CHAPTER 16
Digestive Glands and Associated Organs
313
Figure 16-7A.
Striated duct, submandibular gland.
H&E,
3
845
Striated ducts
are lined by
simple cuboidal
or
columnar cells
with
centrally positioned nuclei
. Their cytoplasm shows
striations
in
the basolateral region, hence the name. The striations are due to deep indentations in the plasma membrane (
basolateral folds
),
which increase the surface area occupied by pumps involved in
ion
and
fl uid transport
. The folds contain many
mitochondria
that
provide adenosine triphosphate for active transport. The
striated ducts
collect
primary saliva
(produced by acinar cells) from the
intercalated ducts
. The main function of the striated ducts is modulation of the
pH
and
ion composition
of the saliva. The striated
ducts remove
Na
+
and
Cl
ions
in the primary saliva from the lumen and transport these ions to the interstitial tissues. Striated ducts
also pump
K
+
and
HCO
3
into the saliva fl uid. This results in a
hypotonic alkaline saliva
(secondary saliva), which moves from the
striated ducts to the interlobular ducts, then to the main duct, and eventually enters the oral cavity. Saliva plays important roles in
moistening and cleansing the oral cavity, helping to repair oral tissues, infl
uencing the pH (
buffering
) in the oral cavity, stimulating
the taste buds, helping to digest food, helping in the mineralization and hardening of the enamel of posterupted teeth, and destroying
bacteria by antimicrobial action.
D. Cui
Striations
Striations
Striations
Interstitial
Interstitial
tissue
tissue
Interstitial
tissue
Serous
Serous
acinus
acinus
Serous
acinus
Lumen
Lumen
Lumen
Na
+
Cl
_
Na
+
K
+
Cl
_
HCO
3
_
Na
+
Cl
_
Interstitial
tissue
Striated
duct
A
Basal
membrane
enfolding
Mitochondrion
Nucleus
Basement
membrane
Lumen
B
Figure 16-7B.
Intralobular duct, sub-
mandibular gland.
EM,
3
3,382; inset
3
6,779
The duct shown here appears to be at the
transition between a
striated intralobular
duct
and an
interlobular duct
. Some of
the lining cells, such as the one shown in
the
inset
, have features of a striated duct
in that there are extensive
basolateral
folds
containing numerous mitochondria.
These are the same features that account
for the eosinophilic striations seen in these
cells in H&E-stained sections for light
microscopy.
previous page 328 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online next page 330 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online Home Toggle text on/off