Larynx or Voice Box - Structure, Functions, Disorders
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Larynx or Voice Box : The Base for Speech

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 14 Feb 2014 - 14:23.

Gifted are those who have voice. More gifted are those with good voice. Exceptionally gifted are those with melodious voice. The human Larynx also called the 'Voice Box' governs all these categories.

The Larynx is an organ situated in the neck and plays a vital role in the functioning of breathing as well as production of speech. It is positioned at a point where the air-digestive tract splits into two separate pathways; one allowing inhaled air to pass through a tube called trachea or windpipe in to the lungs, and the other from where  the food ingested passes through a pipe like structure called esophagus and thence to the stomach. Because of its strategic location, the larynx plays three important roles, namely:

  • Control of airflow during the act of breathing
     
  • Protection of the airways and
     
  • Production of sound in the form of speech or voice.

Larynx structure: The larynx is made up of a cartilage with a soft tissue around it. The thyroid cartilage occupies the most prominent portion of the larynx which is visible as a protrusion in the neck, especially those who have a lean personality is called as the ‘Adam’s Apple’. A u-shaped bone called ‘hyoid’ is situated right on top of the larynx. The hyoid bone which itself is attached to the mandible with muscles and tendons supports the larynx from above. These attachments help in elevating the larynx during the acts of swallowing and speaking. Down below at its lower end, the larynx is in the form of a cartilage called the ‘cricoid’ which is like a signet ring most of which is at the back. Immediately below the cricoid lie the rings of the trachea.

Functions of the Larynx: The vocal folds or vocal cords are situated in the center of the larynx. The vocal cords are the most important parts of the larynx since they play a vital role in its three principal functions. The vocal cords are made of muscles and covered by a mucous membrane. There is a right and left vocal cord one on each side, which appears like the letter 'V' when looked from above.

Behind each vocal cord is a cartilaginous portion called arytenoids to which are attached small muscles. When these muscles contract, they pull the arytenoids apart from each other while breathing to open the airways. During speech the arytenoids and vocal cords are brought closer together. They open and close rapidly and as air passes through them a sound is produced, which the remainder of the vocal tract modifies to produce speech. The same mechanism is involved in the act of singing or delivering a powerful speech or even a whisper according to which the vocal cords modify themselves.

The diagram on the left shows the folds in the open position. The folds should open like this during breathing. On the right, the folds are shown in the closed position as during speech.

A set of intrinsic and extrinsic muscles of the larynx control the entire functions of the speech, be it oration or singing. Singers by constant practice can build up these muscles to go high pitch or low pitch and modify their singing as per the demands of the pitch.

Mimicry artists put in tremendous efforts to mimic several speeches of several artists and animals by modulating the voice as required. The larynx in general and the vocal cords in particular play a singular role in voice modulation.

Larynx disorders : One can easily identify the quality of voice both in men and women. Some women have voice like men and vice versa. It is vitally important to recognize change in voice due to ageing process or a disease affecting the larynx. Change in voice due to ageing process is typically described as hoarse, shaky, weak, breathy and altered pitch, which we often come across in our day-to-day association with the aged.

There is no way to identify if this change is due to old age or a disease process. This cautions us to be more careful when we notice change in voice in the elderly because it could be due to laryngeal cancer, which could be benign / malignant and hoarseness in the elderly.

Besides cancer of the larynx, other problems affecting the larynx are bacterial /viral infections, occupational problems and congenital problems.

Examination of the larynx commonly called “The Sound Box” is rather difficult because it’s situated deep inside.  ENT Specialists use laryngoscopy (where a mirror is put deep in the throat and the reflections of the larynx in the mirror are studied) for interpretations like inflammation, thickening of cords, destruction of one or both cords and lack of muscular actions due to paralysis of the nerves supplying the muscles of larynx etc. If proper interpretations are not possible an instrument called laryngoscope is used to study various possibilities including malignancy.

voice box closed    voice box open

 

Speech is made possible with the combined effort of several organ systems, starting from the diaphragm and ending with lips. It starts with the lungs, which expels air with force. The larynx takes over by regulating and controlling the airflow and vibrations to provide the needed frequency of sound.

The volumes of the pharynx, oral cavity and the nostrils serve as resonators affecting more subtle and melodious qualities of the voice. The tongue and lips, the last in the combined efforts articulate these vibrations into sounds we hear as speech or songs. In some persons the voice is predominantly nasal due to a dominant role played by the nasal cavity eg. Salma Agha (female singer).

Any degeneration or disruption in any of these combined organ system efforts, along the route from diaphragm to the lips affects the speech. It therefore becomes clear that several conditions affecting these support systems can lead to speech problems (minor to serious problems).

Even if everything is normal and the voice is clear and effective, several factors like smoking, drinking, over-indulgence in beverages might affect voice. Professionals like teachers, singers and orators find it difficult to maintain their voice and must avoid all bad habits if they want their voice to be crystal clear. All said and done there is bound to be a change in the voice as age advances which is not in our control.

 

*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.