THE MOUTH AND THROAT. 125 



The thyrohyoid membrane passes between the hyoid bone above and the 

 thyroid cartilage below ; crossing it is the hyoid branch of the superior thyroid artery. 

 It is a quite small vessel, of little clinical importance, and ordinarily does not reach 

 the median line. 



The posterior edge of this membrane, running from the superior corner of the 

 thyroid cartilage to the hyoid bone, is called the thyrohyoid ligament. This liga- 

 ment has a small cartilaginous nodule in it, the cartilago triticea. Piercing the 

 membrane on its side are the internal branches of the superior laryngeal nerve 

 and the superior laryngeal vessels. The external branch of the superior laryngeal 

 nerve supplies the cricothyroid muscle, while the internal is the nerve of sensation 

 of the larynx. 



Pharyngotomy. Sometimes, in order to remove foreign bodies in the larynx or 

 oesophagus, an opening is made through the membrane between the hyoid bone and 

 thyroid cartilage. 



Thyroid Cartilage. This is the largest cartilage of the larynx and contains 

 the vocal cords. They lie immediately behind or just below the most prominent 



Greater cornu 



Body of hyoid bone ^ j i njj^BP^^W 1 TniHn triticea 



Thyrohyoid membrane- 

 Superior cornu 



Thyroid cartilage 



fur | 



^^^ , -^_^^^ -Inferior cornu 



Cricothyroid membrane - 



Cricoid cartilage 



FIG. 158. Side view of hyoid bone and larynx. 



portion of its anterior edge, commonly called "Adam's apple." Since the cartilage 

 is large and strong and as age advances tends to calcify, cut-throat wounds, while 

 opening the cavity within, do not often pass entirely through the cartilage. This 

 cartilage may be fractured by violence. This is often fatal on account of the blood 

 flowing into the trachea and lungs below or on account of oedema of the lining mucous 

 membrane causing obstruction of the breathing. Thyrotomy or division of the 

 thyroid cartilage in the median line is sometimes done to remove foreign bodies or 

 new growths. In these cases the voice will be likely to be impaired by the interference 

 with the vocal cords. 



Cricothyroid Membrane. The space between the cricoid and thyroid carti- 

 lages is small. This is due to the increase in width of the cricoid as it proceeds back- 

 ward. The space is readily felt on the living subject between the thyroid above and 

 the cricoid beneath ; the membrane passes between them. It is crossed by a small 

 branch of the superior thyroid artery, the cricothyroid. It is not large enough to cause 

 serious trouble. Introducing a tube through this membrane constitutes the operation 



