Salivary glands

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
Serous
• 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. Parotid Gland

37. Parotid Gland

38. Intra-glandular adipose tissue in
parotid gland

39. Submandibular Gland

40. Submandibular Gland

41. Mixed Salivary Gland

43. Mucous Acini

45. Sublingual-purely mucous gland

46. Sublingual

47. Minor salivary glands of Palate
• Aggregations of Mucous
acini
• No striated duct

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

49. 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.

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

51. 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

52. 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

53. MCQ
Sebaceous gland is an example of
• Holocrine gland
• Apocrine gland
• Merocrine gland
• Unicellular gland

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

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