ORGANS OF VOICE AND RESPIRATION 207 



The left coronary artery arises from the left posterior sinus 

 of Valsalva. It passes behind and then to the left of the pul- 

 monary artery, and divides it into two branches, one of which 

 passes forwards and downwards in the anterior inter-ventri- 

 cular groove, and the other to the left and backwards along 

 the left auriculo-ventricular groove. 



The cardiac veins return the blood from the muscular 

 wall mainly through the coronary sinus into the right 

 auricle (p. 106). 



The nerves come from the cardiac plexuses. 



ORGANS OF VOICE AND RESPIRATION. 



THE LARYNX. 



The larynx lies in the front and upper part of the neck, 

 being placed below the tongue and hyoid bone and between 

 the large vessels of the neck. It opens above into the pharynx 

 and below into the trachea. It is subcutaneous in the middle 

 line, being covered only by skin and cervical fascia ; but 

 laterally it is overlaid by the insertions of the sterno-hyoid 

 and sterno-thyroid, by the thyro-hyoid and origin of the 

 inferior constrictor. Is composed of cartilages held together 

 by ligaments, and moved by muscles, the whole being lined 

 with mucous membrane. 



The cartilages of the larynx : 



The thyroid cartilage is the largest, consists of two wings 

 or alae united in front at an acute angle, and forming the 

 projection known as the pomum Adami. 



Outer surface : traversed by oblique line, passing upwards 

 and backwards, giving attachment to sterno-thyroid and 

 Ihyro-hyoid muscles, and below oblique line to inferior 

 constrictor. 



Inner surface : presents in the middle line at the junction of 

 right and left ala, the receding angle, to which are attached the 

 root of the epiglottis, the superior and inferior thyro-aryte- 

 noid ligaments, the thyro - arytenoidei and thyro-epiglottidei 

 muscles. 



Superior border ; sinuous ; connected to hyoid bone by 

 thyro-hyoid membrane ; the two meeting together anteriorly 

 in the mid-line form notch above pomum Adami. 



Inferior border : connected with upper border of cricoid by 

 crico- thyroid membrane anteriorly, and by crico-thyroid 

 muscle laterally. 



Posterior border : thick and rounded, receives insertion of 



