HISTOLOGY OF SALIVARY GLANDS..pptxpresentaion

Parotid gland
Sublingual gland
Submandibular gland

1. HISTOLOGY OF SALIVARY GLANDS

2. Introduction Salivary glands secrete saliva in the oral cavity. Salivary glands include: • Major salivary glands - parotid, submandibular, and sublingual glands • Minor salivary glands : -located in lamina propria of lips, cheeks, soft palate, and tongue. • Each salivary gland has duct and secretory acini

3. Histology of salivary glands Salivary gland consists of a highly branched duct system and a well developed secretory acinar unit • Acini are made up of pyramidal cells. • Based on the nature of secretory cells , acini are classified as serous acini, mucous acini, and mixed acini. • Glandular tissue is surrounded by connective tissue capsule. • Septa arising from the capsule divide the gland into a number of lobes and lobules.

4. Salivary ducts Main salivary duct of the gland divides to form • lobar • interlobular and • intralobular (striated and intercalated) ducts

5. Salivary ducts Intercalated duct • These are lined by low cuboidal epithelium. • These ducts connect secretory acini with larger ducts. • These are predominant in serous glands. Striated ducts • These ducts connect intercalated ducts with interlobular ducts • These are lined by simple columnar epithelium. • Basal portion of these epithelial cells shows numerous infoldings of the plasma membrane. It helps in the accommodation of numerous mitochondria and increasing surface area. • On H&E staining, basal infoldings give striated appearance; hence, called striated duct. • Striated ducts are predominantly present in serous glands. • Striated ducts are absent in mucous glands

6. Excretory ducts They include interlobular, lobar, and main excretory ducts. • These duct shows the gradual epithelial transformation from simple columnar to stratified cuboidal or columnar epithelium. • Main excretory ducts open into the oral cavity.

7. Secretory acini Salivary glands are tubuloalveolar glands salivary glands have serous, mucous, and mixed acini. Serous acinus • Serous acini secrete protein-rich, watery secretions. • These acini are lined by pyramidal-shaped simple columnar epithelium. Serous cells have • Rounded basal nucleus • Large amount of rough endoplasmic reticulum that gives basal basophilia Well-developed Golgi complex and secretory vesicles that give apical eosinophilia

8. Mucous acinus Mucous acini secrete thick mucoid secretions. • These acini are lined by pyramidal-shaped simple columnar epithelium. Mucous cells have • Flat, elongated, and basally placed nucleus • Foamy cytoplasm (mucus removed during tissue processing) •Mucous acini have wider lumen than serous acini

9. Mixed acini Mixed acini secrete both mucus and enzyme-rich watery secretions. • Mixed gland has mucous acini with serous demilunes. • Mixed acini are lined by mucous cells and these cells are capped by demilune of serous cells. All serous cells open into the lumen of the acinus by fine canaliculi.

10. Myoepithelial cells These are also called basket cells or myoepithelium. • These are star-shaped cells that are present between the epithelium and basal lamina of acinus. • They have actin filaments in their cytoplasm. • Their contractions help the acini to expel the secretions

11. Parotid gland Parotid gland is the largest salivary gland. • It is covered by thick capsule and divided into number of lobes and lobules • Main secretory duct/Stenson's duct opens into the vestibule of mouth opposite to the upper second molar tooth. • Acini: Parotid gland mainly consists of serous acini. These acini are surrounded by myoepithelial cells. • Ducts: Parotid gland has number of intralobular (intercalated and striated) ducts, and interlobular and lobar ducts. • Intercalated ducts are lined by low cuboidal epithelium. • Striated ducts are lined by simple columnar epithelium with basal infoldings. • Other ducts are lined by stratified cuboidal to stratified squamous epithelium. • In between acini, adipose tissue is also present.

12. Submandibular gland Submandibular gland is a mixed salivary gland. The submandibular duct (Wharton’s duct) open into oral cavity on the sublingual papilla at the side of the frenulum of the tongue • It has a well-defined capsule. Septa arising from capsule divide the gland into number of lobes and lobules. • Acini: Gland shows presence of both serous and mucous acini. Few mucous acini also show serous demilunes. • Ducts: Gland has lobar, interlobular, and intralobular (striated and intercalated) ducts.

13. Sublingual gland These are small masses of glandular tissue that lie in the substance of the tongue. • Sublingual gland is not surrounded by well- defined capsule • Acini: Sublingual gland predominantly has mucous acini. Few serous and seromucous acini are also present. • Mucous secretory units are tubular (not purely acinar). • Ducts: Sublingual glands do not have intercalated duct (rarely present) and striated ducts are also very few. Interlobular and lobar ducts are present.