Organs of Voice and Eespiration. 



355. Side View of the Thyroid 

 aud Cricoid Cartilages. 



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 this 

 cavity. 



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

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

 front it is bounded by a prominent vertical ridge. It is composed of cartilages, 

 connected together by ligaments, moved by numerous muscles, 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. Two Arytenoid. 



Cricoid. Two Cornicula Laryngis. 



Epiglottis. Two Cuneiform. 



The Tliyroid (Ovpeo? tlSos, like a shield) is the largest cartilage of the larynx. 

 It consists of two lateral lamellae or alas, 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 subcu- 

 taneous, 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 downwards and for- . 

 wards from a tubercle, situated near the 

 root of the superior cornu. This ridge 

 gives attachment to the Ster no -thyroid 

 and Thyro-hyoid muscles; the portion of 

 cartilage included between it and the poste- 

 rior border, to part of the Inferior constric- 

 tor muscle. 



The inner surface of each ala is smooth, 

 concave, and covered by mucous membrane 

 above and behind ; but in front, in the re- 

 ceding angle formed by their junction, are 

 attached the epiglottis, the true and false 

 chordaB vocales, the Thyro-arytenoid and 

 Thyro-epiglottidean muscles. 



The upper border of the thyroid carti- 

 lage is deeply notched in the middle line, 

 immediately above the pomum Adami, 

 whilst on either side it is slightly concave. 

 This border gives attachment throughout its whole extent to the thyro-hyoid 

 membrane. 



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

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



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