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sublingual salivary gland histology slide

sublingual gland histology slide  - click to enlarge

GENERAL STRUCTURE OF SALIVARY GLANDS: All the salivary glands have a similar
microscopic structure except with few differences. Each major salivary gland consists of stroma, parenchyma and ducts.
I. Parenchyma: It is composed of alveoli (acini). An acinus resembles to a grape attached to its stem. The stem corresponds to duct system. Some parts of the ducts of the gland are also involved In secretory process so these glands are called compound tubulo- aiveoiar variety of glands. The alveoli are spherical consisting of: (a) epithelial cells arranged around a central cavity which continues into that of duct draining the alveolus; (b) basket cells and: (c) basement membrane.
a. Three types of alveoli are found
1.     Serous Alveoli: These are lined by serous cells, which are pyramidal (high cuboldal) In shape with spherical nucleus located in the basal half of cells. Apex of each cell contains zymogen granules and appears acidophilic. The base of each cell appears basophilic due to presence of rich rough endoplasmic reticulum. Serous cells have very fine spaces between them, which are called intercellular canallcull. Star shaped myoepithelial cells are also present between serous cells and basement membrane. Only serous acini are found in parotid and Von-Ebner salivary glands.
2.    Mucous Alveoli: These are lined by mucous cells which are pyramidal in shape but their nuclei are smaller, darker and flattened lying against basal plasmalemma. Apical region contains muclnogen granules, which appear pale and foamy. The mucous alveoli do not show intercellular canallcull. Tfiese possess myoepithelial cells. Mucous cells are organized as tubules like cylindrical arrays of cells around a lumen.
3.    Seromucous Alveoli: Mucus cells form tubules but their ends are capped by a group of serous cells known a^ serous demilunes (crescents of Glanuzzl), which give a crescent shaped appearance in section. The demilune cells produce lysozyme. The secretion of serous cells is discharged through intercellular canaliculi, which lie between adjacent mucous cells. These are typically seen in submandibular gland.

The parotid gland contains only serous acini while submandibular and sublingual glands contain serous, mucous and mucoserous acini.
b.    Myoeplthellal/Basket cells: These are stellate or basket or spindle-shaped cells
with multiple processes and single central nucleus. These are present within the basal lamina.
c.   The basement membrane is PAS+ve mucopoiysacharide layer around the alveolus and is surrounded by stroma of gland.
serous acinus
Mucous acinus
Size of acinus (diameter)
Lumen of acinus
Number of cells/acinus
> 8
size of cell
High cuboidal (pyramidal) or columnar
Cuboidal or iow columnar
Cell's lateral boundaries (due to secretory canallcull at cell boundaries)
Not clear (due to many canaliculi)
Clear (due to less canaliculi)
Shape of nucleus
Flattened or oval (but when empty, the nucleus is rounded)
Position of nucleus
Basal striations In cytoplasm
Less basophilic (rich in glycoproteins and appears vacuolated due to removal of dissolved mucous)
Supranuclear cytoplasm
Many zymogen granules (electron- dense)
Many more mucinogen granules (electron-lucent)
Basket cells and less in number
Spindle-shaped cells and more in number
Serous fluid (watery) rich in enzymes
Mucous fluid (thick or viscid) rich in glycoproteins
Apical microvilli
Present but Irregular
Amylase activity
comparison Between various Types of Acini

II.       Stroma (C.T. framework): Major salivary glands are surrounded by dense collagenous connective tissue capsule from which septa (trabeculae and C.T. framework) arise and divide the gland into lobes and lobules. These septa contain blood vessels and ducts. The stroma is formed of C.T. cells (mainly fibrocytes and fat cells) and fibres (mainly collagen). Many plasma cells and lymphocytes are also seen in stroma of parotid gland.

III.    Duct System: The ducts of secretory acini (secretory eye-pieces) open into Intercalated or Intercalary ducts. The intercalary ducts are lined by simple low
cuboldal epithelium and are connected to intralobular ducts. The intralobular ducts are known as striated secretory ducts because of basal radial striations of their cells (because of basal plasmalemmal infoidings and richness of mitochondria). The Intralobular ducts are lined by simple columnar epithelium and have secretory function. The secretory eyepieces, intercalary ducts and intralobular ducts are present within the lobules. The intralobular ducts drain Into Interlobular ducts, which are lined by simple columnar epithelium and are located in the C.T. septa between the lobules of gland. These unite to form the Interlobar or excretory ducts. The interlobar ducts are present in the C.T. septa between the lobes and are lined by stratified cuboldal or stratified columnar epithelium. The epithelium remains stratified columnar in main duct but changes to non-keratlnlzed stratified squamous near its orifice.
Only serous (rarely a mucous acinus may be found)
Mixed (serous > mucous) with many serous demilunes
Only mucous with less serous demilunes (pure serous acini absent)
Thick & well developed
Very thin or absent
Plasma cells and lymphocytes In stroma
intercalated duct
Long & prominent
Variable but usually Long & narrow
Short & less prominent
Striated duct
Wider & longer
Almost absent but rarely present (short & less prominent) due to less or no basal striations
secretion (viscosity)
Serous (watery) PAS+
Mucous (thick or viscid)
Amylase activity In secretion
Lysozyme activity In secretion (due to serous demilunes)
Contribution to saliva
Comparison Between Various Major salivary Glands

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