Page:Structure and functions of the body; a hand-book of anatomy and physiology for nurses and others desiring a practical knowledge of the subject (IA structurefunctio00fiskrich).pdf/128

 the cavity of the larynx. Inside and resting on the upper border of the cricoid are the two smaller arytenoid or pitcher-like cartilages, pyramidal in shape, and surmounting these again the two cornicula laryngis. The two cuneiform cartilages are in the free borders of the folds of mucous membrane which extend from the apex of the arytenoids to the sides of the epiglottis. Numerous small muscles serve to bind these various cartilages together.

At the angle of the thyroid cartilage in front are attached the epiglottis at the top and just below that the superior or false vocal cords, two folds of mucous membrane enclosing the superior thyro-arytenoid ligaments. Lower still are found the inferior or true vocal cords, which are formed by the inferior thyro-arytenoid ligaments covered with a thin, tightly fitting mucous membrane. Both sets of vocal cords as well as the epiglottis may be seen by means of a head and a throat mirror. Between the true vocal cords is a narrow triangular interval called the glottis. It is by means of the vibrations of these cords that sound is produced. The false vocal cords cannot produce sound, though they can modify it indirectly. Quality of voice, as treble, base, etc., depends upon the size of the larynx and the length and elasticity of the vocal cords. Modulation is produced by changing the form of the cavity of the mouth and nose. In whispering the lips take the place of the vocal cords and produce sound by the vibration of their muscular walls.

Instead of tracheotomy laryngotomy is sometimes done in the depression between the thyroid and the cricoid, which may be felt on the living. Foreign bodies sometimes get into the larynx and have to be removed, or the mucous membrane may become inflamed, causing laryngitis. Syphilis attacks the larynx, and tuberculosis and cancer of the larynx occur, these last two being generally fatal. Edema of the glottis may also occur.