The paired posterior cricoarytenoid (PCA) muscle has three separate muscle bellies that differ in... more The paired posterior cricoarytenoid (PCA) muscle has three separate muscle bellies that differ in muscle fiber type (percentage of fast vs. slow twitch) and electromyelographic activity, and, in addition, produce different movements of the arytenoids when stimulated. An investigation of the innervation of the muscle was undertaken to demonstrate the existence of separate functional units. The intramuscular nerve supply of the PCA from five sacrificed dogs were microdissected. The intramuscular nerves of three additional dogs were removed and stained for acetylcholinesterase, which differentiates axons bound for fast- and slow-twitch muscle, and sensory end organs. Three separate fascicles are described entering the PCA muscle from a single branch of the recurrent laryngeal nerve. The three fascicles differ in axon type composition and in sensory, autonomic, and motor percentages, with the ratio of fast twitch to slow twitch varying from 0.78 to 1.5 to 1.7 (P less than .05). This variation supports separate functional capabilities for the three muscle bellies of the PCA.
Annals of Otology, Rhinology, and Laryngology, Sep 1, 2003
There are currently no descriptions of neonatal tongue anatomy. Therefore, there have been no rep... more There are currently no descriptions of neonatal tongue anatomy. Therefore, there have been no reports on the morphological differences between it and the adult tongue that would suggest its suitability for suckling. Serial coronal sections of a neonatal tongue were used to create a 3-dimensional model that was compared to that of the adult tongue. Compared to the adult human tongue, the neonatal tongue was found to contain 1) considerably less fat and soft tissue; 2) a thinner mucosa; 3) relatively enlarged extrinsic musculature; 4) a less-developed superior longitudinal muscle, resulting in a flat dorsal surface; and 5) attachments between the extrinsic muscles and the transverse muscle group that have not been identified in the adult tongue. The particular structure of the neonatal tongue suggests how the neonatal tongue is specialized for suckling.
Otolaryngologic Clinics of North America, Oct 1, 1991
Most functional electrical stimulation (FES) research has focused on the spinal cord-injured pati... more Most functional electrical stimulation (FES) research has focused on the spinal cord-injured patient whose muscles are paralyzed but still maintain their innervation. This article details the investigation of FES of the laryngeal muscles. In time, FES may become a useful treatment for bilateral vocal cord paralysis (BVCP) and for some laryngeal movement disorders.
Little is known about the structure and innervation of the geniohyoid muscle (GH), which is an im... more Little is known about the structure and innervation of the geniohyoid muscle (GH), which is an important pharyngeal dilator muscle activated in swallowing and respiration. The neuromuscular specializations of the canine GH were studied in detail by using a combination of histological, histochemical, and anatomical techniques. First, hematoxylin and eosin staining, Gomori's rapid one-step trichrome stain, and silver impregnation were used to determine the terminations of muscle fibers and existence of fibrous septa within the muscle (n = 8). Second, myofibrillar ATPase staining was employed to document the muscle fiber type distribution (n = 8). Finally, Sihler's stain (n = 10) and wholemount acetylcholinesterase staining (n = 8) were used to examine the distribution of the nerve supply within the muscle. The canine GH is divided into rostral and caudal compartments, which are arranged in series and separated by a transverse fibrous septum. Each compartment receives its own primary nerve branch, which supplies a separate motor endplate zone. The rostral compartment is innervated bilaterally, whereas the caudal compartment is innervated ipsilaterally. The rostral compartment was composed of significantly more type I (slow twitch) muscle fibers (56%) than the caudal compartment (25%). The canine GH is composed of two in-series neuromuscular compartments rather than a single muscle as traditionally believed. This anatomical finding suggests that these two compartments may function independently under different physiological conditions.
Most of the sounds of human speech are produced by vibration of the vocal folds, yet the biomecha... more 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.
Slow tonic muscle fibers (ST) are common in reptiles and amphibians, but except for their similar... more Slow tonic muscle fibers (ST) are common in reptiles and amphibians, but except for their similarity to the intrafusal muscle fibers of muscle spindles, they are quite rare in mammals. Their morphology and physiology are unusual in many ways. They have multiple en ...
The purpose of this study is twofold. First, to introduce a new phenomenon--abductor vocal cord s... more The purpose of this study is twofold. First, to introduce a new phenomenon--abductor vocal cord spasm, or abductor laryngospasm. Second, to reconcile a longstanding discrepancy involving the effect of lung inflation on vocal cord position. Abductor laryngospasm was induced in six anesthetized, tracheotomized dogs by the administration of continuous positive airway pressure (CPAP) after occlusion of the trachea for 60 seconds. Abductor laryngospasm was characterized by sustained vocal cord abduction with concomitant massive, continuous posterior cricoarytenoid muscle (PCA) electromyography (EMG) activity and little or no laryngeal adductor muscle EMG activity. Vocal cord opening was sustained for up to 90 seconds. In the same dogs, administration of CPAP, after hyperventilation of the animal, resulted in adductor laryngospasm. Adductor laryngospasm was characterized by steady apposition of the vocal cords, massive laryngeal adductor muscle EMG activity, and silent PCA EMG activity. Abductor laryngospasm appears to be the physiologic converse of adductor laryngospasm. The results of this study show that lung inflation can produce either vocal cord abduction or adduction, depending on whether the dog is hypoventilated or hyperventilated before administration of CPAP.
The intent of this study was to demonstrate that the technique of transmucosal electrical stimula... more The intent of this study was to demonstrate that the technique of transmucosal electrical stimulation of laryngeal muscles may be of clinical use in airway management. Specifically, its ability to overcome laryngospasm was evaluated. Laryngospasm was induced in eight tracheotomized dogs by hyperventilating each dog, and then applying 0.1 M ammonia to the laryngeal mucosa while administering continuous positive airway pressure (CPAP). Laryngospasm was defined by steady apposition of the vocal cords, massive electromyographic activity in the laryngeal adductor muscles, absence of such activity in the posterior cricoarytenoid muscle (PCA), and intraglottic pressure greater than 80 mm Hg. Upon transmucosal application of 10 mAmp current to the PCA bilaterally, the vocal cords abducted for the duration of the stimulus. We theorize that overcoming laryngospasm by electrostimulation involves a reflexive inhibition of the laryngeal adductors. This study provides an objective model for laryngospasm, and demonstrates that electrical manipulation of the vocal cords may have clinical relevance.
The Annals of otology, rhinology, and laryngology, 2001
A poorly understood neural circuit in the brain stem controls swallowing. This experiment studied... more A poorly understood neural circuit in the brain stem controls swallowing. This experiment studied the swallowing circuit in the rat brain stem by means of fos immunocytochemistry. The fos protein is a marker of activated neurons, and under experimental conditions, repetition of a behavior causes the fos protein to be produced in the neurons involved in that behavior. The fos technique has been successfully used to delineate neural circuits involved in reflex glottic closure, cough, and vocalization; however, the technique has not been used to map the swallowing circuit. Nine rats were used in this study. Swallows were evoked in anesthetized rats for 1 hour, then, after a 4-hour delay to allow maximum fos production, the rats were painlessly sacrificed by perfusion. The brain stems were removed and sectioned in the frontal plane, and every fourth section was immunoreacted for fos protein. All sections were examined by light microscopy, and cells positive for fos were marked on drawin...
The paired posterior cricoarytenoid (PCA) muscle has three separate muscle bellies that differ in... more The paired posterior cricoarytenoid (PCA) muscle has three separate muscle bellies that differ in muscle fiber type (percentage of fast vs. slow twitch) and electromyelographic activity, and, in addition, produce different movements of the arytenoids when stimulated. An investigation of the innervation of the muscle was undertaken to demonstrate the existence of separate functional units. The intramuscular nerve supply of the PCA from five sacrificed dogs were microdissected. The intramuscular nerves of three additional dogs were removed and stained for acetylcholinesterase, which differentiates axons bound for fast- and slow-twitch muscle, and sensory end organs. Three separate fascicles are described entering the PCA muscle from a single branch of the recurrent laryngeal nerve. The three fascicles differ in axon type composition and in sensory, autonomic, and motor percentages, with the ratio of fast twitch to slow twitch varying from 0.78 to 1.5 to 1.7 (P less than .05). This variation supports separate functional capabilities for the three muscle bellies of the PCA.
Annals of Otology, Rhinology, and Laryngology, Sep 1, 2003
There are currently no descriptions of neonatal tongue anatomy. Therefore, there have been no rep... more There are currently no descriptions of neonatal tongue anatomy. Therefore, there have been no reports on the morphological differences between it and the adult tongue that would suggest its suitability for suckling. Serial coronal sections of a neonatal tongue were used to create a 3-dimensional model that was compared to that of the adult tongue. Compared to the adult human tongue, the neonatal tongue was found to contain 1) considerably less fat and soft tissue; 2) a thinner mucosa; 3) relatively enlarged extrinsic musculature; 4) a less-developed superior longitudinal muscle, resulting in a flat dorsal surface; and 5) attachments between the extrinsic muscles and the transverse muscle group that have not been identified in the adult tongue. The particular structure of the neonatal tongue suggests how the neonatal tongue is specialized for suckling.
Otolaryngologic Clinics of North America, Oct 1, 1991
Most functional electrical stimulation (FES) research has focused on the spinal cord-injured pati... more Most functional electrical stimulation (FES) research has focused on the spinal cord-injured patient whose muscles are paralyzed but still maintain their innervation. This article details the investigation of FES of the laryngeal muscles. In time, FES may become a useful treatment for bilateral vocal cord paralysis (BVCP) and for some laryngeal movement disorders.
Little is known about the structure and innervation of the geniohyoid muscle (GH), which is an im... more Little is known about the structure and innervation of the geniohyoid muscle (GH), which is an important pharyngeal dilator muscle activated in swallowing and respiration. The neuromuscular specializations of the canine GH were studied in detail by using a combination of histological, histochemical, and anatomical techniques. First, hematoxylin and eosin staining, Gomori's rapid one-step trichrome stain, and silver impregnation were used to determine the terminations of muscle fibers and existence of fibrous septa within the muscle (n = 8). Second, myofibrillar ATPase staining was employed to document the muscle fiber type distribution (n = 8). Finally, Sihler's stain (n = 10) and wholemount acetylcholinesterase staining (n = 8) were used to examine the distribution of the nerve supply within the muscle. The canine GH is divided into rostral and caudal compartments, which are arranged in series and separated by a transverse fibrous septum. Each compartment receives its own primary nerve branch, which supplies a separate motor endplate zone. The rostral compartment is innervated bilaterally, whereas the caudal compartment is innervated ipsilaterally. The rostral compartment was composed of significantly more type I (slow twitch) muscle fibers (56%) than the caudal compartment (25%). The canine GH is composed of two in-series neuromuscular compartments rather than a single muscle as traditionally believed. This anatomical finding suggests that these two compartments may function independently under different physiological conditions.
Most of the sounds of human speech are produced by vibration of the vocal folds, yet the biomecha... more 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.
Slow tonic muscle fibers (ST) are common in reptiles and amphibians, but except for their similar... more Slow tonic muscle fibers (ST) are common in reptiles and amphibians, but except for their similarity to the intrafusal muscle fibers of muscle spindles, they are quite rare in mammals. Their morphology and physiology are unusual in many ways. They have multiple en ...
The purpose of this study is twofold. First, to introduce a new phenomenon--abductor vocal cord s... more The purpose of this study is twofold. First, to introduce a new phenomenon--abductor vocal cord spasm, or abductor laryngospasm. Second, to reconcile a longstanding discrepancy involving the effect of lung inflation on vocal cord position. Abductor laryngospasm was induced in six anesthetized, tracheotomized dogs by the administration of continuous positive airway pressure (CPAP) after occlusion of the trachea for 60 seconds. Abductor laryngospasm was characterized by sustained vocal cord abduction with concomitant massive, continuous posterior cricoarytenoid muscle (PCA) electromyography (EMG) activity and little or no laryngeal adductor muscle EMG activity. Vocal cord opening was sustained for up to 90 seconds. In the same dogs, administration of CPAP, after hyperventilation of the animal, resulted in adductor laryngospasm. Adductor laryngospasm was characterized by steady apposition of the vocal cords, massive laryngeal adductor muscle EMG activity, and silent PCA EMG activity. Abductor laryngospasm appears to be the physiologic converse of adductor laryngospasm. The results of this study show that lung inflation can produce either vocal cord abduction or adduction, depending on whether the dog is hypoventilated or hyperventilated before administration of CPAP.
The intent of this study was to demonstrate that the technique of transmucosal electrical stimula... more The intent of this study was to demonstrate that the technique of transmucosal electrical stimulation of laryngeal muscles may be of clinical use in airway management. Specifically, its ability to overcome laryngospasm was evaluated. Laryngospasm was induced in eight tracheotomized dogs by hyperventilating each dog, and then applying 0.1 M ammonia to the laryngeal mucosa while administering continuous positive airway pressure (CPAP). Laryngospasm was defined by steady apposition of the vocal cords, massive electromyographic activity in the laryngeal adductor muscles, absence of such activity in the posterior cricoarytenoid muscle (PCA), and intraglottic pressure greater than 80 mm Hg. Upon transmucosal application of 10 mAmp current to the PCA bilaterally, the vocal cords abducted for the duration of the stimulus. We theorize that overcoming laryngospasm by electrostimulation involves a reflexive inhibition of the laryngeal adductors. This study provides an objective model for laryngospasm, and demonstrates that electrical manipulation of the vocal cords may have clinical relevance.
The Annals of otology, rhinology, and laryngology, 2001
A poorly understood neural circuit in the brain stem controls swallowing. This experiment studied... more A poorly understood neural circuit in the brain stem controls swallowing. This experiment studied the swallowing circuit in the rat brain stem by means of fos immunocytochemistry. The fos protein is a marker of activated neurons, and under experimental conditions, repetition of a behavior causes the fos protein to be produced in the neurons involved in that behavior. The fos technique has been successfully used to delineate neural circuits involved in reflex glottic closure, cough, and vocalization; however, the technique has not been used to map the swallowing circuit. Nine rats were used in this study. Swallows were evoked in anesthetized rats for 1 hour, then, after a 4-hour delay to allow maximum fos production, the rats were painlessly sacrificed by perfusion. The brain stems were removed and sectioned in the frontal plane, and every fourth section was immunoreacted for fos protein. All sections were examined by light microscopy, and cells positive for fos were marked on drawin...
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