The larynx, commonly known as the voice box, is a complex structure located in the middle of the neck. It sits just above the windpipe, or trachea, and connects the throat to the air passages of the lungs. This hollow, tube-shaped organ measures approximately 4 to 5 centimeters in both length and width in adults and is primarily composed of cartilage, muscles, and elastic tissues.
This structure is a fundamental component of the respiratory system. Its precise positioning and intricate design allow it to perform several functions. The larynx is involved in processes ranging from communication to ensuring the safety of the respiratory tract.
Voice Production
The larynx plays a primary role in creating sound for speech and singing. Within its structure are two bands of muscle and tissue known as vocal cords, or vocal folds. These vocal folds stretch horizontally across the larynx, from front to back.
Sound is produced when air from the lungs passes through the vocal folds, causing them to vibrate rapidly. This wave-like motion is driven by aerodynamic forces. Air pressure builds below the folds, pushing them apart, and as air escapes, a low-pressure area (Bernoulli effect) pulls them back together, completing a cycle.
The pitch of the sound produced is determined by the speed of these vibrations, influenced by the length and tension of the vocal folds. Shorter, thicker, and less taut vocal folds vibrate more slowly, resulting in a lower pitch. Longer, thinner, and more taut vocal folds vibrate faster, creating a higher pitch. The volume of the sound depends on the force of the air passing through and the amplitude of the vocal fold vibration.
Once the basic sound is generated by the vocal folds, it travels upwards through the throat, mouth, and nasal passages. These surrounding structures, including the pharynx, tongue, and lips, act as resonators and articulators. They modify and shape the raw sound, transforming it into recognizable speech and a wide range of vocalizations.
Airway Protection
Another important function of the larynx is to protect the airway from foreign substances, such as food and liquids, during swallowing. The larynx is located at a junction where the digestive and respiratory pathways meet. This position necessitates a protective mechanism to prevent ingested materials from entering the lungs.
When swallowing occurs, a coordinated series of movements takes place. The larynx moves upwards and slightly forwards. Simultaneously, a leaf-shaped flap of cartilage called the epiglottis, positioned at the top of the larynx, folds backward to cover the entrance to the windpipe.
This action effectively diverts food and liquids away from the trachea and into the esophagus. In addition to the epiglottis, the vocal cords tightly close during swallowing, forming an extra seal. This layered protection ensures food and drink are directed down the correct pathway, minimizing the risk of choking or aspiration.
Airflow Regulation
The larynx also regulates the flow of air into and out of the lungs during breathing. The vocal folds, which create sound, also control the opening and closing of the airway. This opening, known as the glottis, expands or narrows to manage the amount of air passing through.
During quiet breathing, the vocal folds are relaxed and remain open, allowing air to move freely to and from the lungs. When more air is needed, such as during physical exertion, the vocal folds can widen further to maximize airflow. Conversely, they can narrow slightly to control the rate of air expelled during exhalation.
This regulatory ability is also evident in protective reflexes like coughing and sneezing. In these instances, the vocal folds tightly close, building up air pressure below them. When they suddenly open, the forceful expulsion of air helps to clear irritants or obstructions from the airway.