 | Skull, Bone & CartilageIn E14 chick embryos (second trimester) the temporal bones are partially calcified (red), but the majority of the skull bones are cartilagenous (blue). The incubation period of chicks is 21 to 29 days in most species. Chicks are like human precocious at birth because they hear and see immediately after hatching. We favor birds to inner ear studies for these reason. Rodents (also short gestational periods) are born blind and deaf. |
 | Avian LabyrinthLike its human counterpart, the membranous portion of the inner ear forms twisted passages referred to as a labyrinth. Each conduit is designed in such a manner that movement of the head in any direction stimulates hair cells to interprete motion sending the sensetions to the brain. |
 | From the inner ear to the brainWe sense motion and sound waves because the inner ear is capable of efficiently translating mechanical changes into neural stimuli. The process is complex and its understanding requires years of training. |
 | The cable that connectSpecialized cells called bipolar neurons because of their two branches connect the hair cells to the brain centers. Proper functioning of the neurons and of the hair cells is interconnected. Neurons from one portion of the nerve are more plastic than from the other. |
 | Bipolar NeuronsThe specialized bipolar neurons were studied in detail back in the 80's (see Fermin and Igarashi Publications). Bipolar neurons form the auditory and vestibular ganglia, but only the bipolar vestibular neurons survive deafferentation longer than 3 years in large enough numbers to suggest possible functional attributes after repair. |
 | Hair cells (microphones) for equilibriumSimilar to two different groups of neurons in the nerve (cables), there are two types of microphones attached to the cables. The hair cells (microphones) are specialized neurons (paraneurons) with extremally sophisticated functions. |
 | Hair cells (microphones) for HearingThe function of each cell group is different, and so is the manner in which the neurons (cables) contact the hair cells (microphones). |
 | Complex control-nicheThe inner ear in a the space of a pea has more functions than bigger organs. Most epithelial type of the body are found in the inner ear making analysis of seggregated components very difficult. To make matters worse, the temporal bone that houses the inner ear is the hardest of the body. Despite these shortcomings otolaryngolists (clinician and basic scientists) have made great progress toward the understanding of inner ear properties. |
 | Complex control-nicheEach color of this image corresponds to different cell types (sensory and non-sensory) and spaces between them must kept separated and ionically balanced or hearing and equilibrium become pathologic. The twisted duct that house the inner ear maintains the seggreation despicted here. Ataxia, disorientation, dizziness occur when the fluids of the perilymph and endolymph mix, and such is the case in Meniere's disease. |
 | Sodium & PotassiumThese cations are essential for the functioning of the hair cell. Their osmolality is controlled by specialized cells of the inner ear able to move these cations and calcium across barriers of the cell membranes. Of interest in this regard is that aminoglycosides antibiotics (e.g., streptomycin) and diuretics disrupt the electrolytic balance of these cations and can produce serious inner ear disturbances (dizzness, disorientation, etc). |
 | Dark & Light cellsIn birds, the function of dark and light cells in the tegmentum vasculosum was demonstrated by Dohlman decades ago (see Fermin et al, 1995 for details and appropriate credit to him). Recent work with modern techniques and equipment contributed further to our understanding of these cells functioning. We concentrate on the in vivo system and to that end, try to analyze tissues and cell rather than molecules in cells. We favor this "black box" approach because in the end, if findings are not reproduceable in intact organs, the contribution of isolated findings is not meaningfull |
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