What is a Gland? An organised collection of secretory epithelial cells. Most glands are formed during development by proliferation of epithelial cells so that they project into the underlying connective tissue. Some glands retain their continuity with the surface via a duct and are known as EXOCRINE GLANDS. Other glands lose this direct continuity with the surface when their ducts degenerate during development. These glands are known as ENDOCRINE glands.

1. Dr Mathew Joseph MBBS, MD(AIIMS), BCC(Palliative Medicine)
Assistant Professor
Department of Anatomy
Amala Institute of Medical Sciences
Thrissur

2. Glands
 A gland is an organ that consists of specialized
secretory cells.
 Secreted material is usually a liquid.
 Epithelial in origin.
 Present in singly or in groups.
 Unicellular or Multicellular
 2 types:
Exocrine
Endocrine

3. Unicellular Glands
 Single cell distributed among non-secretory cells.

4. Multicellular Glands
 Formed by invagination of
epithelial layer in deeper
tissue to form a
diverticulum:
 Proximal part forms duct.
 Distal part forms secretory
element.

5. Exocrine: pour their
secretions onto an
epithelial surface,
directly or through
ducts.
Endocrine (ductless):
pour their secretions
directly into the blood.

6. Classification of Exocrine glands
 Based on shape & branching pattern of duct
 Based on mode of release of their product
 Based on the nature of their secretion

7. Classification based on shape & branching
pattern of duct
 Based on shape of secretory units (tubular or alveolar)
& branching pattern of ducts.
 2 types:
Simple Compound

8. Classification based on shape &
branching pattern of duct
Simple glands
• Simple tubular
• Simple coiled tubular
• Simple branched tubular
• Simple branched alveolar
Compound glands
 Compound tubular
 Compound alveolar
 Compound tubulo-
alveolar

9. Simple glands



10. Compound glands

11. Crypt of Lieberkuhn Sweat glands Fundic glands of stomach Meibomian glands
Brunner glands Submandibular gland Mammary gland

12. Classification based on mode of secretion
• Merocrine: secretion is released by
exocytosis of secretory granules
(pancreas, parotid gland, protein
component of milk from mammary
gland).
• Apocrine: apical portion of cell along
with secretory product is pinched off
(lipid component of milk from the
mammary gland).
• Holocrine: entire cell is shed along
with secretory product (sebaceous
glands).

13. Modes of secretion
Merocrine: secretion by
exocytosis

14. Modes of secretion
• Merocrine: secretion by
exocytosis
• Apocrine: secretion by loss
of cytoplasm
• Holocrine: secretion
through loss of entire cell

15. Classification based on the nature of
secretion
• Serous glands
• Mucous glands
• Mixed glands

16. Serous Glands
 Secretion: Thin, watery,
rich in enzymes, protein in
nature.
 Cytoplasm: granular (stain
darkly from pink to dark
purple with H/E stain) &
rich in RER.
 Nuclei: rounded & basally
placed.

17. Mucous glands
 Secretion: contains
mucopolysaccharides
which collects in the apical
part of cell.
 Cytoplasm: stain very
lightly with H/E stain &
therefore gives empty look.
 Nuclei: basally placed &
flattened (mucoid pushes
the nuclei).

18. Mixed glands
 Contain both serous &
mucous secretory units.
 Sometimes serous cells
form crescentic caps on
mucous acini called as
serous demilunes.

21. Major glands
 Lie completely outside
the alimentary tract &
connected to it by an
excretory duct.
 Compound alveolar or
tubuloalveolar in type.
 Parotid, submandibular,
sublingual.

22. Minor glands
 Small salivary glands situated in the mucous
membrane of:
Lip (labial)
Cheeks (buccal)
Soft palate (palatine)
Tongue (lingual)

23. Functions of Salivary glands
 Secrete saliva composed of water, mucus, proteins,
salts, salivary amylase (ptyalin), immunoglobulins
(IgA) & lactoperoxidase.
 Serves to moisten food.
 Lubricates & moistens oral mucosa and lip.
 Initiates the digestion of carbohydrates.

24. Basic organization

25. Different types of acini
Mucous Serous Mixed

26. Features of serous & mucous cells
EM
LM
Serous cell Mucous cell

27. Differences between serous & mucous acini

28. Differences between serous & mucous cells

29. Parotid gland

30. Submandibular gland

31. Sublingual gland

34. References
1. diFiore’s Atlas of Histology with functional
Correlations, 12th Edition.
2. Textbook of Human Histology. Inderbir Singh, 1st
Edition.
3. Textbook of Histology. GP Pal, 3rd Edition.

35. MCQ
1. All are major salivary glands except:
a) Palatine
b) Parotid
c) Submandibular
d) Sublingual

36. MCQ
2. Holocrine type of secretion is a feature of:
a) Mammary gland
b) Parotid gland
c) Sebaceous gland
d) Pancreas

37. MCQ
3. Sweat gland is an example of:
a) Simple tubular gland
b) Simple coiled tubular gland
c) Simple branched tubular gland
d) Simple alveolar gland

38. MCQ
4. All are true about serous acini except:
a) Smaller in size
b) Stain dark
c) May present as demilune
d) Wide lumen

39. MCQ
5. Expelling of secretion through contraction
is a feature of:
a) Serous cell
b) Mucous cell
c) Serous demilune
d) Myoepithelial cell

40. Body Cavities & Membranes

53. Thank You