1. A Few Additional Slides to Help Your Study for BIOL 232 Lecture Exam #1
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2. Figure 4.5 Types of multicellular exocrine glands.
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
One thing that is very interesting as we see cells organize into more complex structures like tissues is that you can have the formation of ducts (we see these a lot in glands). In the above slide, please note how there are three different cell aspects (epithelia)… light yellow is surface epithelia, dark yellow shows the ducts, and red shows secretory epithelia.
What I want you to notice is how the duct branching and the types of secretory structures can be mixed and matched to form a variety of different ducts. The two secretory types are tubular and alveolar. The types of ducts are simple, branched, and compound branched. Be sure to look at the above different types of ducts. Notice that the most complex type is the compound tubuloalveolar ducts that are seen in our salivary glands.
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

3. Figure 4.6 Chief modes of secretion in human exocrine glands.
Secretory
cell fragments
Secretory
vesicles
(a) Merocrine glands
secrete their products
by exocytosis.
Glands can also produce their secretions in two different ways. These are seen in the above. Merocrine glands release their secretions using secretory vesicles that exocytotically release their contents. Holocrine glands, by contrast, release cell fragments filled with the secretory material. Our sweat glands would be an example of a merocrine gland. An example of a holocrine gland is seen in some of our sebaceous glands.
(b) In holocrine glands, the
entire secretory cell
ruptures, releasing
secretions and dead
cell fragments.