus ; 16, opening for the aorta ; 17, 17, part or the transver- 

 salis muscle ; 18, 18, aponeurosis ; 19, 19, quadratus lumborum ; 20, 20, psoas magnus ; 21, fourth 

 lumbar vertebra. 



Action of tlie Diaphragm. The descriptive and general anatomy of the 

 diaphragm gives a pretty correct idea of its uses in respiration. It arises 



from the border of the lower circumfer- 

 ence of the thorax and mounts into the 

 cavity of the chest, forming a vaulted 

 arch, or dome, with its concavity toward 

 the abdomen and its convexity toward 

 the lungs. In the central portion, there 

 is a tendon of considerable size and shaped 

 something like the club on a playing- 

 card, with middle, right and left leaflets. 

 The remainder of the organ is composed 

 of radiating fibres of striated muscular 

 tissue. The oesophagus, aorta and infe- 

 rior vena cava pass through the dia- 

 phragm from the thoracic to the abdom- 

 inal cavity, by three openings. 



The opening for the oesophagus is sur- 

 rounded by muscular fibres, by which it 

 FIG. 47.-^ c <ion of the diaphragm in inspira- is partially closed when the diaphragm 



Vertical sectiontnrou second rib on the Contracts ill inspiration, as the fibres 



simply surround the tube and none are 

 attached to its walls. 



