1. Histology 1.4. : Glands
Gland: a single epithelial cell, or grouping of cells specialized
for secretion.
Secretion: energy-consuming process by which the cell takes up
small molecules and transforms them via intracellular
biosynthesis into a more complex product then actively
releases it from the cell. The product is utilized by the
organism in several ways.
Excretion: the organism gets rid of harmful or toxic metabolic
end-products or useless waste material.

2. Classification of glands:
I. Based on morphology: unicellular and multicellular
Unicellular, intraepithelial gland: goblet cell
Intestinal epithelium:
simple columnar epithelium (2)
goblet cells (1)
the arrow shows the nucleus (3)
TEM image of the same
type of unicellular gland,
the goblet cell

3. CLASSIFICATION OF MULTICELLULAR GLANDS:
With ducts: exocrine glands Without ducts: endocrine glands

4. CLASSIFICATION OF EXOCRINE GLANDS (based on morphology):
Simple tubular
Coiled tubular
Branched tubular
Simple acinar
Branched acinar
Compound
tubular
acinar
tubuloacinar

5. SOME EXAMPLES:
Simple tubular gland: intestinal gland of Lieberkühn
Schematic drawing LM microphoto

6. Coiled tubular gland: sweat glands of the skin
Schematic drawing LM microphoto

7. Branched tubular gland: fundic glands in the stomach
Schematic drawing LM microphoto

8. Fundic gland from the stomach - endpiece

9. Simple acinar gland:
Frog skin: mucous
and toxin-producing glands
Compact form without lumen:
sebaceous gland of
mammalian skin

10. Branched acinar gland: larger sebaceous glands of the skin

11. Compound tubular gland: esophageal gland
duct segment
capillary
secretory acini
capillary
lumen

12. Compound tubuloacinar glands:
Mandibular gland Parotid gland

13. Composition of compound glands:
Parenchyma composed of lobes and lobules, ducts
The duct system of the compound glands:
Acinus
Intercalated duct
Striated (salivary duct)
Interlobular duct
Lobar duct
Main duct

14. Model of the gland: a bunch of grapes: berry= acinus
stalk of berry: intercalated duct

15. Intralobular striated (salivary) duct
Interlobular duct

16. II. Type of secretory product:
Serous gland: composed of acini with narrow lumen (1)
secretory cells have round, basally located nuclei (2)
the cytoplasm of the cells is basophilic (3)
Pancreas
(see the micrograph)
and parotid gland
are purely serous
producing thin
watery fluid
rich in proteins
(mainly enzymes) 3 1 2

17. 2. Mucous glands: composed of acini with wide lumen
secretory cells have flattened nuclei at the base
their cytoplasm is very weakly stained
Esophageal glands
(see the micrograph)
are purely mucous
producing thick
viscous fluid, rich in
mucopoly-
saccharides
for lubrication and
protection of internal
body surfaces

18. 3. Seromucous glands: mucous acini surrounded by serous cells
forming a demilune shape
The submandibular gland of some species (monkey, human, cattle) is
seromucous. Red arrows point at mucous cells, blue arrows point at
the demilune –shaped group of serous cells (Demilune of Gianuzzi)

19. Seromucous gland, haematein-eosin
staining
Seromucous gland, alciane blue
staining

20. III. Modes of secretion:
Merocrine secretion:
The secretory process is an exocytosis
The secretory cell remains completely intact
Most of the glands secrete in a merocrine manner
Exocrine pancreas Submandibular gland

21. the secretum is gathered at the apical portion of the cell
2. Apocrine secretion:
the secretum is gathered at the apical portion of the cell
the secretum leaves the cell membrane-bounded (pinched off)
the cell remains alive, but a part of it goes with the secretory droplet
Examples: sweat and mammary glands

22. Membrane-bound secretory droplets of a sweat gland

23. 3. Holocrine secretion:
the secretory cell gradually fills up with secretum
the cell organelles degenerate
the cell dies, its membrane breaks and the secretum empties
The sebaceous gland is a holocrine gland. Dead cells are replaced
by the mitotic divison of basal cells

24. Absorptive epithelium:
its main function is to absorb. Morphology of these epithelial cells exhibit
cuticular border (intestine) or brush border (kidney tubules).
Please note: at fine structural level both are microvilli !
EM micrograph of the apical
surface with microvilli
Intestinal epithelium: the arrow shows
the cuticular border

25. Pigmented epithelium:
Epithelial cells contain melamosomes: brown color EM
Pigmented epithelium in the eye
at LM level shows brown pigmentation.
At EM level the melanosomes appear as
electron dense bodies in the cytoplasm. LM

26. Sensory epithelia: Main function is sensation
Types: primary, secondary sensory epithelium
true nerve cells
Primary sensory epithelium: olfactory epithelium

27. Secondary type of sensory epithelia:
Example: sensory cells of the taste buds