Vocal Cords

VOCAL CORDS, two paired folds of mucous membrane on the lateral walls of the middle part of the larynx (see), arranged sagittally from front to back one above the other. The upper folds, so-called false vocal cords (chordae vocales falsae, s. spuriae), appear as two elongated ridges; they extend from the anterior angle of the inner surface of the larynx backward, lying at half the height of the arytenoid cartilages. Their free edge, facing the midline, is somewhat concave like a bow and behind is connected with the underlying true vocal cord. The false cords consist of mucous membrane, submucous tissue, and a small muscle bundle which, according to Rudinger, posteriorly enters into the composition of the m. transversi, and anteriorly scatters at the edge of the epiglottis. Due to the presence of this muscle, the false cords have the ability to tense and can approach almost to complete contact, covering to a greater or lesser extent the true cords. They can take an active part in sound production during exertion and during coughing; during the act of swallowing they close. With the complete destruction of the true cords under the influence of a pathological process, the false cords can perform the function of the latter: the resulting sound is although not entirely pure, but sufficiently strong. In the mucous membrane of the false cords there are many mucous glands; they are constructed according to the type of complex tubular glands and belong partly to serous and partly to mixed glands, lying in the submucous fibrous layer. The lower folds bear the name of true vocal cords (chordae vocales verae). They are the most important part of the larynx, since their activity is associated with the respiratory and phonatory functions. The true cords project from the lateral walls of the larynx into its lumen and by contraction of the muscles can come into close contact with each other until complete closure of the glottis, or conversely, diverge with their posterior ends to the sides and form a wide glottis during inspiration and expiration. On cross-section, the cord presents a triangle, the upper side of which faces upward, the inner side looks toward the midline into the lumen of the larynx, and the outer side is attached to its lateral wall; on such a section it is also seen that the thickness of the cord consists of modified mucous and muscular tissue. The main mass of the cord is the muscle embedded in it, the thyroarytenoidus internus (m. thyreo-arytaenoideus internus), which with its anterior end is attached to the midline of the thyroid cartilage, and sometimes also to the conical ligament, and posteriorly to the vocal process of the arytenoid cartilage; thus the muscle is stretched horizontally between the two mentioned cartilages. Due to the fact that this muscle has great importance in phonation, it is also called the vocalis muscle (m. vocalis). The free edge of the true vocal cord, facing into the lumen of the larynx, is much less powerful, is formed of elastic tissue and is called the vocal string (chorda vocalis). The fibers of elastic tissue, more densely laid in the posterior thirds of both cords, extend from the anterior angle of the larynx, beginning from the posterior surface of the thyroid cartilage, horizontally and partly radii backward and are attached to the vocal process of the arytenoid cartilage; the apex of this process in this place shows through the thin mucous membrane as a yellow spot (macula flava). Such a small yellow spot is sometimes also visible on the anterior part of the vocal cords, near their attachment to the thyroid cartilage, in the place where a small cartilage the size of a millet grain is embedded in the thickness of the elastic tissue, however not constantly present; this spot has no practical significance, while the posterior one indicates the boundary where the tissues forming the glottis pass from the membranous part to the cartilaginous part. The elastic part of the true vocal cord is closely fused with the muscular part and forms one whole with it. The free edge of the cord is covered on its upper and lower sides by stratified squamous epithelium; in its superficial layers the cells have a polygonal shape, the boundaries between them are sometimes indistinct, the cells often undergo keratinization; in the deeper layers the epithelial cells in structure approach the principal cells of ciliated epithelium. Mucous glands in the mucous membrane of the true cords are almost entirely absent; only occasionally single mucous glands are found on the lower surface of the cords near the muscular layer. Due to the close fusion of the elastic part of the cords with the muscular part, the cords can change their shape, length, elasticity and tension; their free edge can become thinner or thicker; this explains the occurrence of the basic properties of the voice, concerning timbre, pitch and strength in speech and singing. The length of the true vocal cords in adults varies within wide limits, approximately from 20 to 24 mm in men, from 18 to 20 mm in women and from 12 to 15 mm in children. The male cords are generally thicker and more massive than the female ones. Until the period of sexual maturity, the children's cords change little, but at this age they quickly grow to their final dimensions along with the general growth of the entire larynx; during this period the voice change also occurs - the so-called mutation of the voice. The false and true cords are supplied with blood vessels from the superior laryngeal artery, however the vessels are distributed unevenly: they are less expressed on the true cords and much more numerous on the false ones, therefore during operations on the latter one sometimes encounters strong and persistent bleeding. Lymph vessels on the true cords are very poorly developed; this circumstance has great practical significance, because when they are affected by cancer, the surrounding laryngeal lymph glands do not suffer for a long time and metastases do not occur in other organs. The false vocal cords are much richer in lymph vessels. The vocal cords are supplied with sensory nerves from the superior laryngeal nerve. The muscles associated with the movement of the vocal cords receive motor nerve fibers from both the superior and inferior laryngeal nerves, with only one muscle, the tensor of the true vocal cords - the thyroarytenoid muscle, being supplied from the former. It is of interest that the inferior laryngeal nerve innervates at the same time the posterior cricoarytenoid muscle, which widens the glottis, and at the same time the muscles that close it. The function of the vocal cords is respiratory and phonatory. The respiratory function consists in regulating the width of the glottis, which can be widened to a greater or lesser degree; so for example during forced deep inspiration the vocal cords diverge to the sides to the maximum. These movements of the cords occur due to the mobility of the arytenoid cartilages, to which the posterior ends of the cords are attached, under the influence of contraction of the posterior cricoarytenoid muscle; this is the only muscle for abduction of the cords. The closing of the vocal cords (adduction) is performed mainly with the help of the antagonist of this muscle - the lateral cricoarytenoid muscle. Even during quiet breathing, the vocal cords do not remain immobile: they automatically approach somewhat during inspiration and slightly diverge during expiration. The glottis is also closed reflexively during swallowing by means of a center located in the medulla oblongata. Lack of oxygen leads to wide opening of the glottis, while spoiled, unsuitable for breathing air causes reflexive closure of the cords. During coughing, the vocal cords approach the midline in a relaxed state. The phonatory function of the cords is performed according to the principle of a vibrating reed in an organ pipe: the closed vocal cords, under the influence of increased air pressure in the trachea and bronchi, come into a state of vibration and, shaking the air, produce sound. Regarding the nature of these vibrations of the true vocal cords, there were different opinions, and at present it has been established, mainly by means of stroboscopic observations, that when producing sound the cords move in the transverse direction, and not from top to bottom, as was thought before; the periodicity of the closing and opening of the cords depends on the uniform ruptures of the air flowing from the trachea through the narrowed glottis. The pitch of the voice is related to the degree of tension of the cords, which is achieved by the anterior cricothyroid muscle, which, by displacing the thyroid cartilage forward with the arytenoid cartilages immobile, stretches the cords like a string. The more tense the cords, the higher the pitch of the voice. The timbre of the voice, besides many causes lying outside the larynx, depends to a greater degree on the physical properties of the vocal cords, on their individual structure (thickness, elasticity, length, etc.), as well as on the ability of the vocal cords to change their shape and tension under the influence of the thyroarytenoid muscles located in their thickness. The possibility of giving the voice different sound shades is connected with the variety of variations in the functioning of these muscles. The strength of the voice depends on the magnitude of the amplitude of vibration of the cords and is in close relationship with the air pressure in the trachea and bronchi during phonation. The question of whether the pressure automatically adapts to the mode of the vocal cords or, conversely, the activity of the cords depends entirely on the magnitude of the air pressure, remains unresolved.

It has been observed that the strength of the voice is not in proportional relationship to the strength of pressure, therefore the conditions for the formation of vocal strength are not similar to the process occurring in a reed pipe, where the reed is completely subject to air pressure.--All the mentioned properties of the voice can be disturbed even with the slightest changes in the mucous membrane, musculature, and nervous apparatus of the V.C. During conversational speech or during the so-called chest voice, the cords vibrate with their entire mass, while in falsetto only their thinned edges participate. During whispering, the vocal cords do not come into a vibratory state and close incompletely, so that a slit remains between them. In accordance with the smaller size of the V.C., in women the voice is an octave higher than in men, during speech and singing. The study of the V.C. is carried out by means of the laryngoscopy method (see). For a more subtle observation of the movements of the V.C. during phonation, the stroboscopy method is used (see).--The pathology of the V.C., both true and false, most often concerns the mucous membrane, which can present different forms of inflammatory changes, both acute and chronic, of infectious and non-infectious origin; in these cases, the lesion of the cords is usually a partial manifestation of the disease of the entire larynx, however, often the entire disease can be concentrated only on the true or false cords. Sometimes changes in the mucous membrane of the V.C. are the first sign of an impending general disease of the larynx. One or both cords can be affected entirely or partially. In addition to the mucous membrane, the muscular part of the V.C. can also be affected by disease, and then the disease proceeds in the form of weakening, paresis, or complete paralysis; however, such phenomena of weakening of muscular activity more often occur due to suffering of the motor nerves supplying the larynx. A large chapter in the pathology section of the V.C. is occupied by neoplasms, which can be benign and malignant. In some cases, the function of the V.C. is disturbed due to disease of neighboring areas, for example, immobility of the true cord can occur in ankylosis of the arytenoid-cricoid cartilage. In acute laryngitis, the true vocal cords usually appear as red streaks during laryngoscopic examination, thickening of their edges is observed, often they are found to be covered by swollen false cords. In severe inflammation in some cases, hemorrhage is noted on the true cords, defects of the epithelium and disturbance of their motor ability are observed. The cords often appear dry, sometimes accumulation of a viscous secretion is noted, which stretches between the right and left cords in the form of threads. In some influenza-like forms of inflammation, as well as in diphtheria, white-colored deposits form on the true or false cords. In chronic laryngitis, the picture of lesions of the true and false cords can be extremely diverse depending on the nature of the disease. Persistent thickenings can be either as a result of edema of the cord tissue or due to hyperplastic growths. If the thickening of the flat epithelium of the true cords becomes significant, such changes are called pachydermia; often these thickenings are nodular (chorditis nodosa) or are papillomatous tumors, which is observed mainly in the area of the vocal process of the arytenoid, subjected to constant pressure during phonation. - The diversity of pathological changes is especially great in tuberculous lesions of the true and false cords. The most characteristic sign of the initial stage of the catarrhal form of tbc of the larynx is unilateral reddening of the true V.C., which with time passes to the other side. Infiltrates of tuberculous origin can be on both true and false cords, with the most diverse localization and external form, and they appear as diffuse thickenings or limited tumors - tubercles. Due to the breakdown of infiltrates on the true and false cords, tuberculous ulcers form, which often take the form of a crater with jagged, eroded edges. A characteristic feature of these ulcers is their tendency to form irregular red granulations, which can grow along the edges like papillomatous tumors. Among benign tumors on the true cords, polyps or fibromas are most common; usually they are located on the middle or third and appear as a round tumor sitting on the free edge with a pale-colored smooth surface. Papillomas and angiomas also preferably localize on the true cords. Malignant tumors of the V.C. most often manifest in the form of cancer; in almost 2/3 of all cases of laryngeal diseases, the true vocal cords are the starting point for the tumor. During laryngoscopic examination in the beginning of cancer of the cords, a small redness is found on one side; soon a swelling appears at this place, which is either limited or turns into a bumpy tumor of white or matte-red color, often lying among normal or slightly inflamed tissue of the cord. In many cases, it is clearly visible that the tumor is not superficial, but is firmly rooted in the substance of the cord. In the further course, the tumor goes beyond the limits of the cord and spreads to the false cord and to half of the larynx. A characteristic feature of cancer is the appearance of immobility of the affected cord, which apparently depends on changes in the arytenoid joint. In structure, these cancers are squamous cell carcinomas. Sarcomas also develop on the true vocal cords and have the appearance of a clearly limited round or lobulated tumor. They are rare. Great practical importance is attached to motor disorders from the side of the true V.C., since this can disturb both the respiratory and phonatory functions of the larynx. These disorders of the movements of the cords are caused either by lesions of the nervous system or changes in the muscular tissue itself and are expressed in the form of increased function or suppression and complete destruction of it. Increased excitability of the neuromuscular system leads to spasms of the V.C., and these spasms are usually directed towards closing the glottis. As a physiological phenomenon, spasm of the V.C. occurs with irritation of the laryngeal mucous membrane, for example when lubricating the larynx or when a foreign body enters it, when inhaling irritating vapors and gases, therefore it occurs reflexively. In children, spasm of the glottis is often observed in early age on the basis of rickets, poor nutrition, adenoids, with whooping cough, spasmophilia, etc. (see Laryngospasm). In adults, spasm of the vocal cords - see Larynx, pathology of the larynx and Laryngospasm. Mutation of the voice during the period of sexual maturity sometimes also proceeds with phenomena of strong tension of the voice due to spasm of the laryngeal muscles during phonation. Decrease in motor function of the V.C. proceeds in the form of pareses and paralyses of them, and these disorders depend either on changes in the muscles connected with the V.C., or on suffering of the nervous system (see Larynx, pathology of the larynx). Neuropathic paralyses of the V.C. can be of cerebral, bulbar, and peripheral origin, organic and functional. A characteristic sign of organic suffering of the nerves of the V.C. is the fact that first of all the abductor muscle (m. posticus) is affected, from which the V.C. become immobile in the median position, while in functional ones, on the contrary, they cannot close (in hysteria). In bilateral paralysis of the recurrent nerve, both V.C. stand along the median line of the larynx, and the narrow slit between them only slightly widens with strong inspiration; if this suffering develops rapidly, then severe difficulty in breathing can occur, and for saving life tracheotomy is required. - Myopathic paralyses are usually associated with mechanical conditions, for example, they occur due to inflammatory infiltration of the mucous membrane, ankylosis of joints, tumors, and scar changes. This also includes isolated pareses of individual laryngeal muscles, arising under professional conditions as a result of overstrain of the voice with excessive tension. Such myopathic paralyses and pareses can be temporary and disappear without a trace, in other cases it leads to atrophy of muscular tissue or its fatty and connective tissue degeneration. From the laryngoscopic picture, it is impossible to say whether the movement disorders depend on suffering of the muscle or nerve, usually the constrictors suffer. Close to these sufferings is a peculiar disease of the voice, associated with changes in the activity of the neuromuscular apparatus - dysphonia, or phonasthenia, in which no motor disturbances are observed from the side of the V.C., while a very noticeable disorder of the vocal function occurs. The first symptoms are noted by the patient himself, who feels that his voice becomes less enduring, quickly tires, phonation is accompanied by a number of paresthesias in the form of tickling, scratching in the throat, sensation of dryness and pain in the throat. Then the voice gradually refuses to serve, high tones disappear, the timbre changes, the purity of sound is disturbed, hoarseness and huskiness appear, and finally the voice is lost not only for singing but also for speech.

The cause of the disease lies in intensive vocal exercises, which is why the disease is usually observed in singers, teachers, orators, etc. Most authors compare the origin of phonasthenia with the development of occupational diseases in workers engaged in muscular labor, which also occur without objective changes. On a professional basis, acute and chronic inflammations of the vocal cords occur in the form of diffuse or limited redness or thickening of the mucous membrane; hemorrhage into the substance of the cords or into the muscle is also observed with strong vocal tension, when taking high tones, screaming, etc. In those who sing a lot and speak loudly, so-called singer's nodules often appear on the vocal cords as a result of chronic trauma to the edges of the cords. These nodules are small neoplasms of connective tissue or epithelial origin and are located symmetrically on the free edges of both vocal cords, at the boundary between their anterior and middle thirds. The peculiarity of the nodules is that they can appear on a cord that appears completely healthy. Nodules are also observed in children who scream a lot and loudly.

L. Rabotnov. CLOT-a product of postmortem coagulation of blood or plasma or serous exudate-represents a gelatinous, elastic formation with a shiny, smooth surface. The color of the clot ranges from light yellow to red, and in blood clots, two layers are often distinguishable-the upper light yellow and the lower red. Microscopically, the clot consists of delicate, interwoven fibers of fibrin with blood elements included between them. Blood clots form as a result of the so-called spontaneous coagulation of blood, which after death of the organism is observed in the cavities of the heart and in the lumens of vessels, and during life-in the mass of blood that has escaped during bleeding, both into the external environment and into tissues and body cavities (mechanism of blood coagulation-see Blood). It is practically important during autopsy, especially when analyzing the cause of death, to be able to distinguish clots from thrombi, since in the formation of the latter, blood coagulation processes also take place, but they occur during life and have a different origin (see Thrombus, thrombosis). Apparently guided by the fact that clots in tissues during bleeding can form during life, some authors call them extravascular thrombi. As a rule, differentiation of clots from thrombi is quite easy; the former are elastic, not fused with the vessel wall, the latter are crumbly, with a rough surface, attached to the vessel wall over some extent. In some cases, when thrombus formation (e.g., in the pulmonary artery) is followed by instantaneous death, the external resemblance of such a thrombus to a clot is extremely great. It is also elastic, not fused with the wall. Sometimes, by cutting such a thrombus into small pieces, it is possible to find somewhere in its depth a small dry embolus that has caused antemortem blood coagulation. The color of the clot depends on the rate of blood coagulation: with rapid coagulation, erythrocytes give the clot a red color; if the erythrocytes have time to settle, then the clot is either light or two-layered (the fate of clots in tissues and cavities-see Hemorrhage).-Some authors (Ribbert, Tendeloo) believe that clots in vessels form in the agonal period, but most authors do not adhere to this view, based on data obtained from early autopsies: in such autopsies, performed for example several minutes after death, clots are usually absent. The speed of clot formation in the corpse is often associated with the nature of the disease and death; for example, in those who died with signs of severe asphyxia, clots may not form at all due to the richness of the blood in carbon dioxide. Similarly, the very nature of the clot in the corpse changes depending on the premortem composition of the blood, certain diseases. Thus, with rapid death, clots are usually red. With increased blood coagulability, for example, in the cavities of the heart, predominantly light clots are observed (croupous pneumonia, peritonitis, etc.). In serous exudates, clots form as a result of cooling of the corpse (just as they form in the exudate that has been secreted).