1078 SPLANCHNOLOGY 



tricular and vocal ligaments, the upper portion extends between the arytenoid 

 cartilage and the epiglottis and is often poorly defined; the lower part is a well- 

 marked membrane forming, with its fellow of the opposite side, the conus elasticus 

 which connects the thyroid, cricoid, and arytenoid cartilages to one another. 

 In addition the joints between the individual cartilages are provided with ligaments. 



The Conus Elasticus (cricothyroid membrane) is composed mainly of yellow elastic 

 tissue. It consists of an anterior and tw T o lateral portions. The anterior part or 

 middle cricothyroid ligament (ligamentum cricothyreoideum medium; central part of 

 cricothyroid membrane) is thick and strong, narrow above and broad below. It 

 connects together the front parts of the contiguous margins of the thyroid and 

 cricoid cartilages. It is overlapped on either side by the Cricothyreoideus, but 

 between these is subcutaneous; it is crossed horizontally by a small anastomotic 

 arterial arch, formed by the junction of the two cricothyroid arteries, branches 

 of which pierce it. The lateral portions are thinner and lie close under the mucous 

 membrane of the larynx; they extend from the superior border of the cricoid cartil- 

 age to the inferior margin of the vocal ligaments, with which they are continuous. 

 These ligaments may therefore be regarded as the free borders of the lateral por- 

 tions of the conus elasticus, and extend from the vocal processes of the arytenoid 

 cartilages to the angle of the thyroid cartilage about midway between its upper 

 and lower borders. 



An articular capsule, strengthened posteriorly by a well-marked fibrous band, 

 encloses the articulation of the inferior cornu of the thyroid with the cricoid car- 

 tilage on either side. 



Each arytenoid cartilage is connected to the cricoid by a capsule and a posterior 

 cricoarytenoid ligament. The capsule (capsula articularis cricoarytenoidea) is thin 

 and loose, and is attached to the margins of the articular surfaces. The posterior 

 cricoarytenoid ligament (ligamentum cricoarytenoideum posterius) extends from the 

 cricoid to the medial and back part of the base of the arytenoid. 



The thyroepiglottic ligament (ligamentum thyreoepiglotticum) is a long, slender, 

 elastic cord which connects the stem of the epiglottis with the angle of the thyroid 

 cartilage, immediately beneath the superior thyroid notch, above the attachment 

 of the ventricular ligaments. 



Movements. The articulation between the inferior cornu of the thyroid cartilage and the 

 cricoid cartilage on either side is a diarthrodial one, and permits of rotatory and gliding move- 

 ments. The rotatory movement is one in which the cricoid cartilage rotates upon the inferior 

 cornua of the thyroid cartilage around an axis passing transversely through both joints. 

 The gliding movement consists in a limited shifting of the cricoid on the thyroid in different 

 directions. 



The articulation between the arytenoid cartilages and the cricoid is also a diarthrodial one, 

 and permits of two varieties of movement : one is a rotation of the arytenoid on a vertical axis, 

 whereby the vocal process is moved lateralward or medialward, and the rima glottidis increased 

 or diminished; the other is a gliding movement, and allows the arytenoid cartilages to approach 

 or recede from each other; from the direction and slope of the articular surfaces lateral gliding 

 is accompanied by a forward and downward movement. The two movements of gliding and 

 rotation are associated, the medial gliding being connected with medialward rotation, and the 

 lateral gliding with lateralward rotation. The posterior cricoarytenoid ligaments limit the 

 forward movement of the arytenoid cartilages on the cricoid. 



Interior of the Larynx (Figs. 953, 954). The cavity of the larynx (cavum 

 laryngis) extends from the laryngeal entrance to the lower border of the cricoid 

 cartilage where it is continuous with that of the trachea. It is divided into two 

 parts by the projection of the vocal folds, between which is a narrow triangular 

 fissure or chink, the rima glottidis. The portion of the cavity of the larynx above 

 the vocal folds is called the vestibule ; it is wide and triangular in shape, its base 

 or anterior wall presenting, however, about its center the backward projection 

 of the tubercle of the epiglottis. It contains the ventricular folds, and between 

 these and the vocal folds are the ventricles of the larynx. The portion below the 



