If glands are categorized by shape, alveolar glands contrast with tubular glands. Alveolar glands have a saclike secretory portion, and are also termed saccular glands. They typically have an enlarged lumen (cavity), hence the name similar to alveoli, the very small air sacs in the lungs.
Section of pancreas of dog. X 250.
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Some sources draw a clear distinction between acinar and alveolar glands, based upon the size of the lumen. A further complication in the case of the alveolar glands may occur in the form of still smaller saccular diverticuli growing out from the main sacculi.
Branched alveolar glands are classified as follows:
|simple branched acinar
or compound tubulo-acinar
or compound tubuloalveolar
|glands that start out as simple branched tubular, and branch further to terminate in alveoli||salivary glands,|