Exocrine Glands

Epithelial cells that are primarily involved in secretion are organized into glands throughout the body. Beginning as an invagination of epithelium during embryonic development, glands have various levels of complexity depending on the need for the secreted product and the location in the organism. There are two major subdivisions of glands: Exocrine glands, which release their contents onto an epithelial surface either directly or via a duct, and endocrine glands which have no duct system, but release their contents into blood.

 


Nomenclature:


Cell quantity

Unicellular exocrine glands are individual epithelial cells that are specialized to secrete product (Fig. 3) and Multicellualr exocrine glands are complex glands composed of many secretory cells (Figs 1,2,4,5,6).

 

Glandular morphology

Multicellular Exocrine Glands are classified depending on the shape of two regions:

            1. Duct portion

            2. Secretory portion

 

            Duct portion

· Glands that have multiple branched ducts that connect to separate

   secretory portions are considered compound glands. Fig. 1

 

· Glands that have only one duct are considered simple glands. Figs. 2,4,5,6


            Secretory portion

            Morphology

· Glandular epithelium arranged in a Tube-like structure is considered a

tubular gland. Fig. 4,6

 

· Glandular epithelium arranged spherically is considered an acinar or

alveolar gland. Fig. 1,2,5

 

            Complexity

· When multiple secretory portions branch from a single duct, the gland is

considered a branched gland. Fig. 4

 

· When the secretory portion coils, it is considered a coiled gland. These are usually

going to be tubular as well. Fig. 6

 

 Exocrine Glands