DISSECTION OF THE HEAD AND NECK 225 



In the operation of tracheotomy the incision into the trachea is prefer- 

 ably made between the cricoid cartilage and the isthmus of the thyreoid 

 gland (so-called high operation). 



Muscles of the Neck. 



Study the form, position, insertion, and innervation of the 

 following muscles : 



Those of the Second Layer. 



(a) Digastric muscle (M. digastricus) . 



(b) Stylohyoid muscle (M. stylohyoideus) . 



These are supplied by Nn. cerebrales. 

 Those of the Third Layer. 



(a) Omohyoid muscle (M. omohyoideus) . 



(b) Sternohyoid muscle (M. sternohyoideus) . 



(c) Sternothyreoid muscle (M. sternothyreoideus) . 



(d) Thyreohyoid muscle (M. thyreohyoideus) . 



These are supplied by branches of the Nn. cervicales running 

 in the descending ramus of the N. hypoglossus. 



The Sternoclavicular Joint and the Ligaments about the Clavicle, 



Sternum, and First Rib. 



The dissector of the upper extremity has removed the M. 

 pectoralis major from the clavicle and sternum, and the sterno- 

 clavicular joint (articulatio sternoclavicularis) may now be 

 studied. (Cf. Spalteholz, Fig. 227.) What bony surfaces are 

 here concerned ? Note the following : 



(a) Sternoclavicular ligament (Lig. sternoclaviculare) . 



(b) Interclavicular ligament (Lig. interclaviculare) . 



(c) Costoclavicular ligament (Lig. costoclaviculare) (0. T. rhomboid liga- 



ment). 



Cut through these ligaments and pull the clavicle lateralward 

 so as forcibly to open the Sternoclavicular joint. Observe that 

 the articular disk of fibrocartilage (discus articularis) separates 

 two joint-cavities, each with a special capsule (capsula articu- 

 laris} . 



The Root of the Neck. 



Remove with great care the areolar tissue at the root of the 

 neck, avoiding injury to the finer rami of the sympathetic system. 

 Study the structures on both sides of the body. 



Muscles. 



(a) Anterior , scalene (M. scalenus anterior). 



(b) Middle scalene (M. scalenus medius). 



(c) Posterior scalene (M. scalenus posterior). 



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