Name = Vocal folds
Latin = plica vocalis
GraySubject = 236
GrayPage = 1079
Caption = Laryngoscopic view of the vocal folds.
Caption2 = Abduction and
Precursor = |Sixth pharyngeal arch System =
Nerve = |N. laryngeus recurrens and N. laryngeus superior Lymph =
MeshName = Vocal+Folds
MeshNumber = A04.329.364.737
DorlandsPre = p_24
DorlandsSuf = 12649423
The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of
mucous membranestretched horizontally across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation. [Titze, I. R. (2008). The human instrument. Sci.Am. 298 (1):94-101. PM 18225701] [Titze, I.R. (1994). Principles of Voice Production, Prentice Hall (currently published by NCVS.org), ISBN 978-0137178933.] [cite book
last = Maton
first = Anthea
coauthors = Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright
title = Human Biology and Health
publisher = Prentice Hall
date = 1993
location = Englewood Cliffs, New Jersey, USA
isbn = 0-13-981176-1]
Open during inhalation, closed when holding one's breath, and vibrating for speech or singing (oscillating 440 times per second when singing A above
middle C); the folds are controlled via the vagus nerve. They are white because of scant blood circulation.
Vocal fold oscillation
The larynx is a major (but not the only) source of sound in
speech, generating sound through the rhythmic opening and closing of the vocal folds. To oscillate, the vocal folds are brought near enough together such that air pressure builds up beneath the larynx. The folds are pushed apart by this increased subglottal pressure, with the inferior part of each fold leading the superior part. Under the correct conditions, this oscillation pattern will sustain itself. In essence, sound is generated in the larynx by chopping up a steady flow of air into little puffs. [Titze, I. R. (1988) The physics of small-amplitude oscillation of the vocal folds. J.Acoust.Soc.Am. 83 (4):1536-1552, PM:3372869.]
The perceived pitch of a person's voice is determined by a number of different factors, not least of which is the
fundamental frequencyof the sound generated by the larynx. A person's natural fundamental frequency is influenced by many factors, including the length, size, and tension of the vocal folds. In an adult male, this frequency averages about 125 Hz, adult females around 210 Hz, in children the frequency is over 300 Hz. Depth-Kymography[Depth-Kymography: High-speed calibrated 3D imaging of human vocal folds vibration dynamics, Nibu A George et.al., Physics in Medicine and Biology, 53, 2667-2675 (2008) ] is an imaging method to visualize the complex horizontal and vertical movements of vocal folds.
The vocal folds generate a sound rich in
harmonics.Some singers can isolate some of those harmonics in a way that is perceived as singing in more than one pitch at the same time -- a technique called overtone singing.
The folds are located below the
epiglottis, the lid-like flap that separates the windpipe from the esophagus.
The folds are located just above the trachea or the windpipe which travels from the lungs. Food and drink does not pass through the folds but is instead taken through the
esophagus, an unlinked tube. Both tubes are separated by the tongue and an automatic gag reflex. When food goes down through the folds and trachea it causes choking.
Folds in both sexes are within the
larynx. They are attached at the back (side nearest the spinal cord) to the arytenoid cartilages, and at the front (side under the chin) to the thyroidcartilage. Their outer edges (as shown in the illustration) are attached to muscle in the larynx while their inner edges, or margins are free (the hole). They are constructed from epithelium, but they have a few muscle fibres in them, namely the vocalis musclewhich tightens the front part of the ligament near to the thyroid cartilage. They are flat triangular bands and are pearly white in color. Above both sides of the vocal cord (the hole and the ligament itself) is the "vestibular fold" or "false vocal fold," which has a small sacbetween its two folds (not illustrated).
Men and women have different vocal fold sizes. Adult male voices are usually lower pitched and have larger folds. The male vocal folds (which would be measured vertically in the opposite diagram), are between 17 mm and 25 mm in length. [Titze, I.R. (1994). Principles of Voice Production, Prentice Hall (currently published by NCVS.org), ISBN 978-0137178933.]
The female vocal folds are between 12.5 mm and 17.5 mm in length.
Folds are pearly white in color - whiter in females than they are in males.
The difference in vocal fold size between men and women means that they have differently pitched voices. Additionally, genetics also causes variances amongst the same sex, with men's and women's voices being categorised into types.
"Vocal cords," a term commonly used to refer to the vocal folds, is also spelled 'vocal chords', possibly due to the musical connotations or to confusion with the geometrical definition of the word "chord". While both spellings are historically correct, standard American spelling is 'vocal cords'. [http://www.bartleby.com/68/47/1247.html Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.] According to the Oxford English corpus, contemporary writers opt for vocal chords instead of vocal cords 49% of the time. [http://blog.oup.com/2007/10/corpus-2/ OUP blog] [http://abcnews.go.com/Video/playerIndex?id=3737179 ABC News video] The 'vocal chords' variant has long been accepted in the United Kingdom (along with other anatomical uses like 'spinal chord'). Even in the United States, both variants can be found from early on, and it was only later on that American writers settled on 'vocal cords' as the standard version. [http://blog.oup.com/2007/10/corpus-2/ OUP blog] [http://www.jstor.org/view/00274666/ap030508/03a00160/0 The Musical Times issue April 1946.]
False vocal folds
The vocal folds discussed above are sometimes called 'true vocal folds' to distinguish them from the false vocal folds. These are a pair of thick folds of mucous membrane that protect and sit slightly superior to the more delicate true folds. They have minimal role in normal
phonation, but are often used in musical screaming and the death gruntsinging style. They are also used in Tuvan throat singing.
The false folds are also called
vestibular folds and ventricular folds. They can be seen on the diagram above as "ventricular folds".
False vocal folds, when surgically removed, can regenerate completely.
vocal fold nodule
vocal cord dysfunction
* [http://www.ncvs.org/ National Center for Voice and Speech's official website]
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