The pharynx connects the nasal and oral cavities to the larynx and esophagus. It serves as a passageway for air and food and acts as a resonating chamber for speech. The pharynx is located posterior to the nasal and oral cavities and is divided regionally into the nasopharynx and oropharynx, respectively (see Fig. 19.2). The auditory (Eustachian) tubes connect the nasopharynx to each middle ear. Diffuse lymphatic tissue and lymphatic nodules are present in the wall of the nasopharynx. The concentration of lymphatic nodules at the junction between the superior and posterior walls of the pharynx is called the pharyngeal tonsil.
The passageway for air between the oropharynx and trachea is the larynx (see Fig. 19.2). This complex tubular region of the respiratory system is formed by irregularly shaped plates of hyaline and elastic cartilage (the epiglottis and the vocal processes of the arytenoid cartilages). In addition to serving as a conduit for air, the larynx serves as the organ for producing sounds.
Vocal folds control the flow of air through the larynx and vibrate to produce sound.
The vocal folds, also referred to as vocal cords, are two folds of mucosa that project into the lumen of the larynx (Fig. 19.5 and Plate 70, page 690). They are oriented in an anteroposterior direction and define the lateral boundaries of the opening of the larynx, the rima glottidis. A supporting ligament and skeletal muscle, the vocalis muscle, is contained within each vocal fold. Ligaments and the intrinsic laryngeal muscles join the adjacent cartilaginous plates and are responsible for generating tension in the vocal folds and for opening and closing the glottis. The extrinsic laryngeal muscles insert on cartilages of the larynx but originate in extralaryngeal structures. These muscles move the larynx during deglutition (swallowing).
Expelled air from lungs passing through a narrow space of rima glottidis causes the vocal folds to vibrate. The vibrations are altered by modulating the tension on the vocal folds and by changing the degree of glottal opening. This alteration of the vibrations produces sounds of different pitch. Sounds created in the larynx during the process of phonation are modified in upper parts of the respiratory system (nasopharynx, nasal cavities, and paranasal sinuses) and the oral cavity (oropharynx, soft and hard palate, tongue, teeth, lips, etc.) to produce the individual speech sounds (different vowels and consonants).
The ventricular folds located above the vocal folds are the “false vocal cords.”
Above the vocal folds is an elongated recess in the larynx called the ventricle. Immediately above the ventricle is another pair of mucosal folds, the ventricular folds, or false vocal cords (see Fig. 19.5 and Plate 70, page 690). These folds do not have the intrinsic muscular investment of the true vocal cords and therefore, do not modulate in phonation. They and the ventricle, however, are important in creating sound resonance. Inﬂammation and swelling of the larynx caused by viruses (such as in common cold virus) and other microbial agents is called acute laryngitis. Symptoms of acute laryngitis may include hoarseness or, in more severe cases, the total loss of voice, coughing, and difficulty with swallowing and breathing. Chronic laryngitis is usually caused by prolonged exposure of irritating agents such as tobacco smoke, dust, and/or polluted air.
Stratified squamous and ciliated pseudostratified columnar epithelium line the larynx.