316
UNIT 3
Organ Systems
Figure 16-10A.
Pancreatic acinar cells.
EM,
3
9,509; inset (
color
), H&E,
3
157
Pancreatic acinar cells
are protein-synthesizing cells and contain many
secretory
(
zymogen
)
granules
in the apical region of the
cytoplasm and plentiful
RER
in the basal cytoplasm of the cells. A
Golgi complex
is seen close to the nucleus of the cell. A
lumen
is
located at the apical region of the acinar cells, where zymogen granules are released. Several
junctional complexes
near the lumen
indicate the fused borders between the neighboring acinar cells. The
inset color microphotograph
shows pancreatic cells arranged
in
acini
as a secretory unit. These cells have basally positioned nuclei.
Zymogen
granules
Golgi
complex
Nucleus of pancreatic
acinar cell
Rough endoplasmic
reticulum (RER)
Pancreatic acinar cells
Islet of
Islet of
Langerhans
Langerhans
Islet of
Langerhans
Junctional
Junctional
complexes
complexes
Junctional
complexes
Lumen
Lumen
Lumen
RER
RER
RER
Nucleolus
A
Lumen
Lumen
Lumen
Centroacinar
cells
Zymogen
granules
Centroacinar
cells
Zymogen
Zymogen
granules
granules
Zymogen
granules
Nucleolus of acinar cell
Nucleolus of acinar cell
Nucleolus of acinar cell
Nucleus
Nucleus
Nucleus
B
Figure 16-10B.
Centroacinar cells,
pancreas.
EM,
3
5,891; inset (
color
),
H&E,
3
628
Centroacinar cells
are not protein-
synthesizing cells and they do not have
the features of active protein synthesis
and secretion. They have many
mito-
chondria
but do not have much RER.
These cells form the initial portions of
the
intercalated ducts
and are located
at the center of each
acinus
, hence
their name. The centroacinar cells,
along with intercalated ducts, play
roles in transporting
primary pancre-
atic secretions
. They also secrete a
large volume of fl uid (rich in
sodium
and
bicarbonate
) into the pancreatic
secretions to help neutralize acidic
food contents entering the duodenum
from the stomach.
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