Salivary Glands and Pancreas
I. Introduction
Salivary glands
§ involved in secretion of enzymes that aid in digestion
§ moistening of food.
Pancreas
§ secretes numerous enzymes which aid in digestion
§ plays major role in glucose regulation
II. Salivary Glands
§ Classified according to function, location, predominance of serous or mucous acini
§ Major salivary glands: parotid, submandibular (submaxillary), sublingual
§ Minor salivary glands: buccal, palatine, labial, lingual
Three types of salivary secretory units
§ Serous acini
Consists of pear shaped groups of epithelia cells surround by distinct basement membrane
Epithelial cells have dense cytoplasm and basal nucleus
Acini have a central lumen into which secretions flow from the epithelial cells
§ Mucous acini
Arger than serous acini
Secretory cells have an abundant cytoplasm filled with clear mucous
Epithelial cells are pyramidal with a flattened basal nuclei
§ Mixed acini
Characterized by a crescent shaped formation of serous cells capping a mucous acini (serous demilune) or mixed
pattern of serous and mucous acini
Former patter seen typically in submandibular gland
Morphology of major salivary glands
§ Characterized by three types of secretory units
§ In the parotid gland the intercalated duct is longer than the submaxillary and sublingual glands
§ In contrast, the striated duct is longer in the submaxillary gland
§ Sebaceous glands are more frequent in the parotid gland, in the sublingual gland
§ In the sublingual gland the intralobular ducts are inconspicuous
Gland structure
§ Consists of a CT stroma with blood vessels, nerves, lymphatics and ducts
§ CT septae divide the glands into lobules
§ Acini make up the parenchymal component
Duct system
§ Transports the saliva from the gland to the oral cavity and modifies its concentrations of electrolytes
§ Composed of different segments
§ First two segments, the intercalated and the striated ducts are intralobular; they are secretory ducts
§ The intercalated duct
the first segment and is lined with sqamous or low cuboidal epithelium
has an irregular layer of myoepithelial cells
§ Striated ducts
have a simple columnar epithelial lining
has characteristic striations on the basal side caused by membrane invaginations and mitochondria
this structure is involved in the transport of water and electrolytes
§ Interlobular ducts
located in the CT of the septae
lined with pseudostratified columnar epithelium along with sparse goblet cells
as diameter enlarges, the epithelium becomes a stratified columnar
as the duct enters the oral cavity, it s lined distally with nonkeratinized stratified sqamous epithelium
Major Salivary Glands
§ Paired structures
§ Parotid gland is of the serous type
§ Sublingual gland is of the mixed type & has a predominance of the mucous acini
§ Submandibular gland is of the mixed type & has a predominance of the serous acini
Myoepithelial Cells
§ Basket cells
§ Flat
§ Have long cytoplamic processes that aid in contraction
§ Lie between the epithelia cells and the basal lamina of acini
| Gland | Acini | Excretory Duct |
| Parotid | Serous | Stenson’s duct |
| Submandibualr | Mixed (serous predominate) | Wharton’s duct |
| Sublingual | Mixed (mucous) | Empty into floor of mouth |
III. Pancreas
§ In the adult the average pancreas s about 12-15 cm in length and weighs 60-140 g.
§ Pancreas has two separate components, exocrine and endocrine glands
§ Exocrine portion makes up approx 80% of organ and consists of numerous acini aggregated into lobules
§ Acini are separated by scant CT
General Histology
§ Pancreas has poorly defined capsule
§ Covered by thin areolar CT capsule
§ Capsule give rise to CT septae that divide the pancreas into lobules
§ Blood vessels, nerves, lymphatics and ducts transverse through the septae
§ Each lobule is supplied by a principal small artery
Acinar cells
§ Constitute the majority of the pancreas
§ Cells from rounded or elongated acini usually at the ends of the intercalated ducts
§ Normal acinar cells are large, pyramidal shaped cells with a single nucleus
§ Nucleus lies close to base of cells which rests on the basal laminae
§ Nucleus is round with clumped chromatin present
§ Apical portion of cell is filled with eosinphilic zymogen granules
§ Basal portion is strongly basophilic b/c cytoplasm is filled with RER
§ Cells secrete directly into acinar lumen through the apical surface
§ No myoepithelial cells are present
§ Merocrine secretion of proenzymes by acinar cells is regulated by secretin, cholecystokinin, and nerve stimulation from vagus
Ducts of the exocrine pancreas
§ The intercalated ducts are formed by low cuboidal epithelium & nucleus is ovid with inconspicucous nucleoli
§ The intralobular ducts lined by simple cuboidal epithelium & a single round nucleus appears to fill each cell
§ Interlobular ducts are larger and are lined by simple columnar epithelium & they are invested by a layer of collagenous tissue
§ Two major ducts are the Santorini and Wirsung; they have tall columnar epithelium with basal nuclei
Endocrine Pancreas
§ Constitutes 1-2% of adult pancreas
§ Endocrine cells form scattered aggregates that form the Islets of langerhans
§ Each islet is a lightly stained rounded group
§ A small amount of CT accompanies the large capillaries that run through each islet
§ Islet cells are not uniformly distributed in the pancreas
§ There are three major type cells type in the endocrine pancreas
| Cell type | Product | Relative amount |
| Alpha (A) | Glucagons | 15-20% |
| Beta (B) | Insulin | 60-70% |
| Delta (D) | Somatostatin | 5-10% |
Tags: acinar, CT septae, duct system, glucose regulation, intercalated duct, Interlobular duct, Mixed acini, Mucous acini, Myoepithelial Cells, pancreas, Paratid gland, parotid gland, salivary glands, Sebaceous glands, Serous acini, striated duct, sublingual gland, submandibular gland
