Functional morphology of myoepithelial cells in the rat salivary glands: A review

Abstract

Background: The acini, the secretory endpieces of the salivary glands, are composed of serous and/or mucous acinar cells and surrounded by myoepithelial cells. Myoepithelial cells are multipolar, stellate cells with long processes encircling the acini and intercalated ducts. These cells contract to facilitate salivary secretion and transport.

Highlight: In rat major salivary gland acini, the morphology of myoepithelial cells varies across glands: parotid glands lack myoepithelial cells, submandibular glands contain "slender"-shaped cells, and sublingual glands contain "macho"-shaped cells. These morphological variations are thought to depend on the salivary viscosity. Myoepithelial cells in the intercalated ducts exhibit minimal variation across the major salivary glands, with processes oriented parallel to the duct axis. These cells are covered by a thin collagen layer and small fibroblasts, collectively termed "the peri-intercalated duct sheath." Ebner's glands, located beneath the circumvallate and foliate papillae and containing numerous taste buds, develop myoepithelial cells in both the acini and intercalated ducts to facilitate vigorous saliva secretion, enhancing gustatory sensitivity.

Conclusions: The morphology of myoepithelial cells is influenced by their functional roles under different anatomical, physiological, and pathological conditions. Increased thickness and branching occur to adapt to salivary viscosity and/or enhance secretion. In the intercalated ducts, myoepithelial cells support salivary transport with the aid of the surrounding collagen layer and fibroblasts in "the peri-intercalated duct sheath".

Keywords: Acinar type; Duct type; Myoepithelial cells; Rat; Salivary glands.