As ducts travel from the
acinus which generates the fluid to the target, the ducts become larger and the epithelium becomes thicker. The parts of the system are classified as follows: Some sources consider "lobar" ducts to be the same as "interlobar ducts", while others consider lobar ducts to be larger and more distal from the acinus. For sources that make the distinction, the interlobar ducts are more likely to classified with
simple columnar epithelium (or
pseudostratified epithelium), reserving the stratified columnar for the lobar ducts. File:Gray1025.png|Section of
submaxillary gland of
kitten. Duct semidiagrammatic. X 200. File:Gray1173.png|Section of portion of
mamma.
Intercalated duct The
intercalated duct, also called intercalary duct (ducts of Boll), is the portion of an
exocrine gland leading directly from the
acinus to a
striated duct. The intercalated duct forms part of the
intralobular duct. This duct has the thinnest epithelium of any part of the duct system, and the epithelium is usually classified as "low"
simple cuboidal. They are found in both the
pancreas and in
salivary glands.
Striated duct A
striated duct ('''Pflüger's ducts''') is a
gland duct which connects an
intercalated duct to an interlobular duct. It is characterized by the basal infoldings of its plasma membrane, characteristic of ion-pumping activity by the numerous mitochondria. Along with the intercalated ducts, they function to modify salivary fluid by secreting HCO3− and K+ and reabsorbing Na+ and Cl− using the Na-K pump and the Cl-HCO3 pump, making the saliva hypotonic. Their
epithelium can be
simple cuboidal or
simple columnar. Striated ducts are part of the
intralobular ducts. They are found in the
submandibular gland,
sublingual duct, and the
parotid gland, but are more developed in the parotid gland. They are not present in
pancreas.
Intralobular duct An
intralobular duct is the portion of an
exocrine gland inside a
lobule, leading directly from
acinus to an
interlobular duct (between lobules). It is composed of two subdivisions, the
intercalated duct and the
striated duct. In the human mammary gland, the intralobular duct is a part of the glandular system that resides within the lobules. Lobules contain clusters of ducts whose secretory alveolies are drained by the intralobular duct. The intralobular ducts are usually lined with simple cuboidal epithelial cells that are lined by myoepithelial cells as well. The intralobular ducts of the lobules drain into the interlobular ducts between lobules. They can be seen in: •
pancreas •
salivary glands ==See also==