ISSN:0006-8977    

DOI:10.1159/000124333

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000124334

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000124335

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Classical and modern studies of the labyrinth have established that the inner ear exhibits orderly sequences of changes that can be correlated with the phylogenesis of the taxa in which they occur; such sequences are evident at histological and cytological levels, as well as morphological ones. Conditions in living fishes and fishlike animals suggest that a primary evolutionary thrust, involving establishment of an effective equilibratory system, must have been essentially complete at the time of origin of the bony fishes. Concurrently with morphological changes in the labyrinth, the neuroepithelium of the vestibular receptors established patterns of polarization similar to those in higher vertebrates, but it apparently remained conservative in its architecture and patterns of innervation. Except for the ampullary crests, these receptors may have additionally been capable of responding to vibratory stimuli, but they are known to show auditory specializations only in cases where effective mechanisms for mechanical transmission have developed (e.g., clupeids, ostariophysians). It may reasonably follow that marked labyrinthine changes accompanied establishment of a columellar apparatus in early amphibians; these undoubtedly included differentiation of periotic channels and a primitive basilar papilla. Modern amphibians exhibit variations of a divergent set of labyrinthine specializations. The amphibian papilla, possibly partially homologous to the papilla neglecta, tends to be the more prominent of the two auditory receptors present; the basilar papilla, although represented in all orders, is significantly developed only in anurans. Rather elaborate morphological specializations are known to be associated with both receptors but, aside from absence of efferent innervation in the anuran basilar papilla, no major fine structural modifications have been reported to occur in the neuroepithelium of either.The combination of structures requisite to direct derivation of the avian and mammalian inner ear probably appeared quite early in reptilian stem stock. In living reptiles, the cochlear duct and its parts show several lines of modification; of particular interest are histological and cytological changes in the basilar papilla.Squamate forms (amphisbaenians, snakes, lizards) show varying stages of specilization in the supporting cells, in the morphology, polarization and innervation of hair cells, and in the tectorial membrane. Extreme changes are evident in most crocodilian sensory and supporting cells, but some neuroepithelial elements demonstrate transitional modifications. Cytological specializations closely related to those in crocodilians are evident in the avian basilar papilla. It is of interest that several of the types of change noted are similar to those which would be required to derive a mammalian organ of Corti from a primitive neuroepithelium.

ISSN:0006-8977    

DOI:10.1159/000124300

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The statoconia of goldfish, ray, frog and pigeon were investigated by the use of light and electron microscopes. Concentric lamellation of daily ''growth rings'' reported earlier was observed. This lamellation was formed by alternating slow-growth bands and fast-growth bands. The former contains more protein matrix than the latter. The ray statoconia are comprised of grains of sand (exogenous) and round crystals with internal lamellation (endogenous?). The frog statoconia are made of numerous crystals which contain a large amount of protein matrix as in the mammalian statoconia.

ISSN:0006-8977    

DOI:10.1159/000124301

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The general shape of the cupula conformsto the receptor area from which it arises. In the vertical canals of the frog, the cristae have an overall dumbbell shape; the cupula has corresponding enlarged masses which project from the expanded receptor ends while the central portion, which is about one third as thick, completes the diaphragm. The horizontal canal crista has a single enlarged end (club shaped) and consequently has a single cupular mass extending along one side of the ampulla up to the apex. A thinner portion extends to the opposite ampullar wall. In the vertical canals the enlarged masses end before the summit such that the thinner center reaches the apex.The cupula forms a tight diaphragm across the ampulla which is most easily displaced at the center. The central zone of the crista serves to position hair cells about one third the distance to the center of the ampulla while the ends of the crista are more peripherally located in relation to the diaphragm. A graded response to diaphragmatic displacement results. The apex of the cupula is most labile to detachment but not initial displacement. This region can act as a relief valve such that once displacement of the diaphragm has reached its maximum for the base of the cupula, the apical end is displaced and ultimately detached. This mechanism serves to prevent damage to the receptor structure and its cupular relationship.The cupula is composed of two components: filamentous material (protein) and an amorphous substance (mucopolysaccharide). The protein is related to supporting cells and the distal end of the kinocilium. The mucopolysaccharide is secreted from cuboidal cells which surround the receptor area and may serve as a binding substance.From the saddle-shaped receptor surface ciliary tufts consisting of 3 or 4 rows of short stereocilia project into the lumen and a single row of 5 or 6 of these processes continues across the subcupular space (60–70 µm) accompanied by a single kinocilium. The kinocilium continues into the filamentous and mucopolysaccharide matrix of the cupula to form a linkage between the receptor cells and the cupula. Scattered binding filaments are found between the kinocilium and adjacent stereocilia which are similar to those described in the saccule and utric

ISSN:0006-8977    

DOI:10.1159/000124302

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The anatomy of the peripheral auditory system of the alligator lizard, Gerrhonotus multicarinatus, is described. The histology of the auditory receptor (basilar papilla) is described in detail and compared with the mammalian organ of Corti. Special features of the cochlear anatomy are correlated with intracellular responses recorded within the basilar papilla. The cochlea of the alligator lizard is a suitable preparation for combined morphological and electrophysiological investigations of sensory transduction at the cellular level in a vertebrate inner ear.

ISSN:0006-8977    

DOI:10.1159/000124303

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The basilar papilla of the lizard Calotes versicolor contains two different types of sensory cells. The ventral part of the organ is populated by the short-haired type A sensory cells whereas the dorsal part is populated by the long-haired type B sensory cells. The type A sensory cells are all unidirectionally oriented away from the cochlear nerve while the type B cells are bidirectionally oriented towards the midline of the organ. The ventral part of the basilar papilla, that is the type A sensory cell population, is covered by a tectorial membrane. Close to the base of the stereocilia in the sensory hair bundle a connective zone is seen linking them together. At the top of the kinocilium thin filaments are seen bridging the gap to the closest stereocilia, thus linking the kinocilium to the rest of the sensory hair bundle. Fine filaments are also seen linking the bulbous tip of the type A sensory cell kinocilium with the tectorial membrane.

ISSN:0006-8977    

DOI:10.1159/000124304

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The papillae basilares of species ofeight families of lizards have been studied by scanning electron microscopy. Two basic types of simpler papillae basilares are found in species of three families, namely the Iguanidae, Agamidae and Anguidae. The papillae in all these families contain both short and long-ciliated hair cells; the region of short-ciliated hair cells may be either central or apical in location. Species of lacertid, teiid and varanid lizards show possibly more advanced papillae made up only of short-ciliated hair cells. Species of gekkonid and scincid lizards have what are probably more advanced types of papillae, each with peculiar modifications. All lizard papillae basilares exhibit simple or complex kinocilial bidirectionality as well as a limited region of kinocilial unidirectionality.

ISSN:0006-8977    

DOI:10.1159/000124305

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000124338

出版商:S. Karger AG    

年代:1974

数据来源: Karger