MEMBRANES OF THE LARYNX 1215 



of the cricoid, is important in helping to fix the former cartilage in place upon the sloping 

 aryteenoid articular surface of the cricoid and in limiting its movements. Motion at this 

 articulation is very free. The following simple movements of the arytaenoid are best under- 

 stood: — (1) ghding of the arytaenoid toward or away from its fellow; (2) inclining forward and 

 backward; (3) rotating on a vertical axis, so that the vocal process sweeps medialward or lateral- 

 ward and also a little downward or upward. 



The union of the corniculate cartilage with the apex of the arytaenoid cartilage 

 [synchondrosis arycorniculata] is usually by connective tissue; rarely is there a 

 joint cavity. 



The petiole of the epiglottic cartilage is connected with the thyreoid, below 

 and behind the superior notch, by a strong, elastic thyreo-epiglottic ligament 

 [lig. thyreoepiglotticum] (fig. 977). 



(2) The Elastic Membrane of the Larynx 

 [Membrana elastica laryngis] 



This name is given to a more or less continuous sheet of elastic fibres connected 

 with the deeper parts of the laryngeal mucosa. Its upper part is known as the 

 quadrangular membrane, the lower part as the elastic cone. A middle region of the 

 elastic membrane lies opposite the ventricle of the larynx. 



The quadrangular membrane (figs. 978, 981, 988) extends from the ary-epi- 

 glottic folds above to the level of the ventricular folds (false vocal cords) below. 

 The lateral parts of this membrane are widely separated superiorly, but they con- 

 verge toward the middle fine as they descend. Anteriorly, the membrane is 

 fixed in the angle of the thyreoid laminae and to the sides of the epiglottic car- 

 tilage; posteriorly, to the corniculate cartilages and to the arytaenoids. The 

 superior edge on either side lies within the ary-epiglottic fold, which it supports; 

 it slopes downward and backward and includes the cuneiform cartilage. The 

 inferior edge, horizontal and in a sagittal plane, is best developed in front, where 

 it is attached in the angle of the thyreoid a little way from the middle line ; behind, 

 it is fixed to the medial margin of the triangular fovea of the arytaenoid. This 

 inferior free margin, differentiated as the ventricular ligament [lig. ventriculare], 

 is enclosed within, and is the support for the ventricular fold. 



Fig. 979. — The Elastic Cone seex from Above. (Modified from Luschka.) 



Nodule of elastic tissue ^,,_^__Perichondral insertion of vocal ligaments 



-^Nodule of elastic tissue 

 ^Vocal ligament 

 Elastic cone 

 ^ .Cricoid cartilage 



section 



_ ., ., - ^ as^j I SB w^^B-fe ■ H KB a Thyreoid cartilage in transverse 



Thyreoid cartilage m transverse_tf'y(' I >» J?^^Bv^ " |fll Mm \ — section 



Arytaenoid cartilage in transverse section 

 Posterior crico-arytsenoid ligament 



The elastic cone [conus elasticus] (figs. 978, 979). — This part of the elastic 

 membrane extends from the level of the vocal folds to the superior margin of the 

 cricoid cartilage. Its component fibres are attached in the re-entrant angle and 

 adjacent lower margin of the thyreoid cartilage, whence the}^ spread downward 

 and backward to the upper edge of the cricoid arch and to the arytaenoid carti- 

 lages. The strong anterior portion, perforated by vessels, is the median crico- 

 thyreoid ligament [Kg. cricothyreoideum (medium)] (figs. 974, 975). The lateral 

 parts (lateral portions of the crico-thyreoid membrane) present superior free 

 edges, somewhat thickened, which, running horizontally near the middle line from 

 the thyreoid angle to the vocal processes, constitute the vocal ligaments. These 

 are inserted anteriorly into a perichondral process in the thyreoid angle; poster- 

 iorly, they have a wide area of attachment to the upper and medial surfaces of the 

 vocal processes of the arytaenoids with the elastic fibres of which they are in part 

 continuous. A yellowish, cellular nodule (sometimes cartilage) occurs in the 



