1. Glands
Chapter 4, Section 2

2. Glandular Epithelia
A gland is one or more cells that makes and secretes an aqueous fluid
Classified by:
Site of product release—endocrine or exocrine
Relative number of cells forming the gland— unicellular (e.g., goblet cells) or multicellular

3. Endocrine Glands Ductless glands
Secrete hormones that travel through lymph or blood to target organs

4. Exocrine Glands More numerous than endocrine glands
Secrete products into ducts
Secretions released onto body surfaces (skin) or into body cavities
Examples include mucous, sweat, oil, and salivary glands

5. Unicellular Exocrine Glands
The only important unicellular gland is the goblet cell
Goblet cells secrete mucin, which dissolves in water to become mucus

6. Microvilli Secretory vesicles containing mucin Rough ER Golgi
apparatus
Nucleus
(a)
(b)
Figure 4.4

7. Multicellular Exocrine Glands
Multicellular exocrine glands are composed of a duct and a secretory unit
Classified according to:
Duct type (simple or compound)
Structure of their secretory units (tubular, alveolar, or tubuloalveolar)

8. Compound duct structure
Simple duct structure
(duct does not branch)
Compound duct structure
(duct branches)
Tubular
secretory
structure
Simple tubular
Simple branched
tubular
Compound tubular
Example
Intestinal glands
Example
Stomach (gastric)
glands
Example
Duodenal glands of small intestine
Alveolar
secretory
structure
Simple
alveolar
Simple branched
alveolar
Compound alveolar
Compound
tubuloalveolar
Example
No important
example in humans
Example
Sebaceous (oil)
glands
Example
Mammary glands
Example
Salivary glands
Surface epithelium
Duct
Secretory epithelium
Figure 4.5

9. Modes of Secretion Merocrine Holocrine
Products are secreted by exocytosis (e.g., pancreas, sweat and salivary glands)
Holocrine
Products are secreted by rupture of gland cells (e.g., sebaceous glands)

10. Compound duct structure
Simple duct structure
(duct does not branch)
Compound duct structure
(duct branches)
Tubular
secretory
structure
Simple tubular
Simple branched
tubular
Compound tubular
Example
Intestinal glands
Example
Stomach (gastric)
glands
Example
Duodenal glands of small intestine
Alveolar
secretory
structure
Simple
alveolar
Simple branched
alveolar
Compound alveolar
Compound
tubuloalveolar
Example
No important
example in humans
Example
Sebaceous (oil)
glands
Example
Mammary glands
Example
Salivary glands
Surface epithelium
Duct
Secretory epithelium
Figure 4.5