THORACIC WALL 7 



cutaneous are the medial branches of the posterior rami of 

 the upper six thoracic nerves and the lateral branches of 

 the posterior rami of the lower six; the lateral branches 

 of the anterior rami and the anterior ends of the anterior 

 branches. 



The cutaneous branches of the posterior rami have 

 already been removed by the dissectors of the extremities, 

 but the dissector of the thorax will find remnants of the 

 lateral and anterior branches of the anterior rami of the 

 thoracic nerves on the lateral and anterior aspects of the wall 

 of the thorax where they appear as lateral and anterior 

 cutaneous nerves. 



The upper six anterior cutaneous nerves on each side, 

 the accompanying perforating branches of the internal 

 mammary artery, and the lateral cutaneous nerves which have 

 been left in position by the dissectors of the superior extremity 

 and the abdomen, together with portions of certain muscles 

 of the superior extremity and the abdominal wall which are 

 still attached to the thoracic wall, must be identified and 

 examined before the dissection of the thoracic wall is 

 commenced. 



The anterior cutaneous nerves and the perforating branches 

 of the internal mammary artery will be found at the sternal 

 ends of the intercostal spaces piercing the pectoralis major. 

 The lateral cutaneous nerves lie along the mid-axillary line, 

 where they appear between the digitations of the serratus 

 anterior and the obliquus externus. 



The remnants of muscles to be examined are, from before 

 backwards, the pectoralis major, attached to the sternum and 

 the cartilages of the upper six ribs ; the pectoralis minor, 

 attached to the sternal extremities of the bony parts of the 

 third, fourth, and fifth ribs ; and the serratus anterior, attached 

 to the upper eight or nine ribs, along a line extending from 

 the anterior to the posterior axillary margin. Towards the 

 lower margin of the chest lie : the rectus abdominis, attached 

 to the xiphoid process and the cartilages of the fifth, sixth, 

 and seventh ribs ; the obliquus externus, attached to the lower 

 eight ribs, interdigitating with the serratus anterior and the 

 latissimus dorsi ; and the latissimus dor si, attached to the lowest 

 three or four ribs. 



Dissection. After their attachments have been verified 

 remove the remnants of the muscles of the superior extremity 



