THE ORGANS OF VOICE AND RESPIRATION. 



THE LARYNX. 



Larynx is the organ of voice, placed at the upper part of the air-passage. 

 A It is situated between the trachea and base of the tongue, at the upper and 

 fore part of the neck, where it forms a considerable projection in the middle line. 

 On either side of it lie the great vessels of the neck ; behind, it forms part of the 

 boundary of the pharynx, and is covered by the mucous membrane lining that 

 cavity. Its vertical extent corresponds to the fourth, fifth, and sixth cervical 

 vertebrae, but it is placed somewhat higher in the female and also during childhood. 

 In infants between six and twelve months of age Symington found that the tip of 

 the epiglottis was a little above the level of the cartilage, between the odontoid 

 process and body of the axis, and that between infancy and adult life the larynx 

 descends for a distance equal to two vertebral bodies and two intervertebral disks. 

 According to Sappey, the average measurements of the adult larynx are as follows : 



In males. In females. 



Vertical diameter . . . .44 mm. 36 mm. 



Transverse diameter .... 43 u 41 " 



Antero-posterior diameter ... 36 u 26 " 



Circumference ..... 136 " 112 " 



Until puberty there is no marked difference between the larynx of the male 

 and that of the female. In the latter its further increase in size is only slight, 

 whereas in the former it is great; all the cartilages are enlarged, and the thyroid 

 becomes prominent as the pomum Adami in the middle line of the neck, while 

 the length of the glottis is nearly doubled. 



The larynx is broad above, where it presents the form of a triangular box, 

 flattened behind and at the sides, and bounded in front by a prominent vertical 

 ridge. Below, it is narrow and cylindrical. It is composed of cartilages, which 

 are connected together by ligaments and moved by numerous muscles. It is lined 

 by mucous membrane, which is continuous above with that lining the pharynx and 

 below with that of the trachea. 



The Cartilages of the Larynx are nine in number, three single, and three 

 pairs : 



Thyroid. Two Arytenoid. 



Cricoid. Two Cornicula Laryngis. 



Epiglottis. Two Cuneiform. 



The thyroid (dopeo^, a shield) is the largest cartilage of the larynx. It con- 

 sists of two lateral lamellae or alae, united at an acute angle in front, forming a 

 vertical projection in the middle line which is prominent above, and called the 

 pomum Adami. This projection is subcutaneous, more distinct in the male 

 than in the female, and occasionally separated from the integument by a bursa 

 mucosa. 



Each lamella is quadrilateral in form. Its outer surface presents an oblique 

 ridge, which passes downward and forward from a tubercle, situated near the root 

 of the superior cornu, to a small tubercle near the anterior part of the lower 

 border. This ridge gives attachment to the Sterno-thyroid and Thyro-hyoid 



