Page 70 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

52 Veterinary Histology of Domestic Mammals and Birds

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2.28 Large intestine (dog). In cross-section, the cells of exocrine tubular glands form a ring around a central
lumen into which the secretory product is deposited. Goblet cells within the epithelium stain lightly with
haematoxylin and eosin. Haematoxylin and eosin stain (x100).

2.29 Columnar epithelial cell in the small intestine of 2.30 Goblet cell (schematic).
a dog (schematic).

With the use of mucin special stains (PAS, mucicarmine), glands consisting of a (usually) single secretory unit and a
these granules selectively stain bright red–magenta. The single unbranched or minimally branched duct are termed
secretory product is released by exocytosis. simple glands (e.g. sweat glands).
Multicellular intra-epithelial exocrine glands are Those in which multiple secretory units are connected
found in the pseudostratified epithelium of the airways of to the surface by a highly branched system of ducts are
birds. referred to as compound glands.
The following criteria for categorising types of glands
EXTRA-EPITHELIAL GLANDS (GLANDULAE are discussed in more detail below:
EXOEPITHELIALES)
Extra-epithelial glands are located in the connec- • shape of the secretory unit,
tive tissue underlying the epithelium. They are always • structure of the duct system,
multicellular. Their secretions are produced in secre- • mode of secretion and
tory units (secretory end pieces) and are conveyed • chemical composition of the secretory product.
to the surface of the epithelium by ducts. Exocrine

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