ULTRASTRUCTURE OF THE SUPPORTING CELLS IN THE PARATYMPANIC ORGAN OF CHICKEN, GALLUS-GALLUS-DOMESTICUS

The paratympanic organ is a specialized sensory organ of birds located in the medial wall of the tympanic cavity. It possesses a sensory epi thelium formed by type II hair cells and supporting cells. The support ing cells are tall, narrow units that extend from the basement membran e to the free epithelial surface. They show a fine structure character ized by numerous mitochondria, a conspicuous Golgi complex and a well- developed RER. Moreover, some uncommon structures, probably formed by heaped RER cisternae, are frequently present in the cytoplasm. Adjacen t supporting cells are connected by numerous and extensive gap junctio ns; moreover, small gap junctions between hair cell and supporting cel ls are to be found. The possible mechanical and metabolical functions of the paratympanic organ supporting cells are discussed. (C) 1998 Wil ey-Liss, Inc.