1. Lect. 4 - GLANDULAR EPITHELIA

2. What is a GLAND?
• Epithelium that is primarily involved in
secretion.
• An organized collection of secretory
epithelial cells.
• Cells or aggregations of cells whose
function is secretion.

3. • Secretion – Exocytotic
release of products,
not metabolic wastes
• Molecules to be
secreted may be
stored in membrane
bound secretory
granules (vesicles)

5. Glands are merely invaginations of epithelial surfaces, which
are formed during embryonic development by proliferation of
epithelium into the underlying tissues.

6. Gland formation
• Exocrine glands – retain their connection
with the surface epithelium (form ducts)
Ex: Salivary glands
Sudoriferous (sweat) glands
• Endocrine glands – lost their connection to
surface epithelium during development
(form cords and follicles)
Ex: Thyroid gland

7. Cellular Composition
Unicellular glands consist of isolated glandular cells.
Ex. Goblet cells :
• in the lining of the small intestine
• in the lining of the respiratory tract
Goblet cells secrete the glycoprotein mucin, which by the
uptake of water is converted into a slimy substance, mucus.

8. Multicellular glands are composed of clusters
of secretory cells.
• secretory portion embedded in the CT.

9. Nature of secretion
• Serous – watery, high affinity to stain
(water-soluble)
: Sweat glands, Pancreatic glands, Parotid glands
• Mucous – viscous, poor affinity to stains
: Sebaceous glands, sublingual salivary glands,
• Mixed – watery and mucous secretions
: submandibular salivary gland

10. Exocrine VS Endocrine
Exocrine Gland
• release the secretory
product via a system of
ducts that opens upon
one of the surfaces of the
body which are in contact
with the external
environment.
• Have two parts:
– Secretory portion
– Duct
Endocrine Gland
• glands exuding secretions
directly into body fluids,
ultimately blood.
• secretory product (typically
hormones) are released
into the spaces between
the secretory cells
(extracellular space) from
which it enters the
bloodstream.

11. Types of Glands

12. Paracrine glands
In some epithelia, individual cells secrete a
substance that does not reach the
bloodstream but rather affects other cells
within the same epithelium.

13. Exocrine glands / duct glands
• Secretory portion - contains the cells
responsible for the secretory process.
• Ducts - transport the secretions

14. Exocrine glands according to duct system:
• Simple glands have only one unbranched duct.

15. • Compound glands have ducts that branch
repeatedly.

16. Exocrine glands according to cellular
organization of the secretory portion:
Simple glands can have their
secretory portion in the
form of:
• Tubule - a coiled tubule, a
branched tubule,
• Acinus - in which the
cells organize as
spherical or globular
units; any rounded
secretory units.

17. Large intestinal gland – secretory cells line the entire duct.

18. Coiled tube section
• A single coiled tube may appear that it has many sections. Or
a hollow ball organ or hollow tube that yield a tissue
preparation like the given examples above.

19. Sweat glands – each consists of a single tube that is tightly

20. Mucus secreting gland of pylorus– each gland consists of
several tubular secretory portion which converge into one duct.

21. Mucus-secreting gland of penile urethra
Occur in the form
of pockets in
epithelial surfaces.

22. Sebaceous gland- with several secretory acini.

23. Compound glands can be tubular, acinar, or
tubuloacinar

24. Brunner’s gland of the duodenum – duct system is
branched; secretory portion is tubular, branched and coiled.

25. Pancreas (exocrine) – each consists of numerous acini
which drain into a minute duct (D) and drains into branched excretory

26. Submandibular salivary gland – has 2 types of secretory
cells: mucus-secreting cells (A – acinar) and serous cells (T – tubular)
with acinar end-pieces (D-demilunes).

27. Secretion from exocrine glands may occur in
one of three ways:
• Merocrine glands
(eg, the pancreas), the
secretory granules
leave the cell by
exocytosis with no loss
of other cellular
material.
- proteins are usually the
major secretory product.

28. • Holocrine glands
the product of
secretion is shed with
the whole cell—a
process that involves
destruction of the
secretion-filled cells.
- sebaceous glands

29. • Apocrine gland-
(Gr. apo, away from, +
krinein) intermediate
type;—the secretory
product is discharged
together with parts of
the apical cytoplasm
. lipid secretory products in the
breasts and some sweat glands.

30. References:
• Young B. 2009. WHEATER’S FUNCTIONAL
HISTOLOGY. 5TH
Edition. UK: Churchill
Livingstone. Distributor: Phils: C & E Publishing,
Inc.
• Gonzales E. 2009. ESTEBAN and GONZALES’
TEXTBOOK OF HISTOLOGY. 4TH
Edition. PHILS:
C & E Publishing, Inc.