Fine structure of the taste bud1,2

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An electron microscope study on the taste bud in the fungiform papilla of the adult rat tongue was performed. Four cell types, classified according to their location, morphology, and relation to intraepithelial nerve processes, are described. These are the peripheral, basal, type I (dark), and type II (light) cells.

The peripheral cells are located on the outer circumference of the lower half of the taste bud. They are characterized primarily by their high content of diffusely scattered RNP particles, their characteristic tubular filaments, and their lack of association with intraepithelial nerve processes. Peripheral cells are considered to be the precursors of all the other cell types in the taste bud.

Basal cells are located near the inferior pole of the central area of the taste bud. They are in proximity to one or more nerve processes. The basal cells are similar morphologically to peripheral cells except that they have a more extensive Golgi apparatus and, in that area of their cytoplasm adjacent to a nerve process, a cluster of small vesicles. This cell type is considered to be an intermediate form between peripheral cells and the type I and type II cells. The cluster of vesicles is thought to represent evidence for early differentiative changes in this intermediate cell type.

Type I cells are spindle-shaped and extend from the basement membrane to the taste pore. Microvilli project from the apical part of this cell type into the pore. The cytoplasm is characterized by the following: an abundance of delicate, filamentous material; lamellated, dense bodies; a prominent Golgi apparatus, but few other organelles. Tight junctions are formed between adjacent type I cells near their distal ends. This cell type usually envelops several intraepithelial nerve processes in a manner similar to that of Schwann cells. The type I cell is considered to be a taste receptor cell.

The type II cell cytoplasm is characterized by an abundance of mitochondria and variously sized vesicles and vacuoles. It is proposed that this cell plays a role in formation and maintenance of the taste pore.

The taste pore is usually plugged with amorphous dense material containing several, small, membrane-bounded vesicles, presumably of cellular origin.

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    1

    This investigation was supported by an Anatomy Training Grant (2G-297) from the National Institutes of Health, United States Public Health Service.

    2

    This study represents part of the work contained in a thesis submitted by the author to New York University as partial fulfillment of the requirements for the degree of Doctor of Philosophy.

    3

    Present address: Department of Anatomy, Northwestern University Dental School, 303 East Chicago Avenue, Chicago, Illinois.

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