The vocal folds are tissue structures in the larynx that play a large part in voice production. The vocal folds and the glottis between them regulate both the volume and pitch of the voice. However, if the voice is overused, hoarseness and nodules on the vocal folds are the result.
What are the vocal folds?
Colloquially, the vocal folds are often referred to as the vocal cords. However, this is not entirely correct, as the vocal cords represent only part of the vocal folds. The vocal folds are tissue structures located within the larynx in the throat and covered with mucosa. Different sounds can be generated by the vocal muscles located in the vocal folds. When speaking or singing, the ligaments within the vocal folds are made to vibrate, producing different sounds.
Anatomy and structure
The two vocal folds consist of tissue structures within the larynx. In the middle of these vocal folds is a glottis (rima glottidis), which is responsible for producing sounds. Depending on the pitch at which sounds are formed, the glottis can be wide open or largely closed. While the glottis is closed during feeding, so that no swallowing occurs, the glottis is wide open during breathing. This creates the triangular shape characteristic of the glottis. The vocal folds consist of three layers. Inside is the musculus vocalis, also called the vocal muscle. This muscle is capable of producing various sounds by tensing and relaxing. The layer lying on the outside of the vocal muscle is the lamina proporia, which is a layer of connective tissue. The outermost layer is the mucosal layer and consists of a multi-layered, non-keratinized squamous epithelium. This layer of the mucosa contains glands that produce fluid to keep the vocal cords moist and prevent dehydration. Within the layer of lamina proporia is a minimal interstitial space, which is also referred to as the “Reinke space.” Fluid accumulation in this cavity can cause Reinke’s edema. At the rear end of the vocal folds, the two adjusting cartilages are connected so that the position of the vocal folds in relation to each other can be regulated. Above both vocal folds are the pocket folds (plicae vestibulares), which are often also declared as “false vocal cords”. These pocket folds are used to form the voice when the vocal folds are not functional due to certain diseases.
Function and tasks
The vocal folds form the closure of the trachea and are responsible for the formation of the voice. The interaction of the musculus vocalis and the musculus cricothyreoideus creates a control circuit, which makes it possible to regulate the volume and pitch of individual sounds. However, other muscles are also involved. Different sounds can be produced by the different characteristics of the oscillations. When the vocal cords tense, very high-pitched sounds are produced, whereas relaxation of the vocal cords results in low-pitched sounds. When producing high-pitched sounds, the cords vibrate very quickly and can open and close up to 1000 times per second. For low tones, the ligaments vibrate correspondingly slower and do not clash as often. In adults, the vocal cords are larger and longer, so the voice is normally deeper overall than a child’s voice. If the voice is interrupted for a short time by a glottal closure, a glottal stop is produced when this closure is released, which is a significant feature of the German language. This occurs primarily before a vowel-initial sound and before vowel-initial word stems in compound words. The vocal folds are usually examined during a laryngoscopy or with the aid of a laryngoscope by an ear, nose, and throat specialist.
Diseases
Various diseases can severely affect the vocal folds in the larynx. Overall, the vocal cords are very sensitive and can dry out very quickly. All it takes is heating air or a harmless cold. The dehydration causes hoarseness, which can last for several days or weeks. However, in addition to this rather harmless dehydration, there are also serious diseases that can develop on the vocal folds.Laryngitis is an acute form of inflammation of the vocal folds. It usually affects people who have strained their voice too much. However, laryngitis can also be caused by a viral infection. Treatment consists of absolute rest of the voice and taking antibiotics. However, constant strain on the voice can also cause vocal cord nodules. This is often the case with singers. These nodules are elevations at the edge of the vocal folds and disturb the vibration of the vocal folds. A hoarse and smoky voice are consequences of these nodules, which disappear either by rest or by special therapies with a speech therapist. Reinke’s edema occurs when fluid accumulates in the Reinke’s space. The edema causes the vocal folds to swell, resulting in hoarseness and even voicelessness. Probably the stress of the voice, as well as a high tobacco consumption play a role. High tobacco consumption can also cause polyps on the vocal folds, which can be removed with the help of surgery. Tumors, viral infections or surgery can also cause vocal cord paralysis. In this case, the vocal folds can no longer open or close properly. Speech therapy can help to eliminate this. However, if this does not bring improvement, surgery is necessary.
