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