larynx The larynx is the ‘voicebox’, the organ in the neck that plays a crucial role in
speech and
breathing. The channels for air and for food, which share the
pharynx at the back of the
nose and
mouth, diverge at this point, leading respectively to the trachea and to the
oesophagus. The opening for air through the larynx is known as the
glottis, and the
epiglottis, below and behind the
tongue, plays a necessary part in closing off the glottis during
swallowing.
The larynx has three important functions: control of the airflow during breathing, protection of the airway below it, and production of sound for
speech. The main part of the framework of the larynx is the
thyroid cartilage, and it is the front part of this that can easily be seen and felt as the ‘Adam's apple’. The larynx rests on the ring-shaped
cricoid cartilage, and below this is the trachea. Above, and attached by ligaments to the larynx at the front, is the U-shaped
hyoid bone that provides support and moves upwards with the larynx during swallowing. Halfway down the larynx the paired vocal folds (commonly known as the
vocal cords), formed by ligaments covered with mucous membrane, project inwards from its wall. The vocal folds form a ‘V’ shape, open towards the back. At the rear end of each vocal fold are the small
arytenoid cartilages. Many small muscles are attached to these, and their action can vary the size of the aperture, by pulling the arytenoids apart or drawing them nearer together, widening or narrowing the ‘V’. This movement occurs rhythmically during inhalation and exhalation in regular quiet breathing. Closure of the glottis occurs only momentarily during swallowing; abnormally, near-closure (
laryngospasm) seriously obstructs breathing and causes
stridor — high-pitched and noisy breathing.
During speech,
singing, or playing a wind instrument, the size of the aperture is narrowed and varied, to produce sounds of different pitch. This increased resistance to airflow out of the lungs converts the flow to a rapid pulsation as it passes between the vocal folds; this produces sound that is then modified by the upper vocal tract.
Marjorie P. Lorch
See
respiratory system.See also
breathing;
singing;
speech;
voice.