694 



DISSECTION OF THE LARYNX. 



andbmuUl). 



Form during 

 life; 



in easy 

 respiration ; 



in forced 

 inspiration ; 



in produc- 

 tion of the 



Muscles 

 producing 

 changes in 

 glottis. 



Ventricle : 

 situation. 



Pouch of 

 larynx : 



form and 

 position ; 



surrounding 

 parts. 



Dissection 

 of vocal 



cords, 



interval measures nearly an inch from before backwards ; in tin- 

 /'' male, nearly a quarter of an inch less. Its breadth at the base, 

 is about one-third of the length. The length of the glottis is 

 increased by the stretching, and shortened by the relaxation of the 

 vocal cords. 



In quiet breathing the glottis has the triangular form seen after 

 death, the space being slightly widened in inspiration, and narrowed 

 in expiration. In forcible inspiration it becomes widely dilated, 

 the vocal processes of the arytenoid cartilages being directed out- 

 wards, and the aperture acquiring the form of a lozenge with the 

 posterior angle truncated. The widest part is then opposite the 

 junction of the vocal cords with the arytenoid cartilages, and its 

 transverse measurement is about one half of the length. During 

 vocalisation the cords and the A T ocal processes of the arytenoid 

 cartilages are brought together, and the vocal glottis is reduced to a 

 narrow chink, while the hinder part of the space is closed by the 

 meeting of the anterior borders of the arytenoid cartilages. 



The glottis is rendered longer, and the vocal cords are tightened 

 by the crico-thyroid muscles ; the opposite effect is produced by the 

 elasticity of the cords and the contraction of the thyro-arytenoid 

 muscles. Widening of the glottis is effected by the posterior crico- 

 arytenoid muscles ; and the cords and arytenoid cartilages are 

 approximated by the thyro-arytenoid, lateral crico-arytenoid, and 

 arytenoid muscles. 



The ventricle of the larynx (fig. 247, A) is best seen on the left 

 side. It is the boat-shaped hollow between the vocal cords, the 

 upper margin being concave, and the lower nearly straight. It is 

 lined by the mucous membrane, and on the outer surface are the 

 fibres of the thyro-arytenoid muscle. In its roof, towards the front, 

 is the aperture of the laryngeal pouch. 



The laryngeal pouch or sacculus laryngis (fig. 247, D), has been 

 laid bare partly on the right side by the removal of the ala of the 

 thyroid cartilage, but it will be opened in the subsequent dissection 

 for the vocal cords. 



It is a small membranous sac, about half an inch long and rather 

 conical in form, which projects upwards between the false vocal 

 cord and the ala of the thyroid cartilage, reaching as high as the 

 upper border of the latter. Its cavity communicates with the fore 

 part of the ventricle by a somewhat narrow aperture. On the deep 

 surface of the mucous lining are numerous small glands, the ducts 

 of which open on the inside. Its outer side is covered by the 

 thyro-epiglottidean muscle. The size and extent of the pouch vary 

 greatly in different subjects. 



Dissection. The general shape and position of the vocal cords 

 are evident on the left half of the larynx, but to show more fully the 

 nature of the lower cord, put the cut surfaces in contact, and detach 

 on the right side the lateral crico-arytenoid muscle from its cartilages. 

 Take away in like manner the thyro-arytenoid, raising it from before 

 back. By the removal of the last muscle an elastic membrane, crico- 



