Salivary Glands
Are exocrine gland, they empty their secretion into the oral cavity by their ducts. Classified into minor and major. These glands may contain serous cells or mucus-secreting cells or mixture of both.Minor salivary glands
found mainly in the sub mucosa of the mouth, empty their secretions into the mouth by short ducts, they are named according to their locations (buccal, labial, palatine, lingual and tonsilar).
All are characterized by:-
No capsule
Branched, tubular, acinar in type
No intercalated duct
Secrete saliva continuously to keep the mucous membrane of the mouth moist.
Major salivary glands:
3 large pairs of gland: Parotid, Submandibular, Sublingual.
Also called extrinsic salivary glands located outside the oral cavity, have long ducts leading to the mouth, they secrete the saliva upon non continuous stimulation, they respond to various stimulation like the presence of food in the mouth, smelling or seeing the food, the saliva represents the secretion of all the salivary glands about one and half liter per day, 90% water and contains important enzymes of different concentrations also IgA for killing the bacteria.
Parotid gland
They are largest pair of salivary gland situated below and in front of pinna on each side of the face they are flat and well- capsulated. The duct of the gland open into the mouth opposite to the upper second molar teeth.Histologically: Parotid gland surrounded by fibrous tissue capsule from which fibrous septa dividing the gland into lobes and each lobe is subdivided into many lobules, one of the characteristic feature of the gland is the presence of adipose tissue, each lobule composed of branched tubulo alveolar acini of serous type, purely secrete serous fluid. Serous cells are cubidal or pyramidal surrounding small lumen, have spherical centrally located nucleus, luminal surface of the cell cytoplasm contain zymogen granules that stain purple by using H& E stain while RER found at the basal part of the cytoplasm, the duct within the lobule called intralobular consist of intercalated and striated duct.
The intercalated duct lined with low cuboidal epithelium, striated duct lined by tall columnar epithelium showing vertical striation which is produced by large number of rod- shaped mitochondria. They leads to interlobular ducts which run in the interlobular septum then they unite to form the main excretory duct that empty into the oral cavity.
Submandibular gland
The gland lie on each side of the neck just below the mandible, their duct open into the floor of the mouth on each side of the frenulum of the tongue just behind the lower incisor teeth. The gland is surrounded by fibrous capsule and from which fibrous septa divide the gland into lobes and lobules, no adipose tissue. The secretory part composed of tubulo- alveolar acini of serous and mucous type but majority are serous alveoli.
Mucous alveoli :
Mucous cells are polyhedral.
Surrounding large lumen.
Pale- staining cytoplasm.
Flat nucleus lie at the base of the cell (eccentric).
Clear boundries between the cells.
Serous alveoli :
Serous cells are cuboidal or pyramidal.
Surrounding narrow lumen.
Dark cytoplasm filled with zymogen granules.
Boundaries between the cells are not clear
In the sub mandibular gland the serous acini arranged as a crescent or demilune outside the end of mucous alveoli called serous demilune.
The duct system : secretory acini empty into the intercalated ducts lined by dark stained cuboidal epithelium, they merge to form striated ducts lined by tall columnar light stained cells with ertical striation which fuse to form larger interlobular duct (lined by pseudostratified epithelium), the inter lobular ducts join to form the major duct lined by stratified epithelium.
Intercalated duct
Cuboidal
Dark staining
No striation
Striated duct
Tall columnar
Pale staining
Striated basal cytoplasm
Sublingual gland
2 glands lie in the floor of the mouth on either side of the frenulum of the tongue, it is the smallest gland, no capsule and the gland is divided into many lobes which differ in size, contain mainly mucous acini some of which show serous demilune.
The duct system show intralobular ducts (lacking the striated or inter calated appearance) &interlobular ducts all drain into a single large excretory duct open in the mouth near to or with submandibular duct.