Special Histology and Embryology: Practical Manual - V. K. Napkhanyuk 2001

Digestive System
Anterior Segment of the Digestive System
Salivary Glands

Salivary glands (glandulae salivares) are exocrine glands that produce their secretion via a merocrine mechanism (without the destruction of secretory Cells).

Based on The Nature of the synthesized substance, all secretory Cells of the salivary glands are classified as protein, mucous, or mixed.

The ducts of three pairs of major salivary glands empty into the Oral Cavity: parotid, submandibular, and sublingual.

In addition, numerous minor salivary glands are located within the thickness of the oral mucosa: labial, buccal, lingual, and palatine.

The secretory products of all types of salivary glands collectively form saliva. Approximately 1.5 liters of saliva are produced per day.

Cytology/practical/97.html">Parotid salivary gland

The parotid salivary gland (glandula parotis) is a paired organ located in the parotid-masseteric region of the HEAD. It is a compound branched alveolar gland with a protein type of secretion.

Externally, the gland is covered by a Connective Tissue capsule, from which septa extend inward, dividing the gland parenchyma into lobes. The terminal secretory units consist of protein acini. Each acinus contains 10-15 serocytes. Serocytes are cone-shaped cells with basophilic Cytoplasm, a rounded Nucleus, and well-developed elements of the granular Endoplasmic reticulum and the Golgi complex. Myoepithelial cells are located at the periphery. Externally, the acinus is surrounded by a basal lamina. The excretory duct System of the parotid gland includes intercalated, striated, interlobular, and main excretory ducts.

Slide 5. Section of the human parotid salivary gland (Fig. 41).

Low magnification. Examine and draw the slide. At this magnification, it is clearly visible that the lobes have rounded margins and are separated by thick connective tissue septa containing Blood Vessels, nerves, and excretory ducts. Small ducts are lined with simple columnar epithelium, while large ones have Stratified Epithelium. The bulk of the lobes is formed by terminal units, whose rounded outlines in sections indicate their alveolar shape. The secretory serocytes of the terminal units are pyramidal in shape, and their nuclei are located somewhat away from The Cell base and are round. The cytoplasm of the gland cells varies in appearance depending on the phase of secretion. At the moment of release, it is filled with fine oxyphilic granules. In cells that have already released their secretion, the cytoplasm appears light. Between the terminal units within the lobes, oblique cross-sections of striated ducts can be seen, with striations visible in the basal regions of their cells.

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Fig. 41. Section of the human parotid salivary gland. Hematoxylin-eosin staining. x 280:

1 — terminal secretory units of the gland; 2 — excretory duct in interlobular connective tissue; 3 — blood vessel; 4 — myoepithelial basket cell; 5 — intralobular connective tissue

Label on the drawing: 1) terminal units of the gland; 2) salivary tube (striated duct); 3) excretory duct in interlobular connective tissue; 4) fat cell; 5) blood vessel; 6) myoepithelial basket cell; 7) intralobular connective tissue; 8) intercalated duct.

Submandibular salivary gland

The submandibular salivary gland (glandula submandibularis) is a compound alveolar-tubular branched gland with a protein-mucous type of secretion.

Externally, the gland is covered by a connective tissue capsule, from which septa extend inward, dividing the gland parenchyma into lobes.

The gland consists of terminal secretory units (acini) and a system of excretory ducts (micrographs 24, 25).

The terminal secretory units in the gland are of two types:

1) protein acini, consisting of 10-15 serocytes and peripherally located myoepithelial cells surrounded by a basal lamina;

2) mixed acini, consisting of mucocytes located centrally and surrounded peripherally by serocytes, which in turn are enclosed by a layer of myoepithelial cells and a basal lamina. The serocytes form so-called protein caps, or demilunes of Gianuzzi.

The excretory duct system consists of intercalated, striated, interlobular, and main excretory ducts.

Slide 6. Section of the submandibular gland (Fig. 42).

Low magnification. Examine and draw the slide.

Note that this is a mixed-type gland—protein-mucous—because groups of mixed (protein-mucous) terminal units are interspersed among the predominantly serous secretory terminal units. Intercalated ducts are poorly developed and are located only among purely protein terminal units. The slide clearly shows the distinction between serocytes and mucocytes. Serocytes possess basophilic cytoplasm. The nuclei of serocytes are round and located in the basal part of the cell. The apical portion contains acidophilic granules. Mucocytes (mucous cells) feature a dense nucleus pressed against the Base of the cell. The cytoplasm of mucocytes is very light and translucent.

Fig. 42. Section of the submandibular gland. Hematoxylin and eosin staining. x 280:

1 — serous secretory units; 2 — mixed secretory units; 3 — demilunes of Giannuzzi; 4 — mucous cells of the mixed secretory unit; 5 — intercalated duct; 6 — striated duct; 7 — myoepithelial cell; 8 — intralobular connective tissue; 9 — interlobular connective tissue; 10 — excretory duct

Label on the figure: 1) serous secretory units; 2) mixed secretory units; 3) demilunes of Giannuzzi; 4) mucous cells of the mixed secretory unit; 5) intercalated duct; 6) striated duct; 7) myoepithelial cell; 8) intralobular connective tissue; 9) interlobular connective tissue; 10) excretory duct.

Sublingual salivary gland

The sublingual salivary gland (glandula sublingualis) is a complex branched tubuloacinar gland with a mucoserous type of secretion, where mucous secretion predominates.

Unlike the submandibular and parotid glands, the connective tissue capsule is weakly developed. Intralobular and interlobular connective tissue septa are better developed in this gland than in the parotid and submandibular glands.

The terminal secretory units of the sublingual salivary gland are of three types: serous, mucous, and mixed.

Mixed acini make up the vast majority of the glandular parenchyma. In their Structure, they resemble the corresponding Structural components of the parotid and submandibular glands. However, the demilunes formed by seromucous cells are more prominent in this gland than in the submandibular gland. The cells forming the demilunes in the sublingual gland differ significantly from the corresponding cells in the parotid and submandibular glands. They react positively to mucin and simultaneously secrete both protein and mucus, which is why they are called seromucous cells.

The intralobular and interlobular excretory ducts of the sublingual gland are lined with a double-layered columnar epithelium, which transitions to stratified squamous epithelium near the orifice.

Slide 7. Section of the sublingual gland (Fig. 43).

High magnification. Examine and sketch the slide. Note that the sublingual gland is of a mixed type (mucoserous) with a predominance of mucous secretion. Purely serous terminal units are rare. There are numerous mixed and purely mucous terminal units. Intercalated ducts are practically invisible. Striated ducts are poorly developed; they are very short and rarely appear in cross-section. The intralobular and interlobular ducts are lined with Pseudostratified columnar epithelium. Connective tissue septa are more prominent.

Label on the figure: 1) loose connective tissue; 2) mucous secretory unit; 3) seromucous (mixed) secretory unit: a) mucous cells; b) serous cells (demilunes); 4) striated duct; 5) interlobular duct.