The pharynx, or throat, is a continuation backward and downward of the nasal and oral cavities. It serves as a food and air passageway. At the upper portion behind the soft palate lies the adenoid. At the sides of the back of the tongue on either side is the tonsil. The tonsils and adenoids are similar in structure—lobulated irregular masses attached on one surface to their beds. The tonsils may be seen through the open mouth while the adenoid is hidden from view except by use of instruments.
Surrounding the throat are sets of muscles which contract rhythmically in co-ordination with the base of the tongue for the process of swallowing. Masticated boluses of food and liquid are forced backward and downward into the esophagus (gullet). As this process takes place, the epiglottis is forced down over the air opening of the air passage of the larynx; and the soft palate is pushed up against the back of the throat. By these actions the air passages are covered to prevent food from entering.
The “voice box,” or larynx, is the enlarged air passage at the top of the windpipe (trachea), composed of cartilage. This protrudes somewhat in the front of the neck as the “Adam’s apple.” It is surrounded by muscles which elevate it against the epiglottis during swallowing. Within the upper part of this irregularly funnel-shaped organ are the vocal cords. These are a pair of elastic bands extending from front to back on either side. The opening between them is the glottis. Air forced through this area causes the cords to vibrate during speech. By delicate muscle fibers the cords are placed under varying degrees of tension, so that the pitch of the voice is made to vary. The shape of the air cavity of the larynx modifies voice phonation.
The air passage to the lung extends downward from the base of the larynx as the trachea. This is a tube 4 to 5 inches long which divides at its lower end into the right and the left bronchus. The trachea is composed of rings of cartilage, 15 to 20 in number, held together by elastic tissue; these give firmness to the structure and prevent collapse. It is lined with a protective membrane.