1 66 Anatomy Applied to Medicine and Surgety. 



Relations. The structures above the diaphragm 

 and in contact with it, are: The pleurae and the pericar- 

 dium, the latter being adherent to the central tendinous 

 portion and to some of the adjacent muscular tissue. Be- 

 low, the concave surface of this structure is in relation 

 with the liver, the stomach, the pancreas, the spleen, the 

 kidneys and the suprarenal capsules, and is covered for the 

 most part by the peritoneum. 



Actions. The contraction of the diaphragm the 

 result of the flattening of its arched fibres causes an in- 

 crease in the vertical diameter of the thorax, with a cor- 

 responding diminution in the vertical diameter of the ab- 

 domen. The diaphragm is an important muscle in inspi- 

 ration, since, in addition to increasing the capacity of the 

 thorax in the manner mentioned above, it enlarges it later- 

 ally through elevation of the lower ribs by the contraction 

 of those fibres which, arising from the central tendon, 

 act from above, i.e., from this central tendon. In the de- 

 scent of the diaphragm the whole muscle does not move 

 down uniformly, because the support given to the middle 

 portion of the central tendon by the cervical fascia, pre- 

 vents the central tendon from being depressed as much as 

 the lateral portions, hence, the right side of the diaphragm 

 is depressed about one inch, the left side about four-fifths 

 of an inch and the central portion about two-fifths of an 

 inch, in inspiration. 



Landmarks. The convexity of the diaphragm is 

 especially marked on the right side, since the position and 

 shape of the liver raise it up in this situation so much that 

 its upper limit, in ordinary expiration, reaches the level of 

 the junction of the fifth costal cartilage with the sternum. 

 Viewed from the side, this point corresponds to the level 

 of the sixth and seventh ribs, while from behind, it corre- 

 sponds to the level of the eighth rib. The left half of the 



