DISSECTION OF THE THORAX 



WALLS AND VISCEEA OF THOKAX. 



BEFOKE beginning the dissection of the thorax, the student 

 should review the thorax in the articulated skeleton. Examine 



(a) Cavity of thorax (cavum thoracis). 



(b) Superior aperture of thorax (apertura thoracis superior) (0. T. 



inlet of thorax). 



(c) Inferior aperture of thorax (apertura thoracis inferior] (0. T. outlet 



or base of thorax). 



(d) Costal arches (arcus costarum}. 



(e) Intercostal spaces (spatia intercostalia) . 



(f) Infrasternal angle (angulus infrasternalis) . 



(g) Pulmonary groove (sulcus pulmonalis). 



Thoracic Walls. 



The dissector of the upper extremity and the dissector of the 

 abdomen will have left certain structures still attached to the 

 walls of the thorax. Of these should be noticed the Mm. pec- 

 toralis major, pectoralis minor, serratus anterior, rectus abdorni- 

 nis, obliquus externus abdominis, latissimus dorsi, subclavius, 

 scalenus posterior ; remove all these except the M. scalenus pos- 

 terior, and so expose completely the arcus costarum and the Mm. 

 intercostal es. Preserve, however, the rami cutanei laterales and 

 rami cutanei anteriores of the Nn. intercostales, as well as the 

 perforating rami of the A. mammaria interna. 



Intercostal Muscles (Mm. intercostales). 



Clean carefully and study the form, position, origin, inser- 

 tion, action, and innervation of the 



(a) External intercostal muscles (Mm. intercostales externi). 



(Observe anteriorly the external intercostal ligaments (ligamenta 

 intercostalia externa) (0. T. anterior intercostal membrane).) 



(b) Internal intercostal muscles (Mm. intercostales interni). 



Bring them into view by dividing in all the spaces the Mm. 

 intercostales externi and Ligg. intercostalia externa along their 

 inferior margins and reflecting them upward. Avoid in.jury to the 

 Aa. intercostales. Observe the internal intercostal ligaments (liga- 

 menta intercostalia interna) (0. T. posterior intercostal mem- 

 branes). 



399 



