The Larynx (fig. 198) is a chamber of irregular form externally, which is connected with the hyoid bone or bone of the tongue (a, b, c) above and in front by means of a small ligament, and is continuous with the trachea behind. The chief of the cartilages composing it is named the thyroid (h), from its resemblance to a shield. It consists of two winglike portions, joined at an angle in front, but open behind. To its fore part is attached the epiglottis (e) (fig. 199), a tongue-shaped body which covers the entrance to the glottis when food is swallowed, thus preventing the passage of any portion of it into the larynx or trachea.
Behind the thyroid cartilage is the cricoid cartilage (g), which resembles a signet-ring with the wider part above (fig. 198). Articulating with this wider part behind are the two arytsenoid cartilages (fig. 198). These are of pyramidal form, and the vocal cords or organs of voice extend from their inferior angle to the internal surface of the thyroid cartilage.
The larynx possesses many muscles which effect the movements of the several cartilages on one another during respiration, and by tightening the vocal cords determine the pitch of the notes which the animal is capable of emitting.