Biomedical subjects

I Sanders

Publications and source records attributed to I Sanders.

At least 19 recordsLinked to original sources

PubMed2001

Neuromuscular compartments and fiber-type regionalization in the human inferior pharyngeal constrictor muscle.

The inferior pharyngeal constrictor (IPC) muscle functions during swallowing, respiration, and vocalization. The most-caudal portion of the IPC is believed to be part of the functional upper esophageal sphincter (UES). We hypothesized that the caudal fibers of the human IPC may have enzyme-histochemical characteristics similar to those of the cricopharyngeus muscle, a major component of the UES. In this study, human IPC muscles obtained from autopsy were studied using Sihler's stain to examine innervation patterns, and using myofibrillar ATPase, NADH tetrazolium reductase (NADH-TR), and succinic dehydrogenase (SDH) techniques to investigate the distribution and oxidative capacity of the slow- (type I) and fast- (type II) twitch fibers in the muscle. The results showed that the human IPC consists of at least two neuromuscular compartments (NMCs): rostral and caudal. Each of the NMCs was innervated by a separate nerve branch derived from the pharyngeal branch of the vagus nerve. The rostral NMC is faster (39% type I, 61% type II) than the caudal NMC (70% type I, 30% type II). In addition, two histochemically-delineated fiber layers were identified in the human IPC: a slow inner layer (SIL) with predominantly type I fibers (66%), and a fast outer layer (FOL) with predominantly type II fibers (62%) (P < 0.01). However, the dimensions of both fiber layers and proportions of the muscle fiber types varied with the NMCs. Specifically, the ratio of the thickness of the SIL to FOL was approximately 2:1 for the caudal NMC and approximately 1:2 for the rostral NMC, respectively. In the SIL the type I fibers accounted for 84% for the caudal NMC and 69% and 44% for the lower and upper portions of the rostral NMC. In contrast, the type II fibers in the FOL accounted for 46% for the caudal NMC and 67% and 74% for the lower and upper portions of the rostral NMC, respectively (P < 0.01). The caudal NMC of the IPC shared histochemical characteristics with the cricopharyngeus muscle, in that it contained predominantly slow oxidative fibers. Overall, the caudal NMC and the SIL in the IPC had high NADH-TR and SDH activities. However, different patterns of oxidative enzyme activity were identified in both type I and type II fibers. This study provided histochemical evidence for the concept that the caudal NMC within the IPC contributes to the functional UES. In addition, the two histochemically-defined fiber layers in the IPC may be a specialized adaptation in humans to enable different upper-airway functions during respiration, swallowing, and speech.

Deglutition↗

PubMed2001

Mapping of brain stem neuronal circuitry active during swallowing.

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 drawings of brain stem structures for different levels throughout the brain stem. Control animals underwent sham experiments. After subtraction of the areas of fos labeling seen in controls, all experimental rats showed fos-labeled neurons in very discrete and localized areas, including practically all regions implicated by prior neurophysiology studies of swallowing. The distribution of labeled neurons was more dispersed through the brain stem than current theories of swallowing would suggest. Specifically, recent studies of swallowing control have focused on the nucleus of the solitary tract (NST) and the region surrounding the nucleus ambiguus (periambigual area) just rostral to the obex. These areas contained fos-labeled neurons, but unexpectedly, heavy labeling was found in the same areas caudal to the obex. Areas containing the heaviest labeling were specific subnuclei of the NST and surrounding reticular formation; the periambigual area; and the intermediate reticular zone in the pons and caudal medulla. Interestingly, none of these anatomic structures had uniform fos labeling; this finding suggests that the unlabeled areas are involved in other oromotor behaviors, or that the specific protocol did not activate the full population of swallowing-related neurons. A notable finding of this study is a candidate for the central pattern generator (CPG) of swallowing. Careful lesioning studies in cats strongly suggest that a region in the rostral-medial medulla contains the CPG for swallowing, although the exact location of the CPG was never pinpointed. In the homologous region of the rat brain stem, fos labeling was only found in a small group of neurons within the gigantocellular reticular formation that may be a candidate for the CPG. In summary, correlation with prior physiology experiments suggests that this experiment appears to have delineated many, if not all, of the components of the swallowing circuit for the first time in any mammal. In addition, other areas were found that might also be swallowing-related. One notable example is a small group of fos-labeled cells that may be the CPG for swallowing. Further studies are required to clarify the specific roles of the fos-labeled neurons seen in this study.

Animals↗

PubMed2000

Neuromuscular specializations of the pharyngeal dilator muscles: II. Compartmentalization of the canine genioglossus muscle.

The genioglossus (GG) muscle is divided into horizontal and oblique compartments that are the main protrusor and depressor muscles of the tongue, respectively. In humans the GG plays an important role in speech articulation, swallowing, and inspiratory dilation of the pharynx. At present, little is known about the neuromuscular specializations of the GG in any mammal. This study examined the specializations of these compartments in the canine tongue using a variety of anatomical and histochemical techniques. Six canine GG muscles were sectioned and stained for myofibrillar ATPase to study muscle fiber types; five whole-mount GG muscles were stained for acetylcholinesterase (AChE) to study the distribution of motor endplates; and eight whole mount GG muscles were processed with Sihler's stain to study the entire nerve supply pattern. In addition, the arrangement of muscle fibers of the GG within the tongue was also determined (N = 3). The most notable difference between the compartments of the GG was their proportions of fast and slow twitch muscle fibers: the horizontal compartment contained 64% slow twitch muscle fibers compared to 41% in the oblique compartment. In addition, although the oblique compartment appeared to be grossly homogeneous, it could be divided into thirds by significant differences in the percentages of slow twitch fibers: posterior (23%), middle (15%), and anterior (56%; P < 0.05). The muscle fibers of the oblique GG within the tongue were found to be divided into medial and lateral layers that run vertically and transversely, respectively. The nerve supply to each third of the oblique GG formed a plexus with the anterior third being the densest. The innervation pattern of the oblique GG was also notable as terminal nerve branches coursing parallel to the muscle fascicles gave off perpendicular secondary branches along each motor endplate band. These secondary nerve branches connected the primary nerves and formed a regularly spaced grid throughout the compartment. Evidently, the two compartments of the GG exhibited different anatomical specializations. The horizontal had a slow muscle fiber profile and simple innervation pattern; these qualities are possibly related to its single force vector and respiratory related activity. The oblique compartment had a relatively fast muscle fiber profile with evidence for three separate functional subdivisions. The most anterior part was noticeably different, and was presumably specialized for fine motor control of the tip of the tongue. The vertically oriented fibers of the oblique GG within the tongue body may function as a midline depressor of the tongue, whereas its transversely oriented fibers could play a role in narrowing the tongue during other motor tasks.

Acetylcholinesterase↗

PubMed2000

Sensory nerve supply of the human oro- and laryngopharynx: a preliminary study.

To date, the details of human sensory innervation to the pharynx and upper airway have not been demonstrated. In this study, a single human oro- and laryngopharynx obtained from autopsy was processed with a whole-mount nerve staining technique, Sihler's stain, to determine its entire sensory nerve supply. The Sihler's stain rendered all mucosa and soft tissue translucent while counterstaining nerves. The stained specimen was then dissected and the nerves were traced from their origins to the terminal branches. It was found that the sensory innervation of the human pharynx is organized into discrete primary branches that innervate specific areas, although these areas are often connected by small neural anastomoses. The density of innervation varied, with some areas receiving almost no identifiable nerve supply (e.g., posterior wall of the hypopharynx) and certain areas contained much higher density of sensory nerves: the posterior tonsillar pillars; the laryngeal surface of the epiglottis; and the postcricoid and arytenoid regions. The posterior tonsillar pillar was innervated by a dense plexus formed by the pharyngeal branches of the IX and X nerves. The epiglottis was densely innervated by the internal superior laryngeal nerve (ISLN) and IX nerve. Finally, the arytenoid and postcricoid regions were innervated by the ISLN. The postcricoid region had higher density of innervation than the arytenoid area. The use of the Sihler's stain allowed the entire sensory nerve supply of the pharyngeal areas in a human to be demonstrated for the first time. The areas of dense sensory innervation are the same areas that are known to be the most sensitive for triggering reflex swallowing or glottic protection. The data would be useful for further understanding swallowing reflex and guiding sensory reinnervation of the pharynx to treat neurogenic dysphagia and aspiration disorders.

Aged↗

PubMed1999

Neuromuscular organization of the canine tongue.

The tongue manipulates food while chewing and swallowing, dilates the airway during inspiration, and shapes the sounds of speech in humans. While performing these functions the tongue morphs through many complex shapes. At present it is not known how the muscles of the tongue perform these complex shape changes. The difficulty in understanding tongue biomechanics is partly due to gaps in our knowledge regarding the complex neuromuscular anatomy of the tongue. In this study the motor and sensory nerve anatomy of four canine tongues was studied with Sihler's stain, a technique that renders most of the tongue tissue translucent while counterstaining nerves. An additional tongue specimen was serially sectioned to provide a reference for the muscle structure of the tongue. The hypoglossal nerve (XII) has approximately 50 primary nerve branches that innervate all intrinsic and extrinsic tongue muscles. Two extrinsic muscles, the styloglossus and hyoglossus, are innervated by about three to four branches from the lateral division of the XII. The third extrinsic muscle, the genioglossus, is composed of oblique and horizontal compartments, which receive about ten nerve branches from the medial division of the XII. The intrinsic muscles are composed of many neuromuscular compartments. On each side, the superior longitudinal muscle had an average of 40 distinct muscle fascicles that spanned the length of the tongue. Each of the fascicles is supplied by a nerve branch. The inferior longitudinal muscle had a similar organization. Each of the transverse and vertical muscles is composed of over 140 separate muscle sheets, and every sheet is innervated by a separate terminal nerve. The muscle sheets from the vertical and transverse alternate their orientation 90 degrees throughout the length of the tongue. It is concluded that the intrinsic canine tongue muscles are actually composed of groups of neuromuscular compartments that are arranged in parallel (longitudinal muscles) or in a precise alternating sequence (transverse and vertical muscles). This arrangement suggests that the compartments from the different tongue muscles could cooperate to control the three-dimensional contractile state of their local area. This hypothesis could explain how many different tongue shapes are formed, and is supported by physiologic evidence.

Animals↗

PubMed1999

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.

Adult↗

PubMed1999

Tracheal transplantation: defining the vascular territory of the canine cranial thyroid artery.

The management of long-segment tracheal stenosis remains an unsolved clinical problem that has significant implications for the survival of some patients and the quality of life of others. However, recent advances in microvascular tissue transfer may allow tracheal transplantation to be used as a treatment option. Studies in dogs have demonstrated that the reanastomosis of the cranial thyroid artery (CTA) after the transplantation of a short segment of trachea sustains cartilage viability. However, the distal perfusion zone of the CTA within the canine trachea has not been described. Hence it is unclear what length of trachea can be safely harvested, with use of the CTA as the donor artery, without risking ischemia of the distal trachea. This study determined the perfusion territory of the CTA by use of latex or dye infusion via the thyroid branches of the CTA. Findings in five perfusion-fixed cadaver mongrel dogs (8 to 12 kg) were studied. In each dog, both common carotid arteries were dissected and the CTAs identified. The right CTA was ligated and the left common carotid artery was ligated cranial to the CTA. The left common carotid artery was perfused for 10 minutes under 100 mm Hg pressure with black india ink/saline solution (20:1000 ml) or with blue latex solution. Perfusion territories were determined by grossly and microscopically measuring the region of stain in the endolaryngeal and endotracheal airways. The results demonstrated that up to 18 ipsilateral rings of the canine trachea are perfused after injection of dye under physiologic pressure into the CTA. Contralateral staining was also noted, but to a lesser degree. These results suggest that the canine CTA may perfuse, on average, a 16- to 17-ring tracheal segment.

Animals↗

PubMed1999

Interaction between the endophytic fungus Epichloe bromicola and the grass bromus erectus: effects of endophyte infection, fungal concentration and environment on grass growth and flowering

Epichloe bromicola is an endophytic fungal species that systemically and perennially colonizes intercellular spaces of leaf blades, leaf sheaths and culms of Bromus grass species. E. bromicola causes choke disease in B. erectus, suppressing maturation of most, if not all, host inflorescences. In an investigation of the interaction between fungus and host, we used a quantitative polymerase chain reaction technique to estimate the amount of fungal DNA, and thereby fungal concentration, in host plants. Fungal concentration was directly correlated with vegetative vigour of the plant, as measured by longest leaf length, number of tillers and vegetative above-ground biomass, suggesting that, during vegetative growth, the endophytic fungus is most beneficial for the plant when present in high concentrations. In contrast, the reproduction of the plant, as measured by the number of functional inflorescences, was inversely correlated with fungal concentration: the majority of infected plants, and all that were associated with high concentrations of fungi, were diseased. Thus, the benefit of endophyte infection for the plant is coupled with the disadvantages of infertility. Fungal concentration was shown to be at least in part genetically determined because fungal concentration differed significantly in different plant-endophyte genotype combinations (symbiotum). In a field experiment with normal and CO2-enriched environments, elevated CO2 levels favoured fungal reproductive vigour over host reproductive vigour, suggesting that these plant endophytes would be at a selective advantage in a corresponding environmental-change scenario. We conclude that a dynamic and complex relationship between fungal endophyte infection, fungal concentration, genotype and environment affects growth and fecundity of B. erectus and should contribute to the evolution of these plant-fungal interactions.

Journal Article↗

PubMed1999

Evaluation and management of bilateral vocal cord immobility.

Bilateral vocal cord immobility can be life threatening for some patients. Others, who have an open glottic chink, may have a breathy dysphonia, intermittent dyspnea, and stridor. These signs and symptoms may also be found in a number of other conditions that cause weakness or paradoxical motion of the vocal cords that mimics paralysis. These other conditions include central nervous system diseases, neuromuscular disorders, laryngospasm, and psychogenic disorders. In addition, patients with cricoarytenoid joint immobility or interarytenoid scar can also have similar symptoms at presentation. It is critical to consider the differential diagnosis of an assumed bilateral vocal cord paralysis and understand the management of paradoxical movement, weakness, joint fixation, interarytenoid scar, laryngospasm, and psychogenic disorders. The treatment for bilateral immobility should proceed only after a thorough evaluation, which might include electromyography and/or examination during general anesthesia under dense anesthetic paralysis. Reconstructive procedures are the treatments of choice, and destructive procedures should be chosen only as a last resort.

Arytenoid Cartilage↗

PubMed1998

Neuromuscular specializations of the pharyngeal dilator muscles: I. Compartments of the canine geniohyoid muscle.

BACKGROUND: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.

Acetylcholinesterase↗

PubMed1998

Anatomy of the human internal superior laryngeal nerve.

The mucosa of the larynx contains one of the most dense concentrations of sensory receptors in the human body. This sensitivity is used for reflexes that protect the lungs, and even momentary loss of this function is followed rapidly by life-threatening pneumonia. The internal superior laryngeal nerve (ISLN) supplies the innervation to this area, and, to date, the distribution and branching pattern of this nerve is unknown. Five adult human larynges were processed by using Sihler's stain, a technique that clears soft tissue while counterstaining nerves. The whole-mount specimens were then dissected to demonstrate the branching of the ISLN from its main trunk down to the level of terminal axons. The human ISLN is divided into three divisions: The superior division supplies mainly the mucosa of the laryngeal surface of the epiglottis; the middle division supplies the mucosa of the true and false vocal folds and the aryepiglottic fold; and the inferior division supplies the mucosa of the arytenoid region, subglottis, anterior wall of the hypopharynx, and upper esophageal sphincter. Several dense sensory plexi that cross the midline were seen on the laryngeal surface of the epiglottis and arytenoid region. The human ISLN also appears to supply motor innervation to the interarytenoid (IA) muscle. A detailed map is presented of the distribution of the ISLN within the human larynx. The areas seen to receive the greatest innervation are the same areas that have been shown by physiological experiments to be the most sensate: the laryngeal surface of the epiglottis, the false and true vocal folds, and the arytenoid region. The observation that the human ISLN appears to supply motor innervation to the IA muscle is contrary to current concepts of the ISLN as a purely sensory nerve. These findings are relevant to understanding how the laryngeal protective reflexes work during activities like swallowing. The nerve maps can be used to guide surgical attempts to reinnervate the laryngeal mucosa when sensation is lost due to neurological disease.

Humans↗

PubMed1998

Muscle spindles are concentrated in the superior vocalis subcompartment of the human thyroarytenoid muscle.

It is hypothesized that different parts of the thyroarytenoid muscle (TA) are functionally specialized. Specifically, the TA is divided into a lateral muscularis compartment and a medial vocalis compartment. This study examined the distribution of muscle spindles throughout the human TA as an indicator of these functional differences. Histological cross-sections from the anterior, middle, and posterior regions of five human membranous vocal folds were examined for the number and location of muscle spindles. There was an average of 6.1 muscle spindles in sections from each region with no significant variation between the different regions (p < .05). However, in sections from all three regions, the muscle spindles were always found to be concentrated in the superior medial quadrant of the TA (mean 85.9%, p < .01). The inferior medial, superior lateral, and inferior lateral quadrants of the TA contained 11.96%, 2.17%, and 0%, respectively, of the total muscle spindles. Within the superior medial quadrant, most of the muscle spindles were localized in the most superficial part of the muscle. The results of this study demonstrate that the majority of TA muscle spindles are concentrated in its superior medial quadrant, an area we have termed the superior vocalis subcompartment (SC). This finding suggests that the superior vocalis SC is functionally distinct from the remainder of the TA. It is hypothesized that tension in the superior vocalis SC can be controlled independently from the remainder of the TA, and this capability is used to effect the biomechanics of vocal fold vibration during phonation.

Humans↗

PubMed1998

Innervation pattern of the temporalis muscle.

The purpose of this article is to describe the neural anatomy of the temporalis muscle as dissected along the intramuscular temporal fascial plane. This sagittal plane is a natural cleavage plane of the muscle, which is explored along with its relationship to the deep temporal nerve. Eight temporalis muscle specimens were removed in their entirety from 8 preserved cadavers. The muscles were selected based on whether they were grossly intact prior to procurement for processing. The muscle specimens were then processed over a 3-month period using Sihler's staining technique. Muscle dissection was performed along the intramuscular fascial plane under an operating microscope, taking care to preserve the underlying nerve and arterial anatomy. Dissections demonstrated an anterior and posterior division of the deep temporal nerve running within the deep portion of the muscle below the intramuscular fascial plane. This fascial layer provided a natural dissection plane to expose and evaluate the underlying nerve and arterial anatomy. In all specimens the deep temporal artery originated with the anterior temporal nerve and then branched into an anterior and posterior division. The innervation density and nerve caliber of the anterior portion of the muscle was much greater than that of the posterior, correlating with a greater anterior muscle bulk. This may have implications in differences in fiber type and functional regionalization of the muscle. The results of this anatomic study support the finding of an anterior and posterior division of the deep temporal nerve within the deep portion of the temporalis muscle. In addition, differences in the innervation density and muscle bulk lend credence to the possibility of regional muscle specialization. The natural cleavage plane of the intramuscular temporal fascia may have clinical ramifications for temporalis myofascial flaps while preserving the underlying neural anatomy to allow for normal residual temporalis muscle function.

Dissection↗

PubMed1998

Neuromuscular organization of the human upper esophageal sphincter.

The upper esophageal sphincter (UES) is a key component of swallowing, and yet, its anatomy and function are still incompletely understood. The UES is a functional entity that is composed of three muscles: the cricopharyngeal (CP) muscle, the inferior pharyngeal constrictor (IPC) muscle, and the upper esophageal (UE) muscle. This study compared the anatomy of the three muscles of the UES in nine human autopsy specimens. The variables examined included the pattern of motor end plates (acetylcholinesterase stain), the proportion of fast- and slow-twitch muscle fibers (myofibrillar adenosinetriphosphatase), and the details of their nerve supply (Sihler's stain). The results demonstrated that each variable is different in the three muscles. For example, the IPC muscle is innervated by the pharyngeal plexus, the CP muscle by both the pharyngeal plexus and the recurrent laryngeal nerve (RLN), and the UE muscle by the RLN. The IPC and CP muscles showed distinct motor end plate bands, while the horizontal part of the CP muscle also contained small and randomly scattered end plates. This latter pattern was present throughout the UE muscle. Analysis of the muscle fiber types of the UES revealed a type I (slow) predominance (89%) in the CP and UE muscles and a type II (fast) predominance (62%) in the IPC muscle. However, the IPC muscle is composed of two layers: a fast, thick, outer layer (90% type II) and a slow, thin, inner layer (85% type I). The implications of these findings for the diagnosis and treatment of UES dysfunction will be discussed.

Deglutition↗

PubMed1998

Human vocalis contains distinct superior and inferior subcompartments: possible candidates for the two masses of vocal fold vibration.

It is not understood how different parts of the thyroarytenoid muscle contribute to vocal fold vibration. This study investigated the medial part of the thyroarytenoid muscle, the vocalis compartment, for anatomic differences that might suggest functionally distinct areas. Twenty human vocal folds were frontally sectioned and stained with hematoxylin and eosin. A single section from the middle of each vocal fold was magnified, and the muscle fascicles of the most superficial 25% of the vocalis compartment were then examined. In all 20 specimens the vocalis compartment could be separated into 2 plainly distinct subcompartments: the inferior vocalis compartment was composed of a single large muscle fascicle that contained densely packed muscle fibers of similar size; the superior vocalis compartment was composed of multiple small fascicles in which the muscle fibers were loosely arranged and varied greatly in size. On average, the inferior vocalis subcompartment composed 60% of the medial surface of the thyroarytenoid muscle. The superior subcompartment composed the remaining 40% of the medial surface, but also continued past the vocal ligament to make up the superior surface of the thyroarytenoid muscle. It is concluded that 2 distinct entities make up the vocalis compartment of the thyroarytenoid muscle. Their anatomy is so markedly different it suggests that they may function independently. One possibility is that they reflect the 2 masses observed in the superior and inferior aspects of the vocal fold during vibration.

Humans↗

PubMed1998

Botulinum toxin decreases salivation from canine submandibular glands.

The objective of this study was to determine whether botulinum toxin types A and D reduced the production of saliva from the submandibular glands of 18 dogs. The left submandibular glands of 8 dogs were injected with increasing doses of botulinum type A toxin (range 10 to 70 units), and the left glands of 10 dogs were injected with botulinum type D toxin (50 or 100 units). The right gland of each dog was injected with equivalent volumes of saline solution to serve as control. Six days after the injection, the lingual nerve was electrically stimulated for 10 minutes (3 mAmp, 20 Hz). The resulting volume of saliva was collected and weighed. Overall, the glands injected with types A or D toxin produced significantly less saliva than comparable glands injected with saline solution. Six of 8 dogs injected with type A toxin showed a significant decrease in saliva production (range 10.1% to 19.2%, one-sided p value = 0.0375) when compared with the controls. Nine of 10 dogs injected with type D toxin demonstrated a highly significant reduction in saliva production (total average decrease = 60%, two-sided pvalue = 0.001) when compared with the controls. We concluded that intraglandular injections of botulinum toxin types A and D significantly reduced the production of saliva from canine submandibular glands. The potential applications of intraglandular injections of botulinum toxin are discussed.

Animals↗

PubMed1996

The innervation of the human upper esophageal sphincter.

The neuroanatomy and physiology of the human upper esophageal sphincter (UES) has long been controversial. As a result, there has been little progress in diagnosing and treating dysphagias involving this area. In this study, three specimens of the UES obtained from human autopsies were examined by Sihler's stain. This stain clears soft tissue while counterstaining the nerves, thereby allowing nerve supply to each muscle of the UES to be demonstrated. It was found that the nerve supply to each component of the UES is substantially different. The inferior pharyngeal constrictor (IPC) is supplied by a dense linear plexus which is about 1.0-1.5 cm wide and 10 cm long and located about 1.5 cm lateral to the attachment of the IPC on the thyroid lamina. The cricopharyngeal (CP) muscle receives its innervation from below via the recurrent laryngeal nerve (RLN) and from above via the pharyngeal plexus. Neural connections between the RLN and the pharyngeal plexus were observed. Finally, the upper esophagus (UE) is innervated by the RLN. The innervation pattern of each component of the UES suggests functional differences between these muscles. These observations help clarify the innervation of the UES. Accurate knowledge of the neuroanatomy of the UES is necessary for advances in diagnosis and treatment of pharyngeal dysphagia.

Culture Techniques↗

PubMed1995

Axons enter the human posterior cricoarytenoid muscle from the superior direction.

OBJECTIVE: To examine the possibility that axons from the superior laryngeal nerve travel inferiorly through connections between the recurrent and the superior laryngeal nerves within the interarytenoid muscle to innervate intrinsic laryngeal muscles. MATERIALS: The branch point from the recurrent laryngeal nerve to the posterior cricoarytenoid muscle was excised from five human larynges. METHODS: The section of nerve was first microdissected to remove the epineurium. Then, the specimen was incubated at 37 degrees C in a 1% collagenase solution, which was alternated with 0.4% chymopapain or 0.25% trypsin. Finally, the specimen was stained with 1% toluidine blue. RESULTS: In all five specimens, axons could be seen entering the nerve branch to the posterior cricoarytenoid muscle from the superior direction. In one specimen, about one third of the axons entering the muscle could be identified as arising from the superior direction. In two cases, the superior axons could be traced back to the recurrent laryngeal nerve branch to the interarytenoid muscle. CONCLUSIONS: These results suggest that axons from the superior laryngeal nerve connect with the recurrent laryngeal nerve in the area of the interarytenoid muscle. Furthermore, these axons travel inferiorly to innervate the posterior cricoarytenoid muscle.

Adult↗