Experimental alteration of the rat skull base and its effect upon the position of the larynx and hyoid bone.
Item
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Title
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Experimental alteration of the rat skull base and its effect upon the position of the larynx and hyoid bone.
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Identifier
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AAI8914780
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identifier
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8914780
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Creator
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Reidenberg, Joy Spring.
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Contributor
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Adviser: Jeffrey T. Laitman
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Date
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1988
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Anatomy | Biology, General | Biology, Zoology
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Abstract
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Laryngeal position is important for regulating a mammal's breathing, swallowing, and vocalizing abilities. A larynx located high in the neck allows for simultaneous respiration and deglutition, while a larynx positioned low in the neck increases the area available as a resonating chamber for laryngeal sounds.;This study investigates the relationship between basicranial shape and the position of the larynx and hyoid bone. Comparative anatomical dissections reveal that a flat skull base and high larynx is the typical mammalian pattern, found in both terrestrial and aquatic species. The flexed skull base and low larynx is characteristic of adult humans. The relationship between the skull base and the upper respiratory tract is explored in an experimental study utilizing rats. Basicranial flexion was artificially induced and any resulting effects on laryngeal and hyoidal position recorded.;The spheno-occipital synchondrosis was surgically ablated with a dental drill in 129 infant rats at 13 days of age. Sham operations were performed on 15 rat pups at 13 days old. Eighteen normal control rats were used for comparison. Radiopaque dye was placed on the soft palate, epiglottis, and valleculae to visualize the larynx, and lateral radiographs were taken at 40, 60, 80, 100, and 120 days. Angular measurements of basicranial contour and the position of the larynx and the hyoid bone were recorded. Changes in overall skull shape were also monitored. Rats were sacrificed at 130 days and the skull base examined histologically.;Results indicate that removal of the spheno-occipital synchondrosis induces flexion (kyphosis) and shortening of the basicranium, arching of the cranial vault, and an endocranial elevation resembling the human dorsum sellae and clivus. The induced basicranial flexion caused the larynx and hyoid bone to be inferiorly displaced. Statistical analysis shows significant differences between experimental and control groups for basicranial, hyoidal, and laryngeal angles, and an inverse correlation for basicranial vs. hyoidal angles, and basicranial vs. laryngeal angles. Histological examination reveals a premature formation of a synostosis between the basisphenoid and basioccipital bones.;These results reveal that larynx and hyoid positions are affected by changes in the shape of the basicranium, thus indicating a mechanical relationship between the skull and upper respiratory tract structures.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
