Glandulas Salivales

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Note: Large images and tables on this page may necessitate printing in landscape mode. Copyright © The McGraw-Hill Companies. All rights reserved. Junqueira's Basic Histology: Text & Atlas, 12e > Chapter 16. Organs Associated with the Digestive Tract >

SALIVARY GLANDS
Exocrine glands in the mouth producesaliva, which has digestive, lubricating, and protective functions. With a usual pH of 6.5–6.9, saliva also has an important buffering function and in many nonhuman species is also very important for evaporative cooling. There are three pairs of large salivary glands: the parotid, submandibular, and sublingual glands (Figure 16–1), in addition to minor glands in mucosa and submucosa throughout theoral cavity which secrete 10% of the total volume of saliva.

Figure 16–1.

Major salivary glands. About 90% of saliva is produced by three bilateral pairs of salivary glands: the parotid, submandibular, and sublingual glands. Locations and relative sizes of these glands are shown here diagrammatically. These glands plus microscopic salivary glands throughout the oral mucosa produce 0.75 to1.50 L of saliva daily.

MEDICAL APPLICATION Reduced function of the major salivary glands due to diseases or radiotherapy is associated with caries, atrophy of the oral mucosa and speech difficulties. A capsule of connective tissue surrounds each major salivary gland. The parenchyma of each consists of secretory endpieces and a
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A capsule of connective tissue surrounds each major salivary gland. The parenchyma of each consists of secretory endpieces and a branching duct system arranged in lobules, separated by connective tissue septa originating from the capsule. The secretion of each gland is either serous, seromucous, or mucous, depending on itsglycoprotein mucin content. Saliva from the parotids is serous and watery. The submandibular and sublingual glands produce a seromucous secretion, with mostly mucus from the minor glands. Saliva is modified by the cells of the duct system draining the secretory units, with much Na+ and Cl– reabsorbed while certain growth factors and digestive enzymes are added. Two major kinds of secretory cellsoccur, arranged in separate units. Serous cells are polarized protein-secreting cells, usually pyramidal in shape, with a broad base resting on the basal lamina and a narrow apical surface facing the lumen (Figures 16–2 and 16-3). Adjacent cells are joined together by junctional complexes and usually form a spherical mass of cells called an acinus, with a very small lumen in the center (Figure 16–2).Acini and their duct system resemble grapes attached to a stem. Serous acinar cells largely produce digestive enzymes and other proteins.

Figure 16–2.

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Epithelial components of a submandibular gland lobule. The secretory portions are composed ofpyramidal serous (light blue) and mucous (light brown) cells. Serous cells are typical protein-secreting cells, with rounded nuclei, accumulation of rough ER in the basal third, and an apex filled with protein-rich secretory granules. The nuclei of mucous cells, flattened with condensed chromatin, are located near the bases of the cells. The short intercalated ducts are lined with cuboidal epithelium. Thestriated ducts are composed of columnar cells with characteristics of ion-transporting cells: basal membrane invaginations with mitochondrial accumulations. Myoepithelial cells are shown in the serous acini.

Figure 16–3.

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Parotid gland. The large...