VOICE AND SPEECH. 865 



Cartilages of the Larynx. The mechanism of the larynx is supported 

 by a skeleton composed of several pieces of cartilage. The lowermost of these 

 cartilages is the cricoid cartilage, so called from its resemblance to a signet ring 

 (Fig. 296). The cricoid cartilage is situated above the topmost ring of the 

 trachea to which it is attached by a membrane. The vertical measurement of 

 the cricoid cartilage is about one inch on its posterior, and one-quarter inch on 

 its anterior surface. Superior to, and partly overlapping the cricoid, is the 

 thyroid cartilage, which forms an incomplete ring, being deficient posteriorly 

 (Fig. 296). The free corners of the thyroid behind are prolonged upward or 

 downward into projections known as the cornua. The upper pair are attached 

 to the extremities of the greater cornua of the hyoid bone, while by the inner 

 surface of the ends of the lower cornua the thyroid is articulated with the 

 cricoid cartilage and rotates upon it around an axis drawn through the points 

 of articulation. The lower anterior border of the thyroid cartilage is evenly 

 concave, but its upper border has a deep narrow notch in the middle line. 

 The upper half of the thyroid in front projects sharply forward in an elevation 

 known as Adam's apple (pomum Adami), which is much more marked in adult 

 males than in females. The elliptical space between the cricoid and thyroid 

 cartilages in front is covered by a membrane. Adam's apple, the anterior part 

 of the cricoid ring, and the space between the two, can easily be felt in the liv- 

 ing subject ; they rise perceptibly toward the head with each swallowing movement. 



The arytenoid cartilages are two in number and are similar in shape (Figs. 

 296, 297). Each cartilage, which has somewhat the form of a triangular 

 pyramid, is seated on, and articulates with, the highest point on the posterior 

 part of the cricoid cartilage some distance from the middle line. Of the free 

 faces of the pyramid, one looks backward, one toward the middle line, and the 

 third outward and forward. Each face is more or less concave. The apex of 

 each arytenoid cartilage is capped by a small body called the cartilage of San- 

 torini or, from its bent shape, corniculum laryngis (Figs. 296, 297). Outside 

 and in front of the latter is the minute cuneiform cartilage or cartilage of 

 Wrisberg, enclosed in the ary-epiglottic fold. The lateral posterior corner of 

 the arytenoid cartilage forms a blunt projection which serves for the attach- 

 ment of muscles, the processus muscularis. The anterior, lower, and median 

 part of each cartilage is of especial interest, since it serves for the posterior 

 attachment of the vocal cord ; it is known as the processus vocalis. 



The thyroid and cricoid cartilages and the body of the arytenoids are of 

 hyaline cartilage, and tend to become ossified in middle life. The other carti- 

 lages and the vocal processes of the arytenoids are composed of the elastic 

 variety. 



The Muscles of the Larynx may be divided into two classes the extrinsic 

 and the intrinsic ; the former find their origin outside the larynx, and the latter 

 both arise and are inserted within it. 



Extrinsic Muscles. To this group belong the sterno-hyoid, the sterno-thy- 

 roid, and the omo-hyoid muscles, which depress the larynx or hyoid bone ; the 

 thyro-hyoid muscle, which depresses the hyoid bone or elevates the thyroid 



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