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Histology of Salivary Glands

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1 Histology of Salivary Glands



4 What is a gland? Gland is an organ of secretion made up of specialized secretory cells derived from the surface epithelium on which it opens.

5 General Features Epithelial in origin
Present as discrete organs or in layers. Secretory cells form functional units called secretory end pieces- may be flask (Acinus)or cylindrical (Tubular)shaped

6 Types of Secretory units

7 General Features Fluid secreted may be enzymes, hormones or mucus.
Secretion is modulated by nervous and hormonal influences. Myoepithelial cells- star shaped, contractile, lie between the secretory cells and the basement membrane

8 Mixed Salivary Gland

9 Development Develop as invagination of the epithelium into the underlying vascular connective tissue. Distal part forms glandular or Secretory end Piece – functionally an active portion. Proximal part-Excretory Duct-opens on the surface of the epithelium Some cells get detached from the epithelial surface- Ductless or endocrine glands

10 Development of Gland

11 Glandular Epithelium




15 Classification of Glands
Based on the site of Secretion Exocrine Gland Endocrine Gland Paracrine Gland- secretes its products into the local extracellular space affecting the surrounding cells e.g. enteroendocrine cells of gastrointestinal tract (GIT)


17 Classification of Glands
Based on the Number of cells Unicellular Gland- goblet cells in the respiratory and intestinal tracts Multicellular Gland- all glands other than goblet cells

18 Classification of Glands
Based on the Number of Ducts and the shape of secretory end piece Simple Gland- one duct Compound Gland- has minor and major ducts Both the types are further subdivided into Tubulo, Alveolar/Acinar or Tubulo-alveolar/acinous


20 Multicellular Glands

21 Compound Tubulo-alveolar

22 Compound Tubulo-alveolar

23 Compound Glands Simple Alveolar-Penile urethra
Simple Branched alveolar-Sebaceous gland Compound Alveolar- Pancreas, Parotid, Mammary gland and glands of Respiratory tract. Simple Tubular-Crypts of Leiberkuhn Simple branched tubular-Uterine glands,Pyloric and fundic glands Compound Tubular-Brunner’s Gland, Cardiac glands Simple coiled tubular-Sweat gland Compound Tubulo-alveolar- Submandibular & Sublingual salivary glands

24 Mixed Salivary Gland

25 Classification of Glands
Based on the Mode of Secretion Merocrine Gland- No loss of Cytoplasm-e.g. most of the compound glands e.g. Pancreas Also known as Eccrine or Epicrine Apocrine Gland- Partial loss of cytoplasm-e.g. lactating mammary gland, sweat glands in the axilla and external genitalia Holocrine Gland- Complete loss of cytoplasm e.g. sebaceous and tarsal gland Cytocrine Gland- Cells are released as secretion. e.g. Testis (spermatozoa)

26 Modes of Secretion

27 Classification of Glands
Based on the Nature of Secretion Serous Gland- thin, watery secretion rich in enzymes e.g. Parotid gland Mucous Gland- thick, viscous secretion for protection and lubrication. e.g. Sublingual salivary gland Mixed Gland (seromucous)- both watery and viscous material.e.g. Submandibular salivary gland

28 Difference between Serous & Mucous Acini
Thin, watery Proteinaceous secretion Zymogen granules in cyto Central rounded Nucleus Small Lumen Indistinct cell bondaries Darkly stained Enzymatic action Parotid Gland Mucous Thick, viscous Mucopolysaccharides Mucigen droplets Nucleus-flat & peripheral Large Lumen Distinct cell boundaries Lighly stained Protection & lubrication Sublingual gland

29 Mixed salivary gland Serous Acini Mucous Acini
Seromucous Acini- having Serous demilunes



32 General Architecture of a Compound Gland
Gland may be divided into lobes and lobules. Parenchyma- Secretory end pieces- Acini/tubules /tubulo-acinar) Ducts- Intralobular, interlobular, main excretory duct Stroma Capsule Septa (interlobular, interlobar) Loose intralobular connective tissue supporting the parenchyma

33 Clinical ADENOMA: Benign tumors arising in the gland
ADENOCARCINOMA: Malignant growth in the gland


35 Serous Acinus

36 Ducts


38 Striated Duct Larger than the acinus Eosinophilic columnar cells
Central nuclei Vertical Cytoplasmic stiations due to foldings in the basal plasma membranes

39 Parotid Gland


41 Parotid Gland

42 Intra-glandular adipose tissue in parotid gland

43 Submandibular Gland

44 Submandibular Gland

45 Mixed Salivary Gland


47 Mucous Acini


49 Sublingual-purely mucous gland

50 Sublingual

51 Minor salivary glands of Palate
Aggregations of Mucous acini No striated duct

52 Minor salivary glands of Palate(High Power)
Mucous acini with central Lumen Large Pyramidal cells with granular cytoplasm Nucleus towards the basement membrane

53 The minor salivary glands are small aggregates of unencapsulated mucous or serous glands. In the tongue they are in intimate contact with the striated muscle tissue.

54 Keratin cocktail stains intercalated, striated and interlobular ducts, but acinar and myoepithelial cells are mostly negative.

55 MCQ The serous gland can be identified by the presence of serous acinus with A) Small Lumen B)Large Lumen C)Flat peripheral Nuclei D)Mucigen droplets

56 MCQ When there is a complete loss of cytoplasm resulting in cell death of the secretory cell during the process of secretion, the gland is said to be A) Merocrine B) Apocrine C) Holocrine D) Cytocrine

57 MCQ Sebaceous gland is an example of Holocrine gland Apocrine gland
Merocrine gland Unicellular gland

58 MCQ Mucous Acinus A) Secretes thin watery fluid
B) Has flat, peripheral nucleus C) Has a small lumen D) Contains zymogen granules

59 MCQ Sweat glands in the axilla are an example of A) Merocrine gland
B) Apocrine gland C) Holocrine gland D) Cytocrine gland

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