Salivary Glands Histology PDF

Histology of the Salivary glands Prof. Dr. Heba Fathy Ass. Prof. of Histology and cell biology Salivary glands are generally categorized under two groups: A. The Main Salivary Glands: Three pairs. Large compound tubulo- alveolar glands. Secrete their products...

Histology of the Salivary glands Prof. Dr. Heba Fathy Ass. Prof. of Histology and cell biology Salivary glands are generally categorized under two groups: A. The Main Salivary Glands: Three pairs. Large compound tubulo- alveolar glands. Secrete their products via a branched system of ducts. They form >90% of total daily salivary output. Regulated by local and central nervous reflexes. They include the parotids, the sublingual and the submandibular glands.  B- Minor salivary glands Buccal, labial, lingual and palatine. Small. Simple tubuloalveolar glands. Scattered in the oral cavity. Secret continuously. Loading… Moisten and lubricate the oral cavity.  THE GENERAL ARCHITECTURE OF THE MAIN SALIVARY GLANDS 1-The Stroma: a. The capsule: covers the gland and separates it from the surrounding structures and conveys its vascular and nervous supply. b. Septa (trabecula): arise from the capsule and divide the gland into lobes and lobules c. Reticular stroma: a network support the secretory units and ducts of the gland. 2- The Parenchyma: A- The Secretory Units: An acinus: group of secretory cells surrounding a lumen and resting on a basement membrane, surrounded by : Basket cells or myoepithelial cells: Modified epithelial cells that separate acinar cells from the basal lamina. Loading…  Contain abundant actin and myosin filaments to squeeze the acinar secretion into the duct. They are also located along the beginings of the ducts.  According to the nature of secretion and the predominant type of cells of the acini, there are: 1. Serous acini: They produce watery secretion rich in salts and digestive enzymes. 2. Mucous acini: They secrete mucus (viscid glycoproteins). Serous acinus Mucous acinus Rounded Oval Shape Smaller Larger Diameter Narrower Wider Lumen Pyramidal Cuboidal Shape of the cells Deeply stained : apical Vacuolated pale H& E staining acidophilia (secretory granules)& basal basophilia (rER) Spherical (nearer to the base) Flattened Nuclei of the and basal cells Less numerous More numerous Basket cells and complicated  c. Mixed acini (mucoserous acini): Mucous acini surrounded by a deeply stained caps of serous cells called the serous demilunes. Mainly present in the submandibular gland.  B- The Duct System: (conducts and modify saliva) 1- The intercalary ducts: Thin walled, lined by low cuboidal cells. Drain the secretory units directly. Loading… B-The Secretory Striated Ducts: Relatively large, eosinophilic rounded or oval structures with a wide lumen. Lined by cuboidal or low columnar cells with indistinct boundaries. The cells have central rounded nuclei and eosinophilic striated cytoplasm. Ultrastructurally, the basal cell membrane forms deep infoldings lodging many regularly arranged mitochondria, which are responsible for the striated appearance of the cells (for cellular active ion transport). - These ducts are concerned with modification of composition of saliva (by active ion pump making the saliva hypotonic solution). Intralobular ducts 3. The Interlobular Ducts: Found within the interlobular connective tissue septa between the lobules. Lined by simple columnar epithelium.  4. The Interlobar Ducts: Larger ducts formed by the union of the interlobular ducts. Present in the interlobar septa between the lobes. Lined by pseudostratified columnar epithelium.  5. The Main Duct It is formed by union of the interlobar ducts. Lined by non keratinized stratified squamous epithelium (same lining of the oral cavity). Look at the diagram & answer the following labels 1- Serous acinus. 2- Mixed seromucous acinus. 3- Serous cap cells of mixed acinus( serous demilunes). 4- Secretory striated duct. 5- Mucous acinus.  THE PAROTID GLAND The capsule and septa are thick and well developed. THE PAROTID Large number of fat cells within the septa as well as between the secretory acini. GLAND  The secretory acini are exclusively serous (high amylase activity). The intralobular ducts are prominent; they are formed of equally long intercalated and striated secretory segments.  THE SUBMANDIBULAR GLAND The capsule and septa are moderately thick.  Fat cells are present between the acini but less numerous than in the parotid gland.  The secretory acini are mainly of the serous types (80%) and only about 20% are of the mixed type.  The striated secretory ducts are more prominent. They form about 80% of the length of the intralobular ducts.  THE SUBMANDIBULAR GLAND Fat cells Serous acini Mixed acini  THE SUBLINGUAL GLAND The capsule is thin but the septa are thick  THE The secretory SUBLINGUAL acini are mainly of the mucousGLAND type (99%). The remaining 1% is represented by mixed acini. Loading… The intralobular ducts are very short and poorly developed. They Mucous acini are formed mainly of the striated Secretory striated secretory segment. ducts THE SUBLINGUAL GLAND Histological differences between salivary glands Parotid Submandibular Sublingual Capsule and septa Thick and well developed Moderately thick capsule The capsule is thin but the septa. and septa. septa are thick and well developed. Fat cells Large number Less numerous No fat cells Secretory acini 100% serous. serous types (80%) and mucous type (99%). The only about 20% are of the remaining 1% is the serous mixed type. cells forming the mixed acini. Myoepithelial cells Few myoepithelial cells Moderate no. of Numerous myoepithelial myoepithelial cells. cells Intralobular ducts Long, 50% intercalated: Moderately long, secretory They are very short, 50% secretory straited striated ducts form about formed 99% secretory 80% of the length of the striated segment. intralobular ducts.