Human vocal cords
True vocal cords are located in the middle of the human pharynx, on the right and left sides of it. Representing two, covered with mucous membrane, elastic formations, they are stretched from front to back. Their increased elasticity is due to the presence of connective and muscular tissue in their structure. The space between these formations is called the voice gap. Vocal cords not only participate in the formation of sounds, but also perform the protective function of the lower respiratory tract.
Sounds are formed as a result of convergence, tension and oscillation of ligaments under the influence of air pressure exiting the lungs. It should be noted that the mechanics of sound formation in all vertebrates with a voice device is on average the same. Some mammals do not have it, in some it is developed quite poorly. Many mammals, except true ones, also have false vocal cords. At the person they are located a little above true and in formation of sounds do not participate.
The croaking amphibian ligaments involved in the formation of sounds are located in the lower halves of the "vocal lips".These thick folds of the mucous border the gap along the inner edges of the arytenoid cartilages. Many reptiles are not capable of making sounds. Among them, chameleons and geckos are true bonds.
During breathing, air continuously and smoothly passes through the vocal chink. At the same time, it is rather wide open. The movement of air is due to pressure in the airways. It is the exhalation muscle of a person that creates it. In the process of sound formation, the gap is closed, and the bundles are strained. Under the influence of pressure, the gap opens for a short time and a part of the air leaves it. Then the vocal cords again approach and begin to oscillate. Thus, during the formation of sounds, the current of the air passing through the slit 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 different heights are formed. In the formation of sounds are also involved bronchi, lungs and trachea. To amplify the sounds in the body there is a system of resonators( in man it is the oral and nasal cavities).
Diseases of the vocal cords( inflammation) in a person can often appear suddenly. Typically, this occurs with allergies, viral infections, inhalation of substances that irritate the mucosa. Inflammation can worsen and with overexertion of the voice. Swelling of the mucosa may be accompanied by an increase in the size of the ligaments, a decrease in the cleft. In particularly acute cases, the mucosal edema can lead to a complete closure of the slit. As a result, the supply of air to the lungs stops, and the person begins to gasp.
For the diagnosis, an endoscopic examination method using a special camera is used, which the doctor carefully inserts into the oral cavity or nose. The procedure is performed under local anesthesia, thus preventing vomiting, pain and discomfort in the patient.
Exact study of disorders of the vocal apparatus is performed by stroboscopy. This special method of illumination allows for a slow observation of the frequency of voice vibrations. This method is used in the diagnosis of mechanical and neurological voice disorders, as well as malignant and benign formations less than a millimeter. During the stroboscopy, you can record the diagnostic process on video, which allows you to monitor for a long period and compare the state of the voice device before and after the use of speech therapy or medication. This observation is especially important if an operation is performed on the vocal cords.