Classification of glands. Detailed microscopic structure of exocrine glands. differences between serous and mucus acini. Microscopic structure of Parotid, submandibular and sublingual glands.

1. Glands

2. Competencies
• AN70.1 - Identify exocrine gland under the microscope
& distinguish between serous, mucous and mixed acini
• AN52.1 Describe & identify the microanatomical
features of ……. Suprarenal gland

4. Objectives
• Introduction of Glands
• General Features
• Development
• Classifications
• Examples
• Applied

5. Gland - Introduction
• Some epithelial cells converted in to specialized
cells to perform a secretory function - form glands
• Definition:
An organ of secretion made up of specialized
secretory cells; derived from surface epithelium
on which it opens

6. General Features of Glands
• Can be present as “Discrete Organ” or “ in the
layers of viscera”
• Epithelial in origin (Derived from surface
epithelium)
• Functional unit of gland is formed by specialized
secretory cells known as – Secretory End Piece
• Fluid secreted by glands contain enzymes, mucus,
hormones, protein, fat etc…

7. General Features of Glands
• Rate of secretion is modulated by Nervous &
Hormonal influence
• Secretory end piece of some exocrine glands is
surrounded by star shaped contractile cells that lies
between cells & basement membrane
–Called Myo-epithelial cells
–Share features of both
epithelium & muscle cell
–Help in expulsion of
secretions

8. Glandular Epithelium

9. Development of Glands
Developed as cords of
epithelial cells from the
surface of membrane
Invaginates in to underlying
Connective tissue &
Form 2 parts
Proximal
Part
Distal Part

10. Development of Glands
Form duct
Connect secretory end piece
with surface of epithelium
Proximal Part
Distal Part
Exocrine Glands
Differentiated in to
the secretory cells
Secretory End Piece
Pours the secretion through ducts / directly on
surface of the glands or epithelium

11. Development of Glands
DisappearProximal Part
Distal Part
Endocrine Glands
Form islands of the secretory
cells permeated / surrounded
by the blood capillaries
Pours their secretion in to directly in to blood
through the blood capillaries
Ductless Gland *

12. Based on Site of Secretion
Exocrine
With Ducts
Endocrine
Ductless
Exocrine +
Endocrine
Paracrine
Classification of Glands
Unicellular /
Multicellular
Cord & Clump type/
Follicular Type
Pancreas &
Liver
APUD &
DNES
APUD – Amine Precursor Uptake & Decarboxylation
DNES - Diffuse NeuroEndocrine System

13. Classifications of Exocrine Glands
Based on numbers of cell
Unicellular Multicellular
Goblet Cell

14. Multicellular Exocrine Glands
1. Based on branching pattern of ducts
Simple
No Branching
Compound
Branched

15. Multicellular Exocrine Glands
2. Based on Shape of Secretory End Piece
Tubular Alveolar /
Acinar
Tubulo-
alveolar

16. Multicellular Exocrine Glands
3. Based on Nature of Secretion
Mucous Serous Mixed /
Sero-mucous

17. Multicellular Exocrine Glands
4. Based on Manner of Secretion
Merocrine Apocrine Holocrine Cytocrine

18. Multicellular Exocrine Glands
5. Based on Development of gland
Ectodermal Endodermal Mesodermal

19. Exocrine glands
Based on number of ducts
• Simple(single duct)
• Compound(minor & major ducts)
Based on shape of secretory piece:
• Simple tubular/ alveolar
• Simple branched tubular/ alveolar
• Simple coiled tubular
• Compound tubular/ acinar
• Compound tubulo-alveolar / acinar

20. • Simple:
– Secretion poured to surface by
un-branched duct
• Compound:
– Duct divides in to branches to form
elaborated / complex duct system;
– Each smaller terminal duct receive
secretion from it’s own secretory end
piece
– These ducts unite to form larger
ducts which finally drain on to surface
Based on Number of Ducts:

21. • Tubular: (Simple / Compound)
– Secretory end piece is like tubule
– Straight, branched or coiled
Based on Shape of Secretory End Piece:
Simple
Straight
Intestinal Crypts
Simple
Coiled
Sweat Gland
Simple Branched
Uterine gland
Fundic & pyloric
glands of stomach
Compound
Cardiac glands
of stomach &
Brunner’s gland
of duodenum

22. • Alveolar: (Simple / Compound)
– Secretory end piece Flask shaped
with large lumen
– Un-branched or branched
Simple
Un-branched
Urethral Glands
Simple Branched
Sebaceous &
Tarsal Glands
Compound
Mammary gland betn
puberty & 1st Pregnancy
Based on Shape of Secretory End Piece:

23. • Acinar: (Mostly Compound)
– Secretory end piece Round shaped
with small lumen
– Mostly branched
Compound Acinar
Pancreas
Parotid
Based on Shape of Secretory End Piece:

24. • Tubulo – Alveolar / Acinar:
– Combination of both Tubular &
alveolar / Acinar
– Mostly branched
Compound
Tubulo – Alveolar / Acinar
Sublingual gland
Submandibular gland
Lactating mammary gland
Based on Shape of Secretory End Piece:

25. Simple Glands

26. Compound Glands

27. According to Mode of secretion:
• Merocrine
• Apocrine
• Holocrine
• Cytocrine
Exocrine glands

28. • Merocrine:
– A.K.A.: Eccrine / Epicrine
– Secretion discharged through intact
cell membrane
– By Exocytosis
– No loss of cytoplasm
Based on Mode of Secretion:
E.G.
Protein content of mammary gland
Parotid
Pancreas
Typical & Atypical sweat glands

29. Merocrine
Exocytosis
Exocrine glands

30. • Apocrine:
– Apical portion (luminal) of cell
disintegrate to discharge its secretion
– Nucleus & basal portion remain intact
from which cell can regenerate
– Partial loss of cytoplasm
Based on Mode of Secretion:
E.G.
Lipid content of mammary gland
Ceruminous gland of Ear
Moll’s Gland in Eyelid
Modified Sweat
gland

31. Exocrine glands
Apocrine

32. • Holocrine:
– Entire cell disintegrate to discharge
its secretion
– Result in death of cell
– Complete loss of cytoplasm
Based on Mode of Secretion:
E.G.
Sebaceous gland
Tarsal Glands in Eyelid

33. Exocrine glands
Holocrine

34. • Cytocrine:
– Cell are released
as secretion
Based on Mode of Secretion:
E.G.
Spermatozoa from Testis
Ovum from Ovary
Bone Marrow

35. Exocrine glands
Cytocrine

36. Exocrine glands
Cytocrine

37. According to Nature of secretion:
• Serous
• Mucous
• Mixed
Exocrine glands
Mucous Serous Mixed

38. Serous
Thin, watery
Proteinaceous
Zymogen granules
Central rounded
Small Lumen
Indistinct
Darkly stained
Enzymatic action
Parotid Gland
Mucous
Thick, viscous
Mucopolysaccharides
Mucinogen droplets
Flat & peripheral
Large Lumen
Distinct
Lighly stained
Protection & lubrication
Sublingual gland
Consistency
Content
Cytoplasm
Nucleus
Lumen
Cell boundaries
H&E Staining
Function
Examples

39. Serous Acinus / Gland
• Secretion: Thin, watery,
– Rich in enzymes, protein in nature
• Cells: Pyramidal & Small with
Indistinct boundaries
• Cytoplasm: Granular (Zymogen)
– Rich in rER
– Stain darkly with H/E stain
• Nuclei: rounded & basal / central
• Size of lumen: Small
• Function: Enzymatic
• E.G.: Parotid & Lacrimal glands

40. • Secretion: Thick Viscous
– Which collects in the apical part
• Cells: Low Columnar & Large with
distinct boundaries
• Cytoplasm: Mucinogen droplets
– Stain very lightly with H/E stain &
– Looks empty
• Nuclei: Flattened & basal
(mucoid pushes nuclei towards base)
• Size of lumen: Large
• Function: Protection & Lubrication
• E.G.: Sublingual glands
Mucous Acinus / Gland

41. • Contain both serous & mucous
secretory units
• Sometimes serous cells form
crescentic caps on mucous acini
called as Serous Demilunes
Mixed Acinus / Gland

42. Serous Acini Mucous Acini

43. Serous Acini Mucous Acini

44. Salivary Glands

45. • Exocrine: with Ducts / Externally secretory gland
• Secrete its products on to the surface through it’s duct
• Produce saliva and pour their secretion in the oral cavity
• Contain water, mucus, proteins, salts, salivary
amylase(ptyalin) and IgA
• Functions:
• Moisten food
• Lubricate & moisten oral cavity
• Initiate digestion of carbohydrates
Salivary Glands

46. Two types:
• Major (paired)
• Parotid
• Submandibular
• Sublingual
• Minor
• Lingual in tongue
• Palatine in palate &
tonsil
• Labial in lips and
• Buccal in cheeks
Salivary Glands

48. • Consist of 3 components
– Secretory end piece
– Duct System
– Supporting Connective
tissues
Salivary Glands
Parenchyma
Stroma
Parenchyma

49. Structural Organization of Salivary Glands
Lobes
Lobules
Blood Vessels & Nerves
Parenchyma Stroma
Inter-lobar
Septa
Capsule
Ducts
Inter-lobular Septa

50. General Architecture of a Salivary Glands
• Parenchyma-
– Secretory part- Acini / tubules / tubulo-acinar
– Conducting part: Ducts- Intralobular, interlobular, main
excretory duct
• Stroma-
– Capsule
– Septa (interlobular, interlobar)
– Loose inter-lobular connective tissue supporting the
parenchyma
– Divide the gland into lobes and lobules.

51. Salivary Glands :- Parenchyma - Secretory part
• Compound tubulo-alveolar
glands – Racemose gland
• Blind sac composed of
secretory cells
• Acini / tubules / tubulo-
acinar
• Based on nature of secretion
3 Types:
– Serous
– Mucous
– Mixed

52. Salivary Glands:- Parenchyma -Conducting part
Secretory Acinus
Intercalated ducts
Low cuboidal / Squamous epithelium
Secrete HCO3 ¯ &
Absorb Cl ¯
Prominent in serous glands

53. Parenchyma - Conducting part
Secretory Acinus
Intercalated duct
Simple Columnar epithelium
Regulates of water and
electrolyte contents of saliva
Presence of basal striation
Striated duct

54. Cell of Striated Duct
Infoldings of basal plasma
membrane
Occupied by mitochondria
Basal Striation

55. Parenchyma - Conducting part
Secretory Acinus
Intercalated duct
Simple columnar to
Pseudo-stratified Columnar
Striated duct
Inter-lobular duct
Stratified Columnar / cuboidal
Lobular & Main Excretory duct
Near opening Stratified squamous

56. Parenchyma - Conducting part
Low cuboidal /
Squamous
epithelium
Simple Columnar
epithelium
Stratified
Columnar
/ cuboidal

57. Intercalated duct
SD
Lu
Striated duct
Excretory duct

58. • Development of duct system of the salivary gland
depends on the nature of secretion
• Predominantly serous secreting gland: well
developed duct system
–Modification of secretion occurs
• Predominantly mucous secreting gland: poorly
developed duct system
–No modification of secretion
Parenchyma - Conducting part

59. Salivary Glands - Section
Large number of closely
packed acini with ducts
scattered between them
Supported by connective
tissue septa containing
blood vessels, lymphatics
and nerves
Homocrine &
Heterocrine ?

60. Salivary Glands
Both acini and ducts
surrounded by contractile cells
Myo-epithelial cells
• Star shaped / Basket
shaped around acini &
• Fusiform around ducts

62. Salivary Glands - Classification
• Parotid gland:
– Only serous acini
• Submandibular & sublingual:
– Submandibular:
• Predominantly serous secreting
• Serous + mucous + mixed acini
– Sublingual:
• Predominantly mucous secreting
• Mucous + mixed acini (Pure serous acini are rare)
Purely serous
Mixed glands

63. Parotid

64. Parotid

67. Serous
Submandibular Gland

68. Submandibular

71. Submandibular

74. Clinical
• ADENOMA: Benign tumors arising in the
gland
• ADENOCARCINOMA: Malignant growth in the
gland