Composition of the extracellular matrix in human cricoarytenoid joint articular cartilage.
The extracellular matrix of the human cricoarytenoid joint articular cartilage is involved in different pathological changes. Interestingly, in contrast to the limb joints, the extracellular matrix composition of the healthy cricoarytenoid joint articular cartilage has not yet been elucidated except by some light microscopical investigations. The present study investigates the extracellular matrix components of the cricoarytenoid joint articular cartilage by means of light microscopy, immunohistochemistry, transmission electron microscopy and scanning electron microscopy and compares them with the limb joints for a better understanding of their involvement in joint disease. Chondrocytes near the joint surface of the cricoid and arytenoid cartilage differ from chondrocytes of deeper cartilage layers. The extracellular matrix of the articular cartilage contains chondroitin-4-sulfate, chondroitin-6-sulfate and keratansulfate as well as collagen types II, III, VI, IX and XI. Type-III-collagen shows a special distribution throughout the joint cartilage. In deeper cartilage layers, type-III-collagen occurs only pericellularly; in higher cartilage layers type-III-collagen is also located territorially and interterritorialy in small amounts. Scanning and transmission electron microscopy have revealed the articular surface of the cricoid and arytenoid cartilage to consist of a network of irregularly organized collagen fibrils, which are lined by a layer of electron dense material. The network coats subjacent collagen bundles which descend obliquely downward and intermingle at right angles in the middle part of the articular cartilage with collagen bundles of the deeper cartilage zones. The articular cartilage surface shows structural characteristics which differ from the underlying cartilage. The superficial electron dense layer possibly plays a role in the lubrication of the articular cartilage surface. The alignment of the fibrillar structures in the articular cartilage of the cricoarytenoid joint varies from those of the limb joints based on the different strain occurring during arytenoid movement. Nevertheless, the human cricoarytenoid joint articular cartilage can be compared with the joints of the limbs despite its extracellular matrix composition and its involvement in joint pathology. Evidence of type III collagen in the outermost layer of the articular cartilage of the cricoarytenoid joint presents a peculiarity, which has yet not be demonstrated in the articular cartilage of limb joints. (+info)
New insights into the pathomechanism of postintubation arytenoid subluxation.
BACKGROUND: Impaired movement of the cricoarytenoid joint with hoarseness and immobility of the vocal ligament can occur as a consequence of endotracheal intubation. The biomechanics and pathomechanism of cricoarytenoid subluxation have not been demonstrated to date. METHODS: The present study attempts to simulate the trauma that has been associated with arytenoid cartilage subluxation in intubation trials on 37 unfixed larynges in cadavers from persons aged 25 to 89 years. Larynges were intubated or extubated according to former conceptions of arytenoid subluxation, which assume that the arytenoid tip enters the lumen of the tracheal tube, or that a deflection of the arytenoid occurs during withdrawal of the endotracheal tube with the cuff of the tube only partially deflated. Also, manual attempts were carried out to subluxate the arytenoid cartilage. Subsequently after dissecting the left and right cricoarytenoid joint from each larynx, the morphologic changes induced experimentally were analyzed using gross microscopic and histologic methods. RESULTS: Within the scope of the experiment, it proved impossible to produce any subluxation of a cricoarytenoid joint. Histologic analysis revealed injuries of synovial folds, joint-surface impressions of the articular cartilage, and fractures in the area of the subchondral bone in some joints. CONCLUSIONS: Based on the morphologic results, it was concluded that intubation trauma of the cricoarytenoid joint does not cause subluxation per se, but rather that formation of a hemarthros or fractures of the joint bodies lead to fixation of the joint surfaces in an abnormal position. Subsequent ankylosis may occur. (+info)
Slow tonic muscle fibers in the thyroarytenoid muscles of human vocal folds; a possible specialization for speech.
Most of the sounds of human speech are produced by vibration of the vocal folds, yet the biomechanics and control of these vibrations are poorly understood. In this study the muscle within the vocal fold, the thyroarytenoid muscle (TA), was examined for the presence and distribution of slow tonic muscle fibers (STF), a rare muscle fiber type with unique contraction properties. Nine human TAs were frozen and serially sectioned in the frontal plane. The presence and distribution pattern of STF in each TA were examined by immunofluorescence microscopy using the monoclonal antibodies (mAb) ALD-19 and ALD-58 which react with the slow tonic myosin heavy chain (MyHC) isoform. In addition, TA muscle samples from adjacent frozen sections were also examined for slow tonic MyHC isoform by electrophoretic immunoblotting. STF were detected in all nine TAs and the presence of slow tonic MyHC isoform was confirmed in the immunoblots. The STF were distributed predominantly in the medial aspect of the TA, a distinct muscle compartment called the vocalis which is the vibrating part of the vocal fold. STF do not contract with a twitch like most muscle fibers, instead, their contractions are prolonged, stable, precisely controlled, and fatigue resistant. The human voice is characterized by a stable sound with a wide frequency spectrum that can be precisely modulated and the STF may contribute to this ability. At present, the evidence suggests that STF are not presented in the vocal folds of other mammals (including other primates), therefore STF may be a unique human specialization for speech. (+info)
Osteoarthritis in cricoarytenoid joint.
OBJECTIVE: Occurrence of osteoarthritis is a frequent event of limb joints in people over 40 years of age. The human cricoarytenoid joint is comparable with the joints of the limbs despite its structure and extracellular matrix composition. To date, little is known about the occurrence of osteoarthritis in the human cricoarytenoid joint. METHODS: Sixty-eight cricoarytenoid joints (42 male and 26 female, age 25-98 years) were analysed by means of histology, lectin histochemistry, immunohistochemistry as well as scanning and transmission electron microscopy. RESULTS: About 50% of the investigated cricoarytenoid joints aged over 40 years show degenerative changes in their joint surface structure at varying levels of intensity. The articular cartilage surface is fibrillated in some places and sometimes shows fissures. A demascing of collagen fibrils next to the joint surface and a loss of proteoglycans in the upper cartilage layers can be observed. Chondrocytes near the joint surface appear as voluminous chondrocyte clusters. The clusters and the superficial cartilage layer show a positive reaction to type VI collagen antibodies. The distribution patterns of lectins are completely changed in fibrillated cartilage areas. CONCLUSION: Degenerative alterations in diarthrodial joints resembling osteoarthritis can occur in the joints of the larynx. These structural changes of the articular cartilage are comparable to osteoarthritis of the limb joints. Osteoarthritis in the cricoarytenoid joint may lead to impaired movements of the arytenoid cartilages. Functionally the structural changes may lead to negative consequences during vocal production, such as impaired vocal quality and reduced vocal intensity. (+info)
Active upper airway closure during induced central apneas in lambs is complete at the laryngeal level only.
We tested the hypotheses that active upper airway closure during induced central apneas in nonsedated lambs 1). is complete and occurs at the laryngeal level and 2). is not due to stimulation of the superior laryngeal nerves (SLN). Five newborn lambs were surgically instrumented to record thyroarytenoid (TA) muscle (glottal constrictor) electromyographic (EMG) activity with supra- and subglottal pressures. Hypocapnic and nonhypocapnic central apneas were induced before and after SLN sectioning in the five lambs. A total of 174 apneas were induced, 116 before and 58 after sectioning of the internal branch of the SLN (iSLN). Continuous TA EMG activity was observed in 88% of apneas before iSLN section and in 87% of apneas after iSLN section. A transglottal pressure different from zero was observed in all apneas with TA EMG activity, with a mean subglottal pressure of 4.3 +/- 0.8 cmH2O before and 4.7 +/- 0.7 cmH2O after iSLN section. Supraglottal pressure was consistently atmospheric. Sectioning of both iSLNs had no effects on the results. We conclude that upper airway closure during induced central apneas in lambs is active, complete, and occurs at the glottal level only. Consequently, a positive subglottal pressure is maintained throughout the apnea. Finally, this complete active glottal closure is independent from laryngeal afferent innervation. (+info)
Muscle fiber type composition and effects of vocal fold immobilization on the two compartments of the human posterior cricoarytenoid: a case study of four patients.
The human posterior cricoarytenoid (PCA) muscle is divided into two compartments, the vertical and horizontal bellies, which contain differences in their myosin heavy chain (MyHC) composition. Using immunohistochemical techniques on whole PCA samples, this study provides a more thorough description of the fiber type composition of entire bellies of the PCA. Four patients provided complete PCA samples containing both compartments of their right and left sides; two with unilaterally immobilized vocal folds. The horizontal belly had 80% slow (type I) fibers and 20% fast (type II) fibers. The vertical belly contained equal amounts of slow and fast fibers (approximately 55%:45%); clearly distinguishing between two compartments. Atrophy of muscle fibers and fiber type grouping were also present in both normal and affected subjects; providing no clear confirmation of the clinical findings of vocal fold immobilization. Further study of the PCA muscle from patients with unilaterally immobilized vocal folds is needed. (+info)
Staining of human thyroarytenoid muscle with myosin antibodies reveals some unique extrafusal fibers, but no muscle spindles.
This study describes the myosin composition of extrafusal and intrafusal muscle fibers found in the human thyroarytenoid (TA) and sternohyoid (control) muscles. We sought to determine the presence of muscle spindles in the TA muscle, and to identify unusual extrafusal fiber types, using the commonly accepted approach of tissue staining with myosin isoform specific antibodies. Extrafusal fibers are organized into motor units, which subsequently produce muscle movement, whereas intrafusal fibers compose muscle spindles, the primary stretch receptor that provides afferent (feed back) information to the nervous system for regulation of motor unit length and tonicity. Immunohistochemical identification of muscle spindles was confirmed in sternohyoid, but not in TA samples; however, some extrafusal fibers contained tonic myosin. These results indicate that human TA muscle functions similar to some mammalian extraocular muscle, performing unloaded (non-weight bearing) contractions without afferent information from native muscle spindles. (+info)
Abnormal movement of the arytenoid region as a cause of upper airway obstruction.
A 75 year old woman presented with a three week history of severe dyspnoea and cough. Auscultation and spirometry suggested extrathoracic inspiratory airway obstruction, and bronchoscopy showed abnormal motion of the arytenoid region (supraglottic area), causing upper airway obstruction only during forced inspiratory efforts. Sedatives improved the symptoms within a week. It is suggested that reversible malfunction of the arytenoid region can be responsible for upper airway obstruction. (+info)