Ill 



PHONATION AND AKTICULATION 



135 



Here the mucous membrane forms on each side two thick trans- 

 verse ridges which extend from the base of the epiglottis backwards 

 to the vocal processes of the arytenoids. The two upper ridges are 

 known as the false, and the two lower as the true vocal cords. The 

 former project less towards the median line of the glottis than the 

 latter. Between the true and false vocal cords are two recesses, 

 known as the ventricle of Morgagni (Fig. 94). 



The elastic fibres of the submucosa are highly developed in the 



FIG. 90. Laryngeal cartilage with fascia, ligaments, and insertions of certain muscles. (Henle.) 

 Oh, hyoid bone ; e, epiglottis ; Cs, superior horn of thyroid cartilage ; he, hyo-epiglottic 

 ligament ; htl, lateral hyo-thyroid ligament ; tr, cartilage tritica ; te, thyro-epiglottic cartilage ; 

 ca, crico - ary tenoid cartilage: tas, tai, superior and inferior thyro - ary tenoid ligaments; 

 Caff, Cap", insertions of posterior crieo-arytenoid muscle ; Lp, insertion of laryngo-pharyngeal 

 muscle. 



true vocal cords, and form compact bands which run through their 

 whole length ; they are wedge-shaped in cross-section, and covered 

 by a layer of non-ciliated pavement epithelium. In the false vocal 

 cords the elastic connective tissue is much less abundant, and the 

 mucous membrane that covers it is rich in adenoid tissue, which is 

 even more plentiful in the laryngeal ventricles and on the posterior- 

 inferior surface of the epiglottis. The mucous membrane of these 

 parts soon becomes oedematous from accumulation of lymph in the 

 lymph-spaces, which may obstruct respiration and cause suffocation 

 by closure of the glottis. 



Owing to their elasticity the true vocal cords extend and con- 

 tract without falling into folds, and their delicate free edges, 



