Archivo de la categoría: FUNDAMENTOS DE LA VOZ

Anatomy, histology and physiology of the vocal cords: Mucosa

Original post in Spanish. Translated by artificial intelligence to achieve a wider diffusion. Please, if you notice errors, contact us in English or Spanish. Thank you for your understanding.

The vocal folds are the two folds within the laryngeal structure at the top of the trachea and are directly responsible for voice production, although they also have other functions such as respiratory (the vocal folds are actively abducted to allow air to pass through) and sphincteric, preventing anything other than air from entering the lungs.

Anatomically, the folds are made up of several layers. From the most superficial to the deepest, we find: the epithelium, the lamina propria (itself divided into superficial, intermediate and deep) and the vocal muscle, the thyroarytenoid. Mechanically, these layers can be divided into three sections: the mucous membrane (made up of the epithelium and the superficial layer of the lamina propria), the ligament (made up of the intermediate and deep layers of the lamina propria) and the vocal muscle.

vocal cordVocal folds layers. Adapted from Gray, 2000.

The layers of the vocal folds have different histological compositions that give them different viscoelastic properties that affect vibration. Changes in their composition, for example due to age, hormones or medication, can alter these proportions and lead to variations in voice quality.

The mucosa is the external structure of the vocal folds, the integrity of which is compromised by the very high rates of impact and traction caused by the vibrations generated by the phonatory act. In the singing voice, these vibrations can reach 1700 or 1800 Hz (vibrations per second). In exceptional cases, such as the Peruvian singer Yma Sumac in the 1940s, even more (C#7 means more than 2200 Hz).

Epithelium and basement membrane
The outermost or superficial layer of the vocal folds is the epithelium, which, according to the RAE (Real Academia Española), “is the animal tissue formed by cells in close contact that lines the surface, cavities and ducts of the organism” (DEL 2014). Epithelial tissues are therefore present throughout the body: skin, oesophagus, trachea, stomach, intestines… What varies is the function of each type of tissue, such as: protecting underlying tissues from injury by mechanical traction, chemical damage, dehydration or infection; absorbing or excreting substances; transporting material, etc.

The vocal folds are covered by a layer of non-keratinised stratified squamous epithelium, the function of which is to protect areas subject to continuous abrasion or impact, such as that received by the vocal folds from phonatory vibration.
Stratification ensures that the layers of cells that make up the epithelium are shed and replaced. The lack of keratin means that this type of epithelium must be constantly moisturised by the body’s secretions to avoid drying out, unlike other keratinised tissues such as the skin, where the high keratin content of the superficial layers ensures that moisture is retained in the inner layers.

Layers-HiranoImage adapted from Hirano (1982) showing the stratified squamous epithelium and the columnar ciliated epithelium.

The basement membrane supports the epithelium and connects it to the superficial layer of the lamina propria. The basement membrane consists mainly of fibroblasts, which are involved in the healing and repair of epithelial cells, and collagen, the protein capable of forming flexible but tensile fibres. The mucosa is the outermost part of the vocal folds and therefore receives the greatest amount of wear and tear and traction from phonatory vibration. The membrane is connected to the lamina propria by fibrils, the number of which is genetically determined, which seems to indicate a certain predisposition to the development of vocal pathologies (Cobeta et al. 2013).

Superficial lamina propria
The superficial lamina propria or Reinke’s space is the first of the three layers that make up the lamina propria, but is part of the vocal mucosa, while the other two form the vocal ligament. It is a highly elastic structure, composed mainly of collagen, to which the basement membrane is attached, but which in turn is not attached to the intermediate lamina propria. This means that the mucosa glides over the ligament independently of its vibration.

The characteristics of flexibility and resistance of the vocal mucosa, in addition to the anatomical independence of the vocal ligament, support the muco-condulatory theory of vocal mechanics discussed earlier in this article.

Furthermore, due to the characteristics of the mucosa, a large proportion of voice disorders originate in this structure.

Hirano-PatologiasThe figures show coronal sections of the vocal folds (divided into mucosa, ligament and muscle) and some of the most common voice disorders. Adapted from Hirano and Bless (1993).

-Broto, J. P. (2006). Otorrinolaringología y patología cervicofacial. Ed. Médica Panamericana.
-Cobeta, I., Núñez, F. y Fernández, S., Patología de la voz, Marge books, 2013.
-Diccionario de la Lengua Española. (2014). Diccionario de la lengua española (23.a ed.). Consultado en
-Gray, S. D., Cellular physiology of the vocal folds. The Otolaryngologic Clinics of North America. V. 30. No. 4. pp 679-98. Aug 2000.
-Hirano M. The role of the layer structure of the vocal fold in register control. Vox Humana. University of Jyvaskyla; 1982. p. 50-62.
-Hirano M, Bless DM. Videostroboscopic examination of the larynx. Singular Publishing Group, San Diego, 1993.

Published by Pilar Lirio, 2016