Publisher Summary This chapter describes the cytology of salivary glands. The salivary glands are divided into two groups—major and minor. The parotid, submandibular (submaxillary), and sublingual glands are major salivary glands. The gross anatomical relationships of the salivary glands of mammals vary greatly between species. The nature of the secretory products of various salivary glands is widely investigated by histochemical staining methods. Staining methods for mucosubstances demonstrate that gross anatomically comparable glands from different species may secrete entirely different mucosubstances. The chapter discusses the secretory functions of the salivary glands. Salivary glands possess systems that allow these organs to secrete remarkable amounts of proteins, glycoproteins, and water. The secretory capacity of the salivary gland acinar cells has been well investigated, particularly the acinar cells of parotid glands. The synthesis, intracellular transport, storage, and discharge of exportable protein by exocrine-secreting cells are also discussed.

The cytology of salivary glands.

Properly speaking, the term, salivary gland should be taken as including any tissue that normally discharges a secretory product into the oral cavity. The functions of such secretions will include: 1. moistening of the buccal mucosa with the implied role of supporting oral hygiene and appetite; 2. providing lubrication to aid in the swallowing of solid and semisolid foodstuff; 3. providing enzymes destined to play a role in digestion; 4. providing an electrolyte-containing medium suitable for the solution and activation of salivary enzymes. Of course salivary glands may have other functions, such as the synthesis and secretion of hormones (Ellison, 1967; Ito, 1960; Levi-Montalcini and Angeletti, 1961, 1964; Levi-Montalcini and Cohen, 1960; Cohen, 1962; Cohen and Elliott, 1963; Cohen et al., 1972; Naughton et al., 1969; Weimar and Haraguchi, 1975), and the glands may be specialized to secrete venom (Pearson, 1942, 1950), but such functions will not be considered within the scope of the present article, which will be restricted to a consideration of trans-epithelial transport leading to the production of saliva subserving the normal functions as outlined above.

Transport in Salivary and Salt Glands

Ultrastructural localization of VIP-like immunoreactivity in large dense-core vesicles of 'cholinergic-type' nerve terminals in cat exocrine glands.

Subcellular fractionation of cat submandibular gland: Comparative studies on the distribution of acetylcholine and vasoactive intestinal polypeptide (VIP)

Salivary secretion is nerve mediated. The salivary glands are supplied by parasympathetic and sympathetic efferent nerves which travel to the glands by separate routes. Once in the glands the axons from each type of nerve intermingle and travel together in association with Schwann cells, forming Schwann-axon bundles. Two types of neuro-effector relationships exist with salivary parenchymal and myoepithelial cells: epilemmal (outside the parenchymal basement membrane) and hypolemmal (within the parenchymal basement membrane). Their relative frequencies with either type of nerve differ greatly between glands and species. Salivary blood vessels receive epilemmal innervations by both sympathetic and parasympathetic axons. The classical transmitters--acetylcholine in parasympathetic and noradrenaline in sympathetic axons--are stored in small vesicles. A variety of non-conventional neuropeptide transmitters have also been found in salivary nerves by immunohistochemistry, and they occur in large dense-cored vesicles. Prolonged high frequency stimulation has been found to cause depletion of large dense-cored vesicles from glandular nerves. In recent years afferent nerves have started to be identified and are found in greatest numbers around the main salivary ducts, where they may form a hypolemmal association with the epithelial cells. Functional studies demonstrate complex interactions between parasympathetic and sympathetic nerves. Morphological assessments of changes in the parenchymal cells after nerve stimulations or denervations add greatly to our understanding of the nerve functions. At least four types of influence can be exerted on salivary parenchymal cells by the nerves: hydrokinetic (water mobilizing), proteokinetic (protein secreting), synthetic (inducing synthesis), and trophic (maintaining normal functional size and state). In respect to each role, wide glandular and species differences exist between the relative contributions made by each type of nerve.

The innervation of salivary glands as revealed by morphological methods

THE LATENCY OF RESPONSE OE SECRETORY ACINAR CELLS TO NERVE STIMULATION IN THE SUBMANDIBULAR GLAND OF THE CAT

Jane Af Wilson

Papers

The latency of response oe secretory acinar cells to nerve stimulation in the submandibular gland of the cat

The Fine Structure of the Olfactory Tract of Carp.