The term phonation has slightly different meanings depending on the subfield of phonetics. Among some phoneticians, phonation is the process by which the vocal folds produce certain sounds through quasi-periodic vibration. This is the definition used among those who study laryngeal anatomy and physiology and speech production in general. Phoneticians in other subfields, such as linguistic phonetics, call this process voicing, and use the term phonation to refer to any oscillatory state of any part of the larynx that modifies the airstream, of which voicing is just one example. Voiceless and supra-glottal phonations are included under this definition.
The larynx, commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about 4–5 centimeters in diameter. The larynx houses the vocal cords, and manipulates pitch and volume, which is essential for phonation. It is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The word 'larynx' comes from the Ancient Greek word lárunx ʻlarynx, gullet, throat.ʼ
The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles. There are two recurrent laryngeal nerves, right and left. The right and left nerves are not symmetrical, with the left nerve looping under the aortic arch, and the right nerve looping under the right subclavian artery then traveling upwards. They both travel alongside the trachea. Additionally, the nerves are among the few nerves that follow a recurrent course, moving in the opposite direction to the nerve they branch from, a fact from which they gain their name.
The rima glottidis is the opening between the two true vocal cords anteriorly, and the two arytenoid cartilages posteriorly. It is part of the larynx.
The lateral cricoarytenoid is an intrinsic muscle of the larynx. It attaches at the cricoid cartilage anteriorly, and at the arytenoid cartilage of the same side posteriorly. It is innervated by the recurrent laryngeal nerve. It acts to close the rima glottidis, thus closing the airway.
The posterior cricoarytenoid muscle is a intrinsic muscle of the larynx. It arises from the cricoid cartilage; it inserts onto the arytenoid cartilage of the same side. It is innervated by the recurrent laryngeal nerve. Each acts to open the vocal folds by pulling the vocal fold of the same side laterally. It participates in the production of sounds.
The cricoid cartilage, or simply cricoid or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech.
The cricothyroid muscle is the only tensor muscle of the larynx aiding with phonation. It is innervated by the superior laryngeal nerve. Its action tilts the thyroid forward to help tense the vocal cords.
The arytenoid cartilages are a pair of small three-sided pyramids which form part of the larynx. They are the site of attachment of the vocal cords. Each is pyramidal or ladle-shaped and has three surfaces, a base, and an apex. The arytenoid cartilages allow for movement of the vocal cords by articulating with the cricoid cartilage. They may be affected by arthritis, dislocations, or sclerosis.
Bogart–Bacall syndrome (BBS) is a voice disorder that is caused by abuse or overuse of the vocal cords.
Laryngomalacia is the most common cause of chronic stridor in infancy, in which the soft, immature cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction. It can also be seen in older patients, especially those with neuromuscular conditions resulting in weakness of the muscles of the throat. However, the infantile form is much more common. Laryngomalacia is one of the most common laryngeal congenital disease in infancy and public education about the signs and symptoms of the disease is lacking.
The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of vagus nerve and additionally also receives a sympathetic branch from the superior cervical ganglion.
The aryepiglottic folds are triangular folds of mucous membrane of the larynx. They enclose ligamentous and muscular fibres. They extend from the lateral borders of the epiglottis to the arytenoid cartilages, hence the name 'aryepiglottic'. They contain the aryepiglottic muscles and form the upper borders of the quadrangular membrane. They have a role in growling as a form of phonation. They may be narrowed and cause stridor, or be shortened and cause laryngomalacia.
Vocal cord paresis, also known as recurrent laryngeal nerve paralysis or vocal fold paralysis, is an injury to one or both recurrent laryngeal nerves (RLNs), which control all intrinsic muscles of the larynx except for the cricothyroid muscle. The RLN is important for speaking, breathing and swallowing.
The cricoarytenoid joint is a joint connecting the cricoid cartilage and the arytenoid cartilage. It is a very shallow ball-and-socket joint. It allows for rotation and gliding motion. This controls the abduction and adduction of the vocal cords.
Histology is the study of the minute structure, composition, and function of tissues. Mature human vocal cords are composed of layered structures which are quite different at the histological level.
Laryngeal cysts are cysts involving the larynx or more frequently supraglottic locations, such as epiglottis and vallecula. Usually they do not extend to the thyroid cartilage. They may be present congenitally or may develop eventually due to degenerative cause. They often interfere with phonation.
Endoscopic laser cordectomy, also known as Kashima operation, is an endoscopic laser surgical procedure performed for treating the respiratory difficulty caused as a result of bilateral abductor vocal fold paralysis. Bilateral vocal fold paralysis is basically a result of abnormal nerve input to the laryngeal muscles, resulting in weak or total loss of movement of the laryngeal muscles. Most commonly associated nerve is the vagus nerve or in some cases its distal branch, the recurrent laryngeal nerve. Paralysis of the vocal fold may also result from mechanical breakdown of the cricoarytenoid joint. It was first described in by Kashima in 1989.
Thyroplasty is a phonosurgical technique designed to improve the voice by altering the thyroid cartilage of the larynx, which houses the vocal cords in order to change the position or the length of the vocal cords.
Laryngotracheal reconstruction is a surgical procedure that involves expanding or removing parts of the airway to widen a narrowing within it, called laryngotracheal stenosis or subglottic stenosis.
