Outlines of human physiology . parts. 1, Of a cen- being alternately enlarged and diminished. 59 tral thin tendon of the shape of a trefoil leaf, of greaterbreadth than depth, which, although in a degree con-cave downwards, yet may be regarded as spread outhorizontally at the level of the ninth dorsal vertebra, orof the lowest part of the fifth rib. 2. Of muscularfibres derived from the anterior and lateral margins ofthe central tendon, which slope downwards to be insertedinto the ensiform cartilage and into the inner and lowerpart of the seven lowest ribs, and are called the greatermuscle of
Outlines of human physiology . parts. 1, Of a cen- being alternately enlarged and diminished. 59 tral thin tendon of the shape of a trefoil leaf, of greaterbreadth than depth, which, although in a degree con-cave downwards, yet may be regarded as spread outhorizontally at the level of the ninth dorsal vertebra, orof the lowest part of the fifth rib. 2. Of muscularfibres derived from the anterior and lateral margins ofthe central tendon, which slope downwards to be insertedinto the ensiform cartilage and into the inner and lowerpart of the seven lowest ribs, and are called the greatermuscle of the diaphragm. 3. Of other muscular fibreswhich descend from the posterior edge of the centrumtendinosum to the lumbar vertebrse, and are called thelesser muscle. The diaphragm gives height by its ac-tion to the cavity of the chest. In an ordinary inspi-ration, the lateral parts, or the greater muscle, alonesensibly descend, something in the manner, but not tothe degree represented by the dotted lines in the ad-joined 60 Contents of the Chest. Except during the deepest inspiration, the lungs donot reach lower than the sixth rib in front, and theeighth dorsal vertebra behind ; laterally below this level,the diaphragm lies in contact with the ribs, or ratherthe pleura diaphragmatica with the pleura diaphragm gives passage to different vessels andnerves; and it is remarkable, that while the oesopha-gus, the aorta, and thoracic duct pass through mus-cular apertures, the pressure of which they are calcu-lated to resist or to profit by, the great ascending ve-nous trunk passes through an opening in the centraltendon, with the margin of which its substance is in-terwoven, so that the vein is held open by the wholetonic force of the greater and lesser muscle. The abdominal muscles are the antagonists of thediaphragm, which upon becoming relaxed admits ofbeing raised through their lateral pressure upon thebowels. In the cavity of the chest, thus amply furnished wit
Size: 1418px × 1763px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookidoutlinesofhumanp00, booksubjectphysiology
