Myoepithelial cells are observed in several exocrine glands. They are star-shaped cells that lie in between the basal lamina and the acinar and ductal cells (Ogawa et al., 1999)³⁰. These cells have the structural fea­tures and function of both smooth muscle cells and epithelium (Franke et al., 1980)³¹. They contract when the gland is stimulated to secrete. They aid expulsion of glandular se­cretion through compressing or rein­forcing the underlying parenchyma! cells, it was suggested that the major function of myoepithelial cells in sali­vary glands is to support the glandu­lar structure through isometric con­traction (Segawa et a!., 1995)³⁶. They also display the characteristics of epithelium in that they are situated
within the glandular epithelium be­tween secretory cells and the base­ment membrane (Tandler, 1965; Harrop, 1968; Leeson and Leeson, ₁₉₇₁)45,19,26
Myoepithelial cells have speculat­ed to play an important role in histo-genesis of some salivary gland tu­mors, such as pleomorphic adenoma, myoepithelioma, adenoid cystic carci­noma and certain other tumors (Bat-sakis et al., 1983; Dardick and Bu-
ford-Mason, 1993; Redman, 1994) 2,9,33.
Studies of the responses of SMG to ligation of the main excretory duct have established that both acinar cells and cells of the granular ducts are markedly altered morphologically