Digestive System Salivary Glands

Salivary Glands: Consist of two classes : The major salivary glands & the minor salivary glands.
• The major salivary glands are paired glands with long ducts that empty into the oral cavity.
• The major salivary glands, as noted above, consist of the paired parotid, submandibular, and sublingual glands.
• The parotid and the submandibular glands are actually located outside the oral cavity; their secretions reach the cavity by ducts.
• The sublingual gland is located in the floor of the mouth anterior to
• the submandibular gland.
• The minor salivary glands are located in the submucosa of different parts of the oral cavity. They include the lingual, labial, buccal, molar, and palatine glands.
• The major salivary glands are surrounded by a capsule of moderately dense connective tissue from which septa divide the secretory portions of the gland into lobes and lobules.
• The minor salivary glands do not have a capsule.
• Secretory acini are organized into lobules.
• Acini are of three types: serous, mucous, or mixed.
? Serous acini, which contain only serous cells and are generally spherical
? Mucous acini, which contain only mucous cells and are usually more tubular
? Mixed acini, which contain both serous and mucous cells. In routine H&E preparations, mucous acini have a cap of serous cells that are thought to secrete into the highly convoluted intercellular space between the mucous cells. Because of their appearance in histologic sections, such caps are called serous demilunes [Fr., half-moon].
• The basic secretory unit of salivary glands, the salivon, consists of the acinus, intercalated duct, and excretory duct (Fig.1). The acinus is a blind sac composed of secretory cells.
• Serous cells are protein-secreting cells.
• Serous cells have a pyramidal shape, with a relatively wide basal surface facing the basal lamina and a small apical surface facing the lumen of the acinus.
• Mucous cells are mucin-secreting cells.
• Mucus is synthesized and stored within the cell as mucinogen granules. When the product is discharged after hormonal or neural stimulation, the cell begins to resynthesize mucus.
• Myoepithelial cells are contractile cells that embrace the basal aspect of the acinar secretory cells.They lie between the basal plasma membrane of the epithelial cells and the basal lamina of the epithelium .
• Myoepithelial cells also underlie the cells of the proximal portion of the duct system. In both locations, the myoepithelial cells are instrumental in moving secretory products toward the excretory duct