The secretory product of an acinus is drained sequentially by the following :

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• The secretory product of an acinus is drained
  sequentially by the following
• An intercalated duct (lined by low
  squamous-to-cuboidal epithelium). The
  intercalated duct is longest in the parotid
  gland.
• A striated duct (a segment lined by
  cuboidal-to-columnar epithelial cells with basal
  infoldings containing numerous mitochondria). The
  striated duct is well developed in the
  submandibular gland. The epithelium of the
  striated duct participates in ion and water
  transport and secretes kallikrein. Both
  intercalated and striated ducts are modestly
  developed in the sublingual gland.
• The intercalated, striated, and excretory
  intralobular segments are observed within the
  lobule, embedded in the connective tissue septa.
  An excretory intra-lobular duct is initially
  lined by cuboidal-to-columnar epithelium it
  becomes pseudostratified columnar when it joins
  the interlobular duct.

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Intralobular ducts join to form the interlobular
duct, which is located outside the lobule,
between adjacent lobules. An interlobular duct is
lined by pseudostratified columnar epithelium.
Interlobular ducts converge to form a lobar
duct. Lobar ducts (lined by stratified columnar
epithelium, one of the few sites in the body
lined by this type of epithelium) join the main
duct (lined by stratified squamous epithelium)
near the opening into the oral cavity.
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• Bile has five major functions
• The excretion of cholesterol, phospholipids, bile
  salts, conjugated bilirubin, and electrolytes.
• Contributes to fat absorption in the intestinal
  lumen.
• Transports IgA to the intestinal mucosa by the
  enterohepatic circulation.
• The excretion of metabolic products of drugs and
  heavy metals processed in the hepatocyte.
• Conjugated bile acids inhibit the growth of
  bacteria in the small intestine.

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• The transport of bile and other organic
  substances from the hepatocyte to the lumen of
  the bile canaliculus is an adenosine triphosphate
  (ATP)-mediated process. Four ATP-dependent
  transporters, present in the canalicular plasma
  membrane, participate in transport mechanisms of
  the bile.
• Multidrug resistance 1 transporter (MDR1), which
  mobilizes cholesterol across the plasma membrane.
  
• Multidrug resistance 2 transporter (MDR2), which
  transports phospho-lipids.
• Multispecific organ anionic transporter (MOAT),
  which exports bilirubin glucuronide and
  glutathione conjugates.
• Biliary acid transporter (BAT), which transports
  bile salts.

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