1072 THE KESPIKATOEY SYSTEM. 



producing what is known as oedema glottidis. This may proceed so far as to cause occlusion of 

 the upper part of the cavity. The close adhesion of the mucous membrane to the vocal folds, 

 however, prevents the oedema -extending beyond the level of the rima glottidis, and the surgeon 

 is thus able to relieve the patient by making an opening through the ventral part of the conns 

 elasticus into the cavity of the larynx. 



Above the level of the rima glottidis the laryngeal mucous membrane is 

 extremely sensitive, and when touched by a foreign body there is an immediate 

 response in the shape of an explosive cough. In the lower compartment of the 

 larynx the mucous membrane is lined with columnar ciliated epithelium. Over 

 the vocal folds this is replaced by squamous epithelium. In the ventricle of the 

 larynx and in the inferior part of the vestibule of the larynx the columnar ciliated 

 epithelium again reappears. The upper part of the epiglottis and the upper parts 

 of the lateral walls of the vestibule are covered with squamous epithelium similar 

 to that present in the mouth and pharynx. 



The mucous membrane of the larynx has a plentiful supply of acinous glands, 

 and in only one place, viz., over the surface of the vocal folds, are these com- 

 pletely absent. For the most part the glands are aggregated in groups. The 

 following are the localities in which these groups are especially noticeable : (1) On 

 the dorsal surface of the epiglottis, many of the glands piercing the cartilage ; (2) 

 around the cuneiform cartilage, where they are chiefly responsible for the elongated 

 elevation seen in this part of the wall of the vestibule ; (3) in the ventricular folds 

 and over the wall of the laryngeal vestibule and the appendix ventriculi laryngis. 



MUSCULI LARYNGIS. 



Of the several muscles attached to the cartilages of the larynx all do not 

 physiologically belong to the larynx, as, for example, the inferior constrictor 

 muscles of the pharynx, which, though attached to both cricoid and thyreoid 

 cartilages, belong to the muscles of the pharynx, as do also the stylo-pharyngeus 

 and palato-pharyngeus muscles inserted in part into the thyreoid cartilage. 



The true physiological muscles of the larynx may be divided into two great 

 groups, extrinsic and intrinsic. The extrinsic laryngeal muscles comprise all! 

 muscles passing to the os hyoideum, which is physiologically a part of the 

 laryngeal apparatus, as well as the m. sterno-thyreoideus. They have already been 

 described in the section on muscles. 



The intrinsic laryngeal muscles are nineteen in number, nine paired and one| 

 unpaired. They may be roughly classified physiologically as follows : 



A. Constrictor muscles of the larynx, including the adductors of the vocal folds 

 Mm. cricoarytsenoidei laterales. Paired. 



Mm. thyreoarytsenoidei. Paired. 

 M. arytaenoideus transversus. Unpaired. 

 Mm. arytsenoidei obliqui. Paired. 

 Mm. aryepiglottici. Paired. 



B. Dilator muscles of the larynx, including the abductors of the vocal folds 

 Mm. cricoarytsenoidei posteriores. Paired. 



Mm. thyreoepiglottici. Paired. 



C. Muscles modifying the tension of the vocal cords 

 Mm. cricothyreoidei. Paired. 



Mm. vocales. Paired. 



Mm. ventriculares. Paired. 



Mm. thyreoarytaenoidei (also constrictors). Paired. 



The mm. cricoarytsenoidei laterales are a pair of triangular muscles, 

 of which lies in the lateral wall of the larynx upon the conus elasticus and coi 

 cealed by the lamina of the thyreoid cartilage, the thyreoid gland, and the inf 

 hyoid muscles. 



Each muscle arises from the upper border and the lateral surface of the 

 of the cricoid cartilage as far dorsally as the facet which supports the base of tl 

 arytrenoid cartilage, and also from the lateral part of the conus elasticus. 



