Morphological and morphometrical study of the auditory ossicles in chinchilla (original) (raw)
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Morphological and morphometrical aspects of the auditory ossicles in goat (Capra hircus)
2020
The present paper deals with a detailed description of the auditory ossicles in Capra hircus. The paper focuses on the morphological and morphometrical description of the ossicular assembly, formed by malleus, incus and stapes. The malleus (overall length, as average‐ 8.16 mm) comprises the head of malleus (Caput mallei), a slightly strictured part—neck (Collum mallei) with 3 distinctive processes (lateral, rostral and muscular) (Processus lateralis, Processus rostralis and Processus muscularis) and a handle (Manubrium mallei). The head of malleus has an oval aspect with an obtuse articular surface on its medial surface (Facies articularis). The neck is evident with three bony processes described—the anterior, almost triangular, the muscular one quite reduced and the lateral one which is the most developed one. The manubrium is the longest sector—4.4 mm and appears as a slightly curved piece. The incus presents a body of 1.3 mm and two processes—the short and long crus (Crus breve a...
The Journal of the Acoustical Society of America
The responses of the malleus and the stapes to sinusoidal acoustic stimulation have been measured in the middle ears of anesthetized chinchillas using the M6ssbauer technique. With "intact" bullas (i.e., dosed except for venting via capillary tubing), the vibrations of the tip of the malleus reach a maximal peak velocity of about 2 mm/s in responses to 100-dB SPL tones in the frequency range 500-6000 Hz; vibration velocity diminishes toward lower frequencies with a slope of about 6 dB/oct. Opening the bulla widely increases the responses to lowfrequency stimuli by as much as 16 dB. At low frequencies, malleus response sensitivity with either open or intact bullas far exceeds all previous measurements in cats and matches or exceeds such measurements in guinea pigs. Whether measured in open or intact bullas, phaseversus-frequency curves closely approximate those predicted from the magnitude-versusfrequency curves by minimum phase theory. The stapes responses are similar to those of the malleus, except that stapes response magnitude is lower, on the average, by 7.5 dB at frequencies below 2 kHz and 10.7 dB at 2 kHz and above. Comparison of the responses of the middle ear with those of the basilar membrane at a site 3.5 mm from the stapes indicates that, at frequencies below 150 Hz, the basilar membrane displacement is proportional to stapes acceleration. At frequencies between 150 and 2000 Hz, basilar membrane displacement is proportional to stapes velocity. PACS numbers: 43.64.Ha, 43.64.Kc basilar membrane, hair cells, cochlear afferents) in situ, in the same species and, preferably, in the same laboratory, utilizing standardized techniques. We have focused on the responses of the chinchilla auditory periphery to low-frequency tones, describing these responses at the levels of the auditory nerve, cochlear microphonics and the basilar membrane (Ruggero and Rich, 1983, 1987, and 1989; Ruggero et al., 1986b-d). The latter measurements are, of necessity, performed with widely opened bullas, while the auditorynerve measurements have been often obtained with the bulla vented via a single small hole. Therefore, a principal motivation of the present study is to ascertain the extent to which •Portions of this paper were presented previously [Ruggero et al., Sac. Neurosei. Abstr. 12, 7.78 (1986) ]. MI 48202. the input to the cochlea (middle-ear ossicular motion) is affected by opening the bulla cavity. A second motivation for this investigation is to specify stapes motion as a function of pressure at the tympanic membrane, so as to permit computation of the cochlea-specific contributions to the response of the chinchilla basilar membrane. This question is of interest because there is evidence that low-frequency cooblear responses can be quite different in different species and, in particular, that the chinchilla basilar membrane displacement at very low frequencies is proportional to stapes acceleration (Dallos, 1970; Ruggero et al., 1986a,b), rather than stapes velocity, as is the case for the guinea pig and squirrel monkey (e.g., Johnstone and Taylor, 1970; Rhode, 1971). Finally, the study of the middle ear of the chinchilla is interesting in itself, given the widespread use of this species in auditory research. While many studies have measured middie-ear vibration in the cat and guinea pig (see TaMe IIl) and in other mammalian species (Rhode, 1971 and 1978; Wilson and Bruns, 1983; Relkin and Saunders, 1980; Aitkin and Johnstone, 1972), no such measurements have yet been published for the chinchilla. ß METHODS A. Animal preparation All experimental procedures, including surgery and all measurements of middle ear vibration, were carried out in live chinchillas anesthetized with sodium pentobarbital (initial dose: 65 mg/kg intraperitoneally, with additional doses as required to maintain deep anesthesia}. The animals were 1612
Biology
Otological studies rely on a lot of data drawn from animal studies. A lot of pathological or evolutionary questions may find answers in studies on primates, providing insights into the morphological, pathological, and physiological aspects of systematic biological studies. Our study on auditory ossicles moves from a pure morphological (macroscopic and microscopic) investigation of auditory ossicles to the morphometrical evaluation of several individuals as well as to some interpretative data regarding some functional aspects drawn from these investigations. Particularities from this perspective blend with metric data and point toward comparative elements that might also serve as an important reference in further morphologic and comparative studies.
Structures that contribute to middle-ear admittance in chinchilla
Journal of Comparative Physiology A, 2006
We describe measurements of middle-ear input admittance in chinchillas (Chinchilla lanigera) before and after various manipulations that define the contributions of different middle-ear components to function. The chinchilla's middle-ear air spaces have a large effect on the lowfrequency compliance of the middle ear, and removing the influences of these spaces reveals a highly admittant tympanic membrane and ossicular chain. Measurements of the admittance of the air spaces reveal that the high-degree of segmentation of these spaces has only a small effect on the admittance. Draining the cochlea further increases the middle-ear admittance at low frequencies and removes a low-frequency (less than 300 Hz) level dependence in the admittance. Spontaneous or sound-driven contractions of the middle-ear muscles in deeply anesthetized animals were associated with significant changes in middle-ear admittance.
Macroanatomic structure and morphometric analysis of middle ear in ostrich (Struthio camelus)
Ostrich (Struthio camelus) is a species belonging to the Struthionidae family of Struthioniformes order that does not have the flying ability among birds. The aim of this study was to make a subgross investigation on anatomical structures of middle ear in ostrich and to determine the morphometry of the columella. In the present study, 4 adult ostrich heads were used in the study. Tympanic cavity and the formations inside are removed from the skull by protecting the cranial roof. Subgross examinations of tympanic cavity, columella and other anatomic structures were then performed, and morphometric measurements of columella and some anatomical structures were performed using a digital calliper. It was determined that tympanic cavity, surrounded by ear capsule (os oticum), had a conical shape and was covered with mucosa that was tightly adjacent to the periosteum. Tympanic membrane, columella and osteochondral structures, ligaments, a branch of external ophthalmic artery and the presence of chorda tympani were detected in tympanic cavity. It was observed that columella was placed diagonally in tympanic cavity. The vestibular (proximal) end having a circular shape was found to have a large basis and annular ligament which ended up with thickened, small columns. Finally we demonstrated anatomy and morphometric values of middle ear in ostrich. The anatomy and formations of the middle ear are clearly shown. It can be asserted that anatomical formations in the middle ear of an ostrich are similar to other birds.
Middle-ear response in the chinchilla and its relationship to mechanics at the base of the cochlea
The Journal of the Acoustical Society of America, 1990
The responses of the malleus and the stapes to sinusoidal acoustic stimulation have been measured in the middle ears of anesthetized chinchillas using the M6ssbauer technique. With "intact" bullas (i.e., dosed except for venting via capillary tubing), the vibrations of the tip of the malleus reach a maximal peak velocity of about 2 mm/s in responses to 100-dB SPL tones in the frequency range 500-6000 Hz; vibration velocity diminishes toward lower frequencies with a slope of about 6 dB/oct. Opening the bulla widely increases the responses to lowfrequency stimuli by as much as 16 dB. At low frequencies, malleus response sensitivity with either open or intact bullas far exceeds all previous measurements in cats and matches or exceeds such measurements in guinea pigs. Whether measured in open or intact bullas, phaseversus-frequency curves closely approximate those predicted from the magnitude-versusfrequency curves by minimum phase theory. The stapes responses are similar to those of the malleus, except that stapes response magnitude is lower, on the average, by 7.5 dB at frequencies below 2 kHz and 10.7 dB at 2 kHz and above. Comparison of the responses of the middle ear with those of the basilar membrane at a site 3.5 mm from the stapes indicates that, at frequencies below 150 Hz, the basilar membrane displacement is proportional to stapes acceleration. At frequencies between 150 and 2000 Hz, basilar membrane displacement is proportional to stapes velocity. PACS numbers: 43.64.Ha, 43.64.Kc basilar membrane, hair cells, cochlear afferents) in situ, in the same species and, preferably, in the same laboratory, utilizing standardized techniques. We have focused on the responses of the chinchilla auditory periphery to low-frequency tones, describing these responses at the levels of the auditory nerve, cochlear microphonics and the basilar membrane (Ruggero and Rich, 1983, 1987, and 1989; Ruggero et al., 1986b-d). The latter measurements are, of necessity, performed with widely opened bullas, while the auditorynerve measurements have been often obtained with the bulla vented via a single small hole. Therefore, a principal motivation of the present study is to ascertain the extent to which •Portions of this paper were presented previously [Ruggero et al., Sac. Neurosei. Abstr. 12, 7.78 (1986) ]. MI 48202. the input to the cochlea (middle-ear ossicular motion) is affected by opening the bulla cavity. A second motivation for this investigation is to specify stapes motion as a function of pressure at the tympanic membrane, so as to permit computation of the cochlea-specific contributions to the response of the chinchilla basilar membrane. This question is of interest because there is evidence that low-frequency cooblear responses can be quite different in different species and, in particular, that the chinchilla basilar membrane displacement at very low frequencies is proportional to stapes acceleration (Dallos, 1970; Ruggero et al., 1986a,b), rather than stapes velocity, as is the case for the guinea pig and squirrel monkey (e.g., Johnstone and Taylor, 1970; Rhode, 1971). Finally, the study of the middle ear of the chinchilla is interesting in itself, given the widespread use of this species in auditory research. While many studies have measured middie-ear vibration in the cat and guinea pig (see TaMe IIl) and in other mammalian species (Rhode, 1971 and 1978; Wilson and Bruns, 1983; Relkin and Saunders, 1980; Aitkin and Johnstone, 1972), no such measurements have yet been published for the chinchilla. ß METHODS A. Animal preparation All experimental procedures, including surgery and all measurements of middle ear vibration, were carried out in live chinchillas anesthetized with sodium pentobarbital (initial dose: 65 mg/kg intraperitoneally, with additional doses as required to maintain deep anesthesia}. The animals were 1612
Hearing Research, 2016
While the cochlea is considered the primary site of the auditory response to bone conduction (BC) stimulation, the paths by which vibratory energy applied to the skull (or other structures) reaches the inner ear are a matter of continued investigation. We present acoustical measurements of sound in the inner ear that separate out the components of BC stimulation that stimulate the inner ear via ossicular motion (compression of the walls of the ear canal or ossicular inertia) from the components that act directly on the cochlea (cochlear compression or inertia, and extra-cochlear 'third-window' pathways). The results are consistent with our earlier suggestion that the inner-ear mechanisms play a large role in bone-conduction stimulation in the chinchilla at all frequencies. However, the data also suggest the pathways that conduct vibration to the inner ear via ossicularmotion make a significant contribution to the response to BC stimulation in the 1 to 3 kHz range, such that interruption of these path leads to a 5 dB reduction in total stimulation in that frequency range. The mid-frequency reduction produced by ossicular manipulations is similar to the 'Carhart's notch' phenomenon observed in otology and audiology clinics in cases of human ossicular disorders. We also present data consistent with much of the ossicular-conducted sound in chinchilla depending on occlusion of the ear canal.
Ontogenetic and phylogenetic transformations of the ear ossicles in marsupial mammals
Journal of Morphology, 2001
This study is based on the examination of histological sections of specimens of different ages and of adult ossicles from macerated skulls representing a wide range of taxa and aims at addressing several issues concerning the evolution of the ear ossicles in marsupials. Three-dimensional reconstructions of the ear ossicles based on histological series were done for one or more stages of Monodelphis domestica, Caluromys philander, Sminthopsis virginiae, Trichosurus vulpecula, and Macropus rufogriseus. Several common trends were found. Portions of the ossicles that are phylogenetically older develop earlier than portions representing more recent evolutionary inventions (manubrium of the malleus, crus longum of the incus). The onset of endochondral ossification in the taxa in which this was examined followed the sequence; first malleus, then incus, and finally stapes. In M. domestica and C. philander at birth the yet precartilaginous ossicles form a supportive strut between the lower jaw and the braincase. The cartilage of Paauw develops relatively late in comparison with the ear ossicles and in close association to the tendon of the stapedial muscle. A feeble artery traverses the stapedial foramen of the stapes in the youngest stages of M. domestica, C. philander, and Sminthopsis virginiae examined. Presence of a large stapedial foramen is reconstructed in the groundplan of the Didelphidae and of Marsupialia. The stapedial foramen is absent in all adult caenolestids, dasyurids, Myrmecobius, Notoryctes, peramelids, vombatids, and phascolarctids. Pouch young of Perameles sp. and Dasyurus viverrinus show a bicrurate stapes with a sizeable stapedial foramen. Some didelphids examined to date show a double insertion of the Tensor tympani muscle. Some differences exist between M. domestica and C. philander in adult ossicle form, including the relative length of the incudal crus breve and of the stapes. Several differences exist between the malleus of didelphids and that of some phalangeriforms, the latter showing a short neck, absence of the lamina, and a ventrally directed manubrium. Hearing starts in M. domestica at an age in which the external auditory meatus has not yet fully developed, the ossicles are not fully ossified, and the middle ear space is partially filled with loose mesenchyme. The ontogenetic changes in hearing abilities in M. domestica between postnatal days 30 and 40 may be at least partially related to changes in middle ear structures.
Morphological and morphometrical anatomy of the auditory ossicles in roe deer (Capreolus capreolus)
The European Zoological Journal
The study provides a series of distinctive morphological features of the auditory ossicles alongside comparative morphometric data, bringing facts in respect to morphology and some morpho-functional elements of the auditory ossicles in this little-studied species. The most relevant features noted are evident conical shape of muscular process of malleus and triangular aspect of the handle of malleus. For the incus, a short body of the bone and the direct continuation is mentioned, with no clear distinction as an individualized piece for the lenticular process. As for the stapes, the clear profiling of the muscular tubercle for the stapedial muscle and elliptic shape of the foot of the stapes is noted. A series of comparative measurements and indices are also calculated in the attempt of profiling differences from the domestic couterspecies-sheep and goat.