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At least 19 recordsLinked to original sources
PubMed2002

Do the tensor tympani and tensor veli palatini muscles of man form a functional unit? A histochemical investigation of their putative connections.

The discussion among anatomists and otolaryngologists about the muscles originating from the Eustachian tube and the connections between the tensor tympani and tensor veli palatini muscles started in the 1860s. From then on, a considerable number of contradictory hypotheses and data have been presented. However, before discussing whether or not these two muscles form a functional unit, interest should focus on the question of whether it is even possible. The cartilaginous portion of the Eustachian tube with all muscles originating from it, including the whole tensor tympani muscle, was dissected from five perfusion-fixed cadavers and removed in toto. Complete longitudinal serial sections of 10 microm were made in the axis of the tensor tympani muscle. Sections were alternatingly stained according to Cason's and Maskar's techniques. The macroscopic aspect (under the operating microscope) of a tendinous connection between the two muscles under consideration could be proven by the histochemical methods used in all cases. Based on our findings and the literature reviewed we are convinced that the tensor tympani and tensor veli palatini muscles of man constitute a functional unit. This represents an important step forward towards the understanding of the possible functions the tensor tympani muscle serve in man.

Eustachian Tube↗
PubMed1978

Electromyographic correlation of tensor tympani and tensor veli palatini muscles in man.

It is the purpose of this study to attempt a correlation of function, by electromyographic means, of the tensor tympani and tensor veli palatini muscles in humans. Despite the small number of patients tested, it is believed that the similarities and characteristics of the two are unmistakably equivalent. A separate theory for the combined tensor function is discussed in distinction to the stapedius mediated acoustic reflex. The concept of a single tensor muscle, with two anatomic divisions, a common nerve supply, and parallel function, is therefore submitted.

Ear, Middle↗
PubMed1983

Identification of motoneurons innervating the tensor tympani and tensor veli palatini muscles in the cat.

The somatotopic arrangement of the motoneurons associated with the two non-masticatory muscles innervated by the trigeminal motor nerve, tensor tympani (TT) and tensor veli palatini (TVP), was determined in the cat using retrograde transport of horseradish peroxidase. The motoneurons of the TT are distinct and separate, ventral and ventral-lateral to the rostral two-thirds of the trigeminal motor nucleus. The cells are smaller than those of the motor nucleus and constitute a parvocellular division. Based on functional and morphological criteria, TT motoneurons may be considered as an accessory trigeminal nucleus. The somatotopic arrangement of TVP motoneurons has been described for the first time. These motoneurons are located in the rostral two-thirds of the ventromedial division of the cat trigeminal motor nucleus. The location of motoneurons associated with TT and TVP does not fit the parcellation of the cat trigeminal motor nucleus as described by previous investigators. The motoneurons of these muscles can now be assigned to areas either within (TVP) or adjacent to (TT) the rostral two-thirds of the motor nucleus.

Animals↗
PubMedDate not supplied

The tensor tympani, stapedius, and tensor veli palatini muscles--an electromyographic study.

Electromyographic recordings of the activity of the tensor veli palatini, tensor tympani, and stapedius muscles were obtained from several adult human subjects. Muscle responses were recorded under four stimulus conditions, ie, contralateral intense wide-band noise, air jet to the eye, swallow, and electrical stimulation of the tongue. The results indicated that the two tensor muscles responded to the same stimuli in similar patterns. The latter muscle differed from the response of the stapedius.

Acoustic Stimulation↗
PubMedDate not supplied

Tensor tympani, a 'tuner' of tensor palati muscle.

The author has proved experimentally (in two dogs) that there is reflex hypertonia of the tensor palati muscle, synchronous with the 'shortening' reaction of the tensor tympani muscle in response to its "static" relaxation during the gradual passive inward displacement of the drum resulting from the negative intratympanic 'dip' due to absorption of air imprisoned within the middle ear. The author coined the term 'tuning' for the reflex hypertonia of tensor palati which is directly proportional to the degree of the slackness of its 'tuner', the muscle-tensor tympani. The degree of opening of the eustachian tube on swallowing depends upon the degree of 'tuning' of the tensor palati. The 'untuned' tensor palati fails to open the eustachian tube during swallowing. Presumably the excitation of tympanic chemoreceptors (glomus body) by the excess of CO2 during hypoxia of the tympanic cleft strengthens the 'shortening' reaction as well as the excitability of the tensor tympani muscle.

Animals↗
PubMed1985

An intracellular HRP-study of cat tensor tympani motoneurons.

The morphology of single tensor tympani motoneurons was investigated following antidromic identification and intracellular injection of horseradish peroxidase. Eight motoneurons were selected for complete reconstruction and quantitative analysis. The mean size of tensor tympani somata (26.3 +/- 1.8 micron) make this parvocellular cluster of motoneurons below the trigeminal motor nucleus a population of the smallest cranial motoneurons yet described. Axons emerged from either the soma or a primary dendrite. They coursed dorsolaterally frequently through the trigeminal motor nucleus before looping ventrolaterally into the Vth nerve. No collaterals were observed within the brainstem. The 5 primary dendrites of each cell branched heavily and, on average, exhibited 40 terminal branches with an average tree expansion of 1262.5 micron. The dendritic arborization extended far beyond the nuclear boundaries described by the distribution of cell bodies. These data suggest that the overall membrane area for synaptic innervation is large and thus it provides morphological evidence for the hypothesis that tensor tympani motoneurons receive divergent multisensory synaptic input. The latter assumption was supported by morphological and electrophysiological evidence including close the proximity of motoneuronal dendrites to auditory (superior olivary complex) and somatosensory (trigeminal) relay centers. Since no dendrite ever entered the trigeminal motor nucleus proper the tensor motoneuron pool is distinct from the trigeminal not only in terms of soma size, location and function, but also the disposition and expansion of the postsynaptic receptive field. Based on these criteria the tensor tympani motoneuron pool should no longer be regarded as an accessory trigeminal nucleus but be recognized in its own right as the tensor tympani motor nucleus of V.

Animals↗
PubMedDate not supplied

Role of the tensor tympani muscle in eustachian tube function.

In order to determine the role of the tensor tympani muscle in Eustachian tube function, pressure changes in the external and middle ear of 13 cats were measured under four experimental conditions. It was revealed that contraction of the tensor tympani muscle during swallowing did not result in any tympanic pressure rise which might assist in tubal ventilation. Acoustic stimulation was then used to measure consistent contraction of the tensor tympani muscle. Combined contraction of the tensor veli palatini and tensor tympani muscle under the condition of positive tympanic pressure failed to open the tube. It was concluded that the tensor tympani muscle might not play any part in tubal function.

Acoustic Stimulation↗
PubMed1987

A specialized innervation of the tensor tympani muscle in Macaca fascicularis.

The innervation of the tensor tympani muscle of the middle ear in Macaca fascicularis (cynomolgus monkey) was studied using the horseradish peroxidase (HRP) neural tracing technique. A compact column of small trigeminal motoneurons was labeled ipsilaterally following intramuscular application of HRP to the tensor tympani muscle. This column is located ventral and lateral to the dorsolateral division of the trigeminal motor nucleus, and just medial to the descending trigeminal nerve rootlets. No labeled neurons were present in the trigeminal mesencephalic nucleus or any other brainstem nucleus. Results are compared with those previously reported in several non-primate mammalian species, and in detail with that of the cat. A possible differential role of the tensor tympani muscle in acoustic modulation/middle ear aeration between primate and non-primate mammals is discussed.

Acetylcholinesterase↗
PubMedDate not supplied

Histochemical characteristics of the tensor tympani muscle in relation to the medial gastrocnemius muscle of the cat.

Serial 10-micron cryostat cross-sections of the tensor tympani muscle and of the medial gastrocnemius muscle from adult domestic cats were incubated for myofibrillar ATPase, NADH tetrazolium reductase (NADH-TR), succinic dehydrogenase (SDH), malate dehydrogenase (MDH) and menadione-linked alpha-glycerophosphate dehydrogenase (alpha GPDH). The optical density of individual tensor tympani and gastrocnemius muscle fibres after different incubation procedures was measured photometrically. The absorbance values of the tensor tympani fibres were related to the values of the type I, type IIA and type IIB fibres of the gastrocnemius muscle. Only two different types of fibre could be demonstrated in the tensor tympani, one type resembling the type I and another resembling the type IIA of the gastrocnemius muscle. The findings are discussed in relation to other, recent immunohistochemical studies on cat tensor tympani muscle fibres.

Animals↗
PubMed1983

The locations of stapedius and tensor tympani motoneurons in the cat.

The numbers and locations of motoneurons to the stapedius and tensor tympani muscles were determined by retrograde transport of horseradish peroxidase. Stapedius motoneurons lay outside the traditionally recognized facial nucleus, in several distinct locations: (1) in the interface between the facial nucleus and the superior olive; (2) in a thin, scattered lamina of somewhat smaller cells spread dorsal to the facial nucleus; and (3) in a cluster located ventromedial to the rostral third of the facial nucleus. Some cells also lay dorsal to the superior olive or scattered in the reticular formation, just medial to the descending loop of the facial nerve. Tensor tympani motoneurons also lay outside the traditionally recognized trigeminal motor nucleus, in an area just ventral to it. Both motoneuron pools were large, producing innervation ratios that establish stapedius and tensor tympani among the most finely innervated muscles yet studied. The degree of intermingling of large and small cells in these pools may explain, in part, why it has been easier to identify slow muscle fibers physiologically in tensor tympani than in stapedius.

Animals↗
PubMed1969

The occurrence, structure and innervation of slow and twitch muscle fibres in the tensor tympani and stapedius of the cat.

1. The muscle fibres of the tensor tympani and stapedius of the cat have been examined in the light microscope in teased preparations after cholinesterase staining and in the electron microscope.2. In both muscles, two kinds of fibre have been found: those with an individual end-plate and those with multiple nerve terminals.3. The stapedius fibres with an end-plate have fibrils regularly separated from each other by sarcoplasmic reticulum, a straight Z line, transverse tubular T system elements regularly occurring at the junction of A and I bands, an M line, an extensive sole plate area, and numerous post-junctional sarcolemmal infoldings under the nerve terminal. This type of muscle fibre in the tensor tympani has all of these features except that the fibrils are not well separated from each other, T system elements are absent in some sarcomeres, and a typical M line is absent.4. Compared to the individually innervated fibres, the fibres with multiple endings have fibrils poorly separated from each other by sarcoplasmic reticulum, a jagged Z line, very few T system elements, a less extensive sole plate area, and essentially no folds under the nerve terminal. These fibres in both muscles have M lines.5. Muscle fibres have thus been found in both the tensor tympani and stapedius of the cat which conform in their innervation, the structure of their motor nerve endings, and their internal structure to many of the morphological characteristics which are exhibited by slow muscle fibres elsewhere.

Animals↗
PubMed1982

Localization of motoneurons innervating the tensor tympani muscles: an horseradish peroxidase study in the guinea pig and cat.

Motoneurons innervating the tensor tympani muscle were identified in the adult guinea pig and cat by the horseradish peroxidase (HRP) method. After HRP injection into the tensor tympani muscle, HRP-labeled neurons were seen in the regions outside the cytoarchitectonically-defined confines of the trigeminal motor nucleus; in the regions rostral to the rostral pole of the nucleus, as well as in the regions ventral and ventrolateral to the nucleus at the levels of the rostral half (guinea pig) or the rostral two-thirds (cat) of the nucleus. The tensor tympani motoneurons were generally smaller than the masticatory motoneurons.

Animals↗
PubMed2003

Is there a double innervation of the tensor tympani muscle in humans?

The middle ear muscles and their function have not yet been fully explored. The statement of Lawrence, for example, that the tensor tympani muscle of humans might have a dual innervation has never been proven or disproven. The question is of great interest; in our opinion, it represents one of the key questions in the putative afferent feedback loop of the middle ear muscles in humans. A light microscopic study was performed on 16 tensor tympani muscles taken from 11 cadavers. Six muscles were taken out in toto and stained according to the modified method of Sihler. The remaining 10 muscles were dehydrated and embedded in paraffin. In 5 of these muscles, complete transverse serial sections were made on a microtome at 7 microm and alternately stained by silver impregnation, S-100 protein immunohistochemistry, and ferric oxide. In the remaining 5 muscles, complete longitudinal serial sections were made at 10 microm. These sections were alternately stained by the methods of Cason and Maskar. Neither the surgical microscopic investigation nor the light microscopic investigation revealed any innervation to the human tensor tympani muscle other than the one arising from the mandibular branch of the trigeminal nerve. Our findings, apart from the fact that they clearly refute an unproven hypothesis, might represent another small step toward understanding the innervation of the tensor tympani muscle.

Histocytological Preparation Techniques↗
PubMed1991

Neonatal myosin in bovine and pig tensor tympani muscle fibres.

In previous studies of middle ear muscles, the classification of fibre types by histochemical methods was particularly difficult in the bovine and porcine tensor tympani muscle, suggesting the presence of immature fibres. We therefore reexamined the tensor tympani from pigs and cattle of various ages immunohistochemically, using a panel of antimyosin antibodies, including one (anti-NE) specific for neonatal and embryonic myosins. Fibres positive to anti-NE were found in tensor tympani in both species in all ages examined; only a few of these fibres reacted exclusively with this antibody; some also contained slow myosin and the majority also contained adult fast (type IIA) myosin. Furthermore, although the remaining fibres included some of the classical types I and IIA, the majority of them showed a mismatch between their histochemical and immunohistochemical profiles. The morphological appearance of the muscle, the widespread presence of neonatal myosin (often together with another myosin in the same fibre) and the persistence of this composition from birth to adulthood, could be explained by an incomplete development of the muscle fibres, resulting in a 'muscle' much better suited to the role of a ligament.

Aging↗
PubMed1983

Further observations concerning the motor innervation of the tensor tympani muscle of the cat.

The cat tensor tympani muscle presented an uncommon ultrastructural organization of neuromuscular junctions compared with those in the other striated muscles. In cross sections, individual neuromuscular junctions had very extended contact area of the nerve terminal and muscle fiber, the terminal bouton was covering as a "calyx" the postjunctional muscle fiber. Long basal lamina was interposed between them. The sarcolemma at the level of the nerve terminal had multiple infoldings along its length, or smooth postjunctional muscle membrane was found beneath endings on both fiber types.

Animals↗
PubMed1984

Identification of motoneurons innervating the tensor tympani muscle in the rabbit: a retrograde horseradish peroxidase study.

After injecting horseradish peroxidase into the tensor tympani muscle in the rabbit, neuronal cell bodies labeled retrogradely with the enzyme were seen in the ventrolateral regions of the pontine tegmentum. These tensor tympani motoneurons were located in the 'nucleus n' as well as in the rostrodorsal part of the medial 'cell group k' of Meessen and Olszewski [4].

Animals↗
PubMed1998

Serotoninergic innervation of stapedial and tensor tympani motoneurons.

Retrograde tracing and neurotransmitter immunohistochemistry were combined to determine whether serotonin neurons innervated stapedial and tensor tympani motoneurons. With high-power light microscopy, putative axo-somatic and axo-dendritic contacts were observed between serotonin-positive endings and both stapedial and tensor tympani motoneurons, indicating that serotonin neurons terminate on brainstem motoneurons innervating the middle-ear muscles. With this connection, the serotonin system may directly modulate middle-ear muscle activity.

Immunohistochemistry↗