The Motor Fibers of Galen's Anastomosis in the Canine Larynx

International Journal of Morphology, 2011

The vocal muscle is a striated muscle with important functions in the emission of laryngeal sound and physiology of the voice. Therefore the knowledge of its constitution is the basis for the prevention and management of voice disorders. We used 10 samples from the middle third of vocal muscles obtained from autopsies of 6 male and 4 female subjects aged between 36 and 71 years. The samples were analyzed with BA-F8 monoclonal antibody to slow type I fibers, and antimyosin HC monoclonal antibody and antimyosin fast clone MY-32 antibody for types IIA, IIB, IIX, and neonatal fibers. We determined the distribution of the muscle fiber types and morphometric characteristics, evaluating the differences by sex and age group. The human vocal muscle presented a heterogeneous formation with a predominance of type II fibers at 51.99%, while type I fibers reached 48.01%; this difference was significant (p <0.05). Comparing fiber subtypes IIA and IIX, there is a slight predominance of type IIX fibers, although this is not statistically significant (p>0.05). In conclusion, the human vocal muscle the fibers were predominantly type II fast.

Journal of the Neurological Sciences, 1997

The innervation of laryngeal muscle fibers was appraised in adult humans. Sixteen intrinsic laryngeal muscles were dissected during the autopsy of 4 adults (41-71 years old). Longitudinal serial frozen sections, 60 mm thick, of the whole muscles were double-stained for cholinesterase activity and axonal visualization. About 945 endplates per muscle were analysed using light microscopy. The neuromuscular junctions were always scattered throughout the whole muscles. Most of the muscle fibers showed a single neuromuscular junction, but multi-innervated fibers were found in all of the muscles. Their number was highest in interarytenoid muscles (21% of all the fibers). The distance between multiple neuromuscular junctions was most frequently less than 150 mm. Two neuromuscular junctions were frequently displayed, opposite one another, particularly in thyroarytenoid muscles, and this unusual feature seems specific for laryngeal muscles. The innervation of all of the muscle fibers was exclusively found to be unineuronal, with multi-innervated fibers being innervated by a single axon. Distal axonal degeneration occurred with aging, resulting in a loss in the number of multi-innervated muscle fibers. © 1997 Elsevier Science B. V.

Anatomy and Embryology, 1992

The aim of the present study was to further subdivide the type II fibers of the human thyroarytenoid and posterior cricoarytenoid muscles by means of a modified myosin ATPase reaction. In order to understand the functioning of these highly strained muscles better, it is important to know the respective percentage of fatigue-resistant type IIA fibers and fatigable type IIB fibers. The material comprised the larynges of seven laryngectomized males aged between 45 and 70 years and four laryngectomized females aged between 39 and 72 years. After having been frozen in nitrogen, 10-gin-thick sections were cut from the laryngeal muscles in a cryostat. The pH-lability of the enzyme that can be utilized in a classical myosin ATPase reaction permits a differentiation between fiber types I, IIA and IIB. Evidently, this is not possible with every human muscle. The fiber types IIA and IIB of the thyroarytenoid and the posterior cricoarytenoid muscles could be clearly distinguished by means of the inhibition reactivation myofibrillar ATPase technique. Using this method, the myosin ATPase enzyme was initially inhibited by hydroxymercuribenzoate and subsequently reactivated by cysteine. Regarding the incidence of type I and IIA fibers, there was a statistically significant difference between the thyroarytenoid and the posterior cricoarytenoid muscles. The type IIA fiber content was statistically significantly higher in the arytenoid muscle than in the posterior cricoarytenoid muscle. The percentage of type IIB fibers was low, not only in the thyroarytenoid muscle and the posterior cricoarytenoid muscle but also in the other laryngeal muscles. The share of fiber types I, IIA and IIB in the thyroarytenoid muscles varied greatly from one patient to another. This was also true for the other laryngeal muscles. This aspect may be especially significant with regard to an individual's vocal character and vocal fatigability under stress.

The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 2006

Vertebrates are capable of producing a variable sound spectrum. In mammals, lissamphibia, and reptiles, the larynx is the vocal organ responsible for sound production, whereas in birds it is produced by the syrinx, an avian organ located at the base of trachea. The distribution of neuromuscular junctions responsible for the fine control of laryngeal muscle (LM) and syringeal muscle (SM), although studied with some detail in human LM, remains mostly unknown in other vertebrates. In the present study, we analyzed the distribution of motor end plates (MEPs) in LM/SM of different vertebrate classes using the histochemical detection of acetylcholinesterase: the thyroarytenoid and cricoarytenoid LM of mammal (human, rat, and rabbit) and cricoarytenoid LM of nonmammalian (frog and avian) species and the tracheobronchial SM of rooster and pigeon. In humans and frogs/avians, MEPs were distributed diffusely along, respectively, the thyroarytenoid-cricoarytenoid and the cricoarytenoid LM fibers, whereas in rats and rabbits, MEPs were concentrated in a transverse band located in the middle of thyroarytenoid and cricoarytenoid muscle fibers. In roosters and pigeons, MEPs were distributed diffusely along SM fibers. The highly diffuse MEP distribution along human thyroarytenoid and cricoarytenoid fibers indicates that these muscles can markedly change their degree of contraction, which may contribute for the large range of different sounds produced by human vocal folds. The same rationale was applied to discuss the possible functional significance of the morphological distribution of MEPs along the LM/SM of the other vertebrates analyzed.

Objectives/Hypothesis: Laryngeal muscles are specialized for fine control of voice, speech, and swallowing, and may differ from limb muscles in many aspects. Because muscles and their controlling motor neurons communicate via neuromuscular junctions (NMJs), we hypothesized that NMJs in laryngeal muscles have specialized characteristics different from limb muscles.

Otolaryngology - Head and Neck Surgery, 1998

This report describes the first known investigation of canine laryngeal muscle in which single fibers were dissected and their myosin heavy chain (MHC) isoform content was analyzed. Both SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot techniques were used. The data from single fiber SDS-PAGE indicate that the lateral cricoarytenoid (LCA) is predominantly a fast muscle composed of the following MHC isoforms: Type I, 16.3%; Type IIA, 71.3%; Type IIX, 10.4%; and Type IIB, 2.0%. The results reveal a phenomenon that, to our knowledge, has not been previously described for laryngeal muscle: the presence of two or more MHC isoforms in a single canine LCA muscle fiber. A large number (41%) of muscle fibers coexpressed two or more MHC isoforms. The three most common patterns of coexpression were Type IIA/IIX (72%), Type IIA/I (16%), and Type IIA/IIX/I (8%). Interestingly, the fast Type IIX MHC isoform was typically present with other isoforms and rarely found by itself in ...

European Surgery, 2003

Background: Since the beginning of the Christian era, numerous reports have dealt with the construction and functional organization of the larynx, thus stressing its role as the keystone of vocalization in vertebrates. The purpose of this review is to provide a comprehensive summary of basic anatomical facts and to point out certain new aspects of the innervation of laryngeal muscles. Methods: The data presented herein were collected from a preliminary gross anatomical study performed in six human individuals at our institute, and from published literature. Results: The basic framework of the human larynx is composed of the hyaline thyroid, cricoid and arytenoid cartilages, the fibroelastic epiglottis and the hyoid bone. Two pairs of synovial articulations, i.e. the cricothyroid and cricoarytenoid joints, provide the mobility needed to adjust the tension of the vocal ligaments. The intrinsic laryngeal muscles may be divided into three functional groups: (i) muscles varying the rima glottidis (the transverse arytenoid as well as the lateral and posterior cricoarytenoid muscles); (ii) muscles regulating tension in the vocal ligaments (i.e. the cricothyroid, posterior cricoarytenoid as well as the compound thyroarytenoid and vocalis muscles) and (iii) muscles modifying the laryngeal inlet (the so-called 'sphincter aditus', which is formed by the oblique arytenoid and aryepiglottic muscles and counteracted by the thyroepiglottic muscle). They are innervated by the superior and inferior laryngeal nerves branching off the vagus nerve. The external branch of the superior laryngeal nerve exclusively supplies the cricothyroid muscle. There is strong evidence that the lateral cricoarytenoid and the thyroarytenoid muscles are solely supplied by the inferior laryngeal nerve. All other intrinsic laryngeal muscles seem to receive motor fibres either from both laryngeal nerves or from the internal branch of the superior laryngeal nerve alone. Conclusions: Thus, the traditional concept of motor innervation of the larynx seems to be out of date. In fact, the internal branch of the superior laryngeal nerve should no longer be seen as purely sensory but rather -as also the inferior laryngeal nerve -as a mixed nerve containing sensory as well as motor fibres. (Eur. Surg. 2003; 35:250-258) Funktionelle Anatomie der menschlichen Kehlkopfmuskeln Zusammenfassung: Grundlagen: Schon seit dem Beginn unserer Zeitrechnung haben sich viele Forscher mit den verschiedenen Aspekten des Aufbaus und der funktionellen Organisation des Kehlkopfes auseinandergesetzt. Dieses Interesse resultiert aus seiner bedeutenden Position als Grundlage der Stimmgebung bei Mensch und Tier. Aufgabe dieser Übersichtsarbeit ist es, eine Zusammenfassung der anatomischen Fakten zu präsentieren und einige neue Aspekte der motorischen Innervation der Kehlkopfmuskeln aufzuzeigen. Methodik: Die vorliegenden Daten entstammen einer noch nicht abgeschlossenen anatomischen Studie, die an sechs menschlichen Individuen an unserem Institut durchgeführt wurde. Weitere Angaben wurden der zu diesem Thema reich vorhandenen Literatur entnommen. Ergebnisse: Das Skelett des Kehlkopfes wird von den hyalinen Schild-, Ring-und Stellknorpeln, dem aus elastischem Knorpel bestehenden Kehldeckel und dem Zungenbein gebildet. Zwei paarige, synoviale Gelenke, die Artt. cricothyroideae et crico-arytaenoideae ermöglichen die für die unterschiedliche Spannung der Stimmbänder nötige Beweglichkeit. Die intrinsischen Kehlkopfmuskeln können in drei funktionelle Gruppen gegliedert werden: (i) Muskeln, die die Breite der Stimmritze variieren (M. arytaenoideus transversus und die Mm. crico-arytaenoideus lateralis et posterior); (ii) Muskeln, die die Spannung in den Stimmbändern regulieren (die Mm. cricothyroideus et crico-arytaenoideus posterior sowie der M. thyro-arytaenoideus mit seiner medialen Abspaltung, dem M. vocalis); und (iii) Muskeln, die die Weite des Aditus laryngis beeinflussen (der sogenannte Sphincter aditus, der von den Mm. arytaenoidei obliqui und den Mm. ary-epiglottici gebildet wird und dem der M. thyro-epiglotticus entgegenwirkt). Alle Muskeln werden von Ästen des Nervus vagus, den Nn. laryngei sup. et inf. innerviert. Der Ramus externus des N. laryngeus sup. versorgt ausschließlich den M. cricothyroideus. Es gibt starke Anzeichen dafür, daß nur der M. crico-arytaenoideus lateralis und der M. thyro-arytenoideus vom N. laryngeus inferior motorische Fasern bekommen. Alle anderen intrinsischen Kehlkopfmuskeln dürften entweder gemeinsam vom N. laryngeus inferior und vom Ramus internus des N. laryngeus superior oder ausschließlich von letztgenanntem Nerven versorgt werden.

Peptides, 2004

TFF peptides (formerly P domain peptides, trefoil factors) are typical secretory products of mucin-producing cells and are thought to influence the rheological properties of mucous gels. We investigated the localization of these peptides in the human false vocal folds of the larynx, also known as the ventricular folds or vestibular folds. An analysis of TFF peptide mRNA by RT-PCR and TFF protein by Western blot detected TFF1 and TFF3, but not TFF2. Immunohistochemistry revealed TFF1 to be associated with the secretory product of goblet cells and mucous parts of subepithelial seromucous glands. TFF3 occurred in columnar epithelial cells of the mucosa and in serous cells and excretory duct cells of seromucous glands. These peptides may play a role in the rheological function of mucus secreted onto the true vocal folds and are thus important constituents of vocal production.

Objectives/Hypothesis: Laryngeal muscles are specialized for fine control of voice, speech, and swallowing, and may differ from limb muscles in many aspects. Because muscles and their controlling motor neurons communicate via neuromuscular junctions (NMJs), we hypothesized that NMJs in laryngeal muscles have specialized characteristics different from limb muscles.

Annals of Otology, Rhinology & Laryngology, 1993

Speech is initiated in the larynx by an alteration of the airstream that accompanies contraction of the intrinsiclaryngeal muscles. Electromyography (EMG) ofhuman laryngeal muscles confirms that there is an increase in the activity of the interarytenoid (lA), cricothyroid (CT), thyroarytenoid (TA), and lateral cricoarytenoid (LCA) muscles before and during phonation. 1-3 This study will focus on the activity of the IA muscle during phonation in the canine model.