536 ABDOMEN 



pleural and peritoneal membranes are merely separated from 

 each other by some loose areolar tissue. Through this gap 

 the superior epigastric branch of the internal mammary 

 artery descends into the abdominal wall. 



Posterior Attachment, The arcus lumbo-costalis lateralis 

 (O.T. ligamentum arcuatum externum) is a fibrous band 

 which stretches from the last rib to the transverse process 

 of the first lumbar vertebra. It arches in front of the 

 quadratus lumborum, and is merely the thickened upper part 

 of the fascia which covers that muscle, i.e. the anterior 



FIG. 2ii. Posterior Surface of the Anterior Wall of the Thorax and 

 Abdomen, to show the Costal and Sternal Origins of the Diaphragm on 

 the left side. (From LUSCHKA'S Anatomy, modified.) 



3. Xiphoid process. 8. Costal origin of diaphragm. 



5. Trans versus thoracis. 



6. Transversus abdominis. 



7. Sternal origin of diaphragm. 



10. Linea alba. 



11. Musculo-phrenic artery. 



lamella of the lumbar fascia. By pressing the rib backwards 

 the arch will be rendered more prominent. The last dorsal 

 nerve passes laterally and downwards under this ligamentous 

 arch. The arcus lumbo-costalis medialis (O.T. ligamentum 

 arcuatum internum) arches over the psoas magnus muscle, 

 and, like the lateral arch, is simply a thickening of the fascia 

 which covers the muscle. It is the stronger of the two, and 

 is attached by one extremity to the tip of the transverse 

 process of the first lumbar vertebra, and by the other to the 

 body of the second lumbar vertebra and the tendinous part 

 of the corresponding crus of the diaphragm. Fleshy fibres 



