Activities of salivary myoepithelial cells: a review.

Historical developments concerning salivary myoepithelial cells have been outlined and structural features of the cells have been described. Evidence from structural and functional studies supports the belief that myoepithelial cells usually have a dual innervation by parasympathetic as well as sympathetic nerves, and impulses from both types of nerve cause the cells to contract. Functional assessment using salivary flow phenomena and intraluminal pressure changes have been used to determine, so far as is possible, the effects of myoepithelial contractions. In some instances tissues have been examined structurally after such experimental procedures. These investigations indicate that salivary myoepithelial activity 1. Speeds up the outflow of saliva 2. Reduces luminal volume 3. Contributes to the secretory pressure 4. Supports the underlying parenchyma 5. Helps salivary flow to overcome increases in peripheral resistance. However, beyond a certain point, this may lead to sialectatic damage of striated ducts with increase in glandular permeability. Myoepithelial activity may also help to expel parenchymal cell contents in certain instances.