A system of human anatomy, general and special . nsiform cartilage and the cartilages ofthe adjoining ribs, is a small triangular space where the muscularfibres of the diaphragm are deficient. This space is closed only byperitoneum on the side of the abdomen, and by pleura within thechest. It is therefore a weak point, and a portion of the contents ofthe abdomen might, by violent exertion, be forced through it, pro-ducing phrenic, or diaphragmatic hernia. The lesser muscle of the diaphragm takes its origin from the bodiesof the lumbar vertebras by two tendons. The right, larger andlonger than
A system of human anatomy, general and special . nsiform cartilage and the cartilages ofthe adjoining ribs, is a small triangular space where the muscularfibres of the diaphragm are deficient. This space is closed only byperitoneum on the side of the abdomen, and by pleura within thechest. It is therefore a weak point, and a portion of the contents ofthe abdomen might, by violent exertion, be forced through it, pro-ducing phrenic, or diaphragmatic hernia. The lesser muscle of the diaphragm takes its origin from the bodiesof the lumbar vertebras by two tendons. The right, larger andlonger than the left, arises from the anterior surface of the bodies ofthe second, third, and fourth vertebrae ; and the left from the side of thesecond and third. The tendons form two large fleshy bellies {crura),which ascend to be inserted into the central tendon. The inner fas-ciculi of the two crura cross each other in front of the aorta, andagain diverge to surround the cesophagus, so as to present the appear- 20* 234 MUSCLES OF THE ABDOMEN. Fig. 114*. ance of a figure of eight. The anterior fasciculus of the decussationis formed by the right crus. The openings in the dia-phragm are three: one,qua-drilateral, in the tendinouscentre, at the union of theright and middle leaflets,for the passage of the in-ferior vena cava; a muscu-lar opening of an ellipticshape formed by the twocrura, for the transmissionof the (esophagus and pneu-rnogastric nerves; and athird, the aortic, which isformed by a tendinous archthrown from the tendon ofone crus to that of the other,beneath which pass the aor-ta, the right vena azygos, andthoracic duct. The greatsplanchnic nerves passthrough openings in the lesser muscle on each side, and the lessersplanchnic nerves through the fibres which arise from the ligarnen-tum arcuatum internum. Relations.—By its superior surface with the pleurae, the pericardium,the heart, and the lungs. By its inferior surface with the peritoneum ;on the left with the stomach and
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectanatomy, bookyear1847
