22 



OUTLINES OF ANATOMY. 



General Description. 



Inferior Carotid or Tracheal Triangle. As this triangle is gradually 

 opened up the following structures will come into view : 



1. The sterno-hyoid and sterno-thyroid muscles. 



2. The branches from the ansa hypoglossi to these muscles. 



3. The external laryngeal nerve. 



4. The superior thyroid artery. 



5. The greater part of the larynx, the thyroid body, and the trachea. 



6. The cjesophagus on the left side. 



7. The recurrent laryngeal nerve. 



When the fascia is removed from this part of the anterior triangle, the only struc- 

 tures which are seen within its limits are the sterno-hyoid and sterno-thyroid muscles. 

 As the dissection is proceeded with, however, the large nerve of supply for these 

 muscles, which comes from the ansa hypoglossi, will be found lying near the outer 

 border of the sterno-thyroid and breaking up into numerous twigs. Toward the 

 upper part of the space the superior thyroid artery will be noticed passing downward 

 under cover of the omo-hyoid, sterno-thyroid, and sterno-hyoid muscles to reach 

 the thyroid body. At a slightly higher level than this artery, the external laryngeal 

 nerve runs forward to end in the crico-thyroid muscle. Under cover of the sterno- 

 hyoid and sterno-thyroid muscles will be observed the larynx, the isthmus and a 

 considerable part of the lateral lobe of the thyroid body, and the trachea. The 

 recurrent laryngeal nerve lies deeply. It will be found in the interval between the 

 gullet and the trachea. As the oesophagus inclines to the left behind the trachea, it 

 follows that it is only seen, when in its natural position, in the left inferior carotid 

 or tracheal triangle. 



Superior Carotid Triangle. During the dissection of the superior carotid 

 triangle the following parts are displayed: 



1. Common carotid dividing into external and internal carotid arteries. 



2. Superior thyroid. ] 



3 ' FacfaT 1 '" Branches of the external carotid. 



5. Occipital. 



Arteries, \ 



Veins. 





Nerves. -| 



6. Ascending pharyngeal. 



7. Hyoid. -j 



8. Sterno-mastoid. \ Branches of the superior thyroid. 



9. Superior laryngeal. i 



10. Sterno-mastoid branch of the occipital. 



1. Internal jugular. 



2. Facial. "1 



5. Anterior temporo-maxillary. ; rr, , r , u 



4. Lin ual r Tributaries of the internal jugular. 



5. Superior thyroid. 



1. Hypoglossal. Crossing the space in a transverse direction. 



2. Descendens hypoglossi. ] 



3. Nerve to thyro-hyoid. 



4. Internal laryngeal. } Crossing the space obliquely. 



5. External laryngeal. 



6. Spinal accessory. 

 7- " 



I! Sympathetic. } Bending vertically. 



Intercarotic body. 



Portion of the larynx and pharynx. 



Greater cornu of the hyoid bone. 



Lymphatic vessels and glands. 



This subdivision of the anterior triangle, when opened up, contains portions of each 

 of the three carotid arteries. It is well, however, that the dissector should clearly 

 understand that it is only after the parts are relaxed by dissection that these vessels 

 come to lie within the space. When the fascia and platysma are in position they 

 are completely overlapped by the sterno-mastoid muscle. The common carotid 



