This document discusses the structure and classification of glands in the digestive system, including salivary glands, pancreas, liver, and gallbladder. It describes the histological components and organization of these glands, such as secretory units, duct systems, cell types, and lobule structure. Key terms are defined for classifying different parts of the gland based on position, morphology, and secretory products. Diagrams and images illustrate these structural features at the light microscopy and electron microscopy levels.

1. DIGESTIVEDIGESTIVEDIGESTIVEDIGESTIVEDIGESTIVEDIGESTIVEDIGESTIVEDIGESTIVE
GLANDSGLANDSGLANDSGLANDSGLANDSGLANDSGLANDSGLANDS

3. EXTRINSIC/EXTRA-MURAL GLANDS
OF DIGESTIVE SYSTEM
Salivary Glands
Pancreas
Liver
Gall Bladder

4. GENERAL ORGANIZATION AND
COMPONENTS OF DIGESTIVE SYSTEM
Source: Ham. 1957. Histology. 3rd Edition.
EXTRINSIC GLAND/
EXTRA-MURAL GLAND
INTRINSIC GLAND
INTRINSIC GLAND
TUBULAR PORTION

5. TERMS USED TO DESCRIBE THE
BRANCHED DUCT SYSTEM
OF LARGE EXOCRINE GLANDS
INTERCALATED DUCTS
STRIATED DUCTS
EXCRETORY DUCTS
INTRALOBULAR DUCTS
INTERLOBULAR DUCTS
INTERLOBAR DUCTS
BASED ON POSITION
IN THE GLAND
BASED ON MORPHOLOGY
OF THE EPITHELIUM

6. Classification of ducts by position in the gland
Blue = CT
Red = ducts
Green = gland
tissue
Main Duct
(interlobar)
Duct from a lobe
(interlobar)
Duct from a
lobule
(interlobular)
Duct within a
lobule
(intralobular)

7. TERMS USED TO DESCRIBE THE
BRANCHED DUCT SYSTEM
OF LARGE EXOCRINE GLANDS
INTERCALATED DUCTS
STRIATED DUCTS
EXCRETORY DUCTS
INTRALOBULAR DUCTS
INTERLOBULAR DUCTS
INTERLOBAR DUCTS
BASED ON POSITION
IN THE GLAND
BASED ON MORPHOLOGY
OF THE EPITHELIUM

8. Morphology of structures associated with
secretory units in digestive glands
From Junqueira et al. 1975

9. Function of striated ducts
From Junqueira et al. 1975

10. TERMS USED TO DESCRIBE THE
SECRETORY PRODUCTS
OF LARGE EXOCRINE GLANDS
• SEROUS (usually acini)
• MUCOUS (usually tubular, frequently
short)
• MIXED (usually short mucous tubules with
serous cells mixed in near the ends)

11. SECRETORY EPITHELIAL CELLS of Salivary Gland
As Viewed at TEM Level
Source: Lentz. 1971. Cell Fine Structure.
Secretory
Granules
Secretory
Granules
Forming
Secretory
Granules
SEROUS-SECRETING CELL MUCUS-SECRETING CELL

12. Mucous-secreting cells
Serous-secreting cells
SUBMANDIBULAR SALIVARY GLAND

13. Mixed secretory unit structure

15. Oral cavity and pharynx
ORAL CAVITY
PHARYNX
Parotid
Submaxillary or Submandibular
Sublingual

16. Structures found in major salivary glands

17. PAROTID SALIVARY GLAND
Serous-secreting Acini
Striated
Ducts

18. Parotid gland
Ross et al. Plate 48

19. Ross et al. Plate 47
Submandibular
(submaxillary)
gland

20. Mucous-secreting cells
Serous-secreting cells
Submandibular (submaxillary) gland

21. Sublingual gland

22. SUBLINGUAL SALIVARY GLAND
Mucous-secreting cells
Serous-secreting cells

23. Parotid gland Sublingual glandSubmandibular
(submaxillary) gland
All serous units (don’t be fooled by adipose) Mostly serous units with areas of mixed units Almost all mixed units

25. Secretory unit and duct structure in the pancreas

26. Pancreas

27. PANCREAS
Islet of Langerhans
(endocrine secretion)
Pancreatic acinar cells
(exocrine secretion)
Duct
Duct

28. PancreasParotid gland

29. COMPARISON OF DIGESTIVE GLANDS
Gland Type of units Striated ducts
Parotid all serous present
Submandibular serous + mixed present
Sublingual all mixed absent or few
Pancreas all serous absent

31. Liver structure

32. HEPATOCYTES
Source: Bloom and Fawcett. 1975.
A Textbook of Histology. 10th Edition.
As Observed at TEM LevelAs Observed at LM Level

33. Lobule organization in the liver

34. HEPATIC LOBULE in pig liver

35. Bile Duct
Hepatic
Arteriole
Hepatic
Portal
Venule
PORTAL TRIAD

36. Source: Bloom and Fawcett. 1975. A Textbook of Histology. 10th Edition.
HEPATIC LOBULE
Hepatic cords/
hepatic plates

37. STRUCTURE-FUNCTION RELATIONSHIPS
WITHIN HEPATIC LOBULE
Source: Ham. 1957. Histology. 3rd Edition.

38. 3-D reconstruction of liver lobule organization

39. HEPATOCYTES
(as seen by LM)
Hepatic cord/hepatic plate
Hepatic sinusoids

40. Cells associated with liver sinusoids
(phagocytic)
(store vitamin A, produce collagen
in space of Disse)

41. STRUCTURE-FUNCTION RELATIONSHIPS
WITHIN HEPATIC LOBULE
Source: Ham. 1957. Histology. 3rd Edition.

42. Bile caniculi
are formed by
adjacent
hepatocytes
and eventually
empty into the
bile duct
branches in
the portal
triads

43. E
Bile caniculi
are formed by
adjacent
hepatocytes
and eventually
empty into the
bile duct
branches in
the portal
triads

44. Bile Duct
Hepatic
Arteriole
Hepatic
Portal
Venule
PORTAL TRIAD

45. Bile duct and gall bladder

47. Wall structure of the gall bladder
Mucosa
simple columnar
epithelium with
apical microvilli
and lateral
intercellular
spaces
lamina propria of
loose FECT
mucous glands
may be present,
mostly in the neck
region
Muscularis externa
bundled smooth
muscle without
clear layers
Adventitia or serosa
loose FECT +/-
mesothelium

48. The epithelium of
the gall bladder
sometimes
extends as a
series of tubular
channels or
sinuses into the
muscularis. These
channels may
become infected.

49. Gall bladder epithelial
cells extract water from
bile by actively
transporting sodium
into the intercellular
spaces, which causes
water to follow by
osmosis. Cell
morphology changes
dramatically during this
process due to the
osmotic changes
around the cells.