Organs of Yoice and Respiration. 



THE LARYNX. 



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

 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. 



The larynx is narrow and cylindrical below, but broad above, where it pre- 

 sents the form of a triangular box, flattened behind and at the sides, whilst in 

 front it is bounded by a prominent vertical ridge. It is composed of carti- 

 lages, which are connected together by ligaments and moved by numerous mus- 

 cles ; the interior is lined by mucous membrane, and supplied with vessels and 

 nerves. 



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

 pairs : 



Thyroid. 



Cricoid. 



Epiglottis. 



Two Arytenoid. 



Two Cornicula Laryngis. 



Two Cuneiform. 



Fig. 422. Side View of the Thyroid 

 and Cricoid Cartilages. 



The Thyroid (0vpso?, a shield) is the largest cartilage of the larynx. It consists 

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

 projection in the middle line, which is promi- 

 nent above, and called the pomum Adami. This 

 projection is subcutaneous, more distinct in the 

 male than in the female, and occasionally sepa- 

 rated from the integument by a bursa mucosa. 



Each lamella is quadrilateral in form. Its 

 outer surface presents an oblique ridge, which 

 passes downwards and forwards from a tubercle, 

 situated near the root of the superior cornu. 

 This ridge gives attachment to the Sterno-thy- 

 roid and Thyro-hyoid muscles ; the portion of 

 cartilage included between it and the posterior 

 border, to part of the Inferior Constrictor 

 muscle. 



The inner surface of each ala is smooth, con- 

 cave, and covered by mucous membrane above 

 and behind ; but in front, in the receding angle 

 formed by their junction, is attached the epiglot- 

 tis, the true and false chordas vocales, the Thyro- 

 arytenoid, and Thyro-epiglottidean muscles. 



The upper border of the thyroid cartilage is 

 deeply notched in the middle line immediately 

 above the pomum Adami, whilst on either side 

 it is slightly concave. This border gives attach- 

 ment throughout its whole extent to the thyro- 

 hyoid membrane. 



The lower border is connected to the cricoid cartilage, in the median line, by 

 the crico-thyroid membrane ; and, on each side, by the Crico-thyroid muscle. 

 49 769 



