True vocal cords are located in the middle region of the human pharynx, on the right and left side of it. Representing two mucosal elastic formations, they are stretched from front to back. Their increased elasticity is due to the presence of connective and muscle tissue in their structure. The space between these formations is called the glottis. The vocal cords not only take part in the formation of sounds, but also perform a protective function of the lower respiratory tract.
Sounds are formed as a result of convergence, tension and oscillations of the ligaments under the influence of air pressure leaving the lungs. It should be noted that the mechanics of the formation of sounds in all vertebrates with a vocal apparatus are the same on average. Some mammals do not have it, in some it is developed rather poorly. Many mammals, besides true ones, also have false vocal cords. In humans, they are located slightly higher than the true ones and do not participate in the formation of sounds.
In croaking amphibians, the ligaments involved in the formation of sounds are located in the lower halves of the “vocal lips”. These thick folds of the mucosa border the gap along the inner edges of the arytenoid cartilage. Many reptiles are not able to make sounds. Among them, true chords are chameleons and geckos.
During breathing, air continuously and smoothly passes through the glottis. However, it is quite wide open. The movement of air is due to pressure in the airways. It is created by the expiratory muscles of a person. In the process of sound formation, the gap is closed, and the ligaments are strained. Under the influence of pressure, the gap opens for a short time and part of the air leaves it. Then the vocal cords come together again and begin to hesitate. Thus, during the formation of sounds, the flow of air passing through the gap is intermittent, and the air itself is in oscillatory motion. Depending on the magnitude and degree of tension of the ligaments, as well as the frequency of air vibrations, sounds of various heights are formed. The bronchi, lungs and trachea also participate in the formation of sounds. To enhance sounds in the body there is a system of resonators (in humans it is the oral and nasal cavities).
Diseases of the vocal cords (inflammation) in a person can often appear suddenly. As a rule, this occurs with allergies, viral infections, inhalation of substances that irritate the mucous membrane. Inflammation can be exacerbated by overstrain of the voice. Swelling of the mucosa can be accompanied by an increase in the size of the ligaments, a decrease in the gap. In especially acute cases, swelling of the mucosa can lead to complete closure of the gap. As a result, the air supply to the lungs ceases, and the person begins to suffocate.
For the diagnosis, an endoscopic examination method is used using a special camera, which the doctor carefully inserts into the oral cavity or nose. The procedure is performed under local anesthesia, thus preventing the patient from vomiting, pain and discomfort.
An exact study of disorders of the vocal apparatus is performed by the method of stroboscopy. This special lighting method allows you to slowly monitor the frequency of voice vibrations. This method is used in the diagnosis of mechanical and neurological voice disorders, as well as malignant and benign tumors of less than a millimeter. When conducting stroboscopy, you can record the diagnostic process on video, which allows you to monitor for a long period and compare the state of the vocal apparatus before and after the use of speech therapy or drug treatment. This observation is especially important if the operation is performed on the vocal cords.