CHAPTER 17
Endocrine System
341
Insulin-producing
Insulin-producing
(beta) cells
(beta) cells
Insulin-producing
(beta) cells
Capillaries
Capillaries
Capillaries
Exocrine
Exocrine
secretory
secretory
cells
cells
Exocrine
secretory
cells
A
Endocrine secretory cell
Rough endoplasmic reticulum
Golgi complex
Secretory granules in alpha cell
Erythrocyte in lumen of
fenestrated capillary
Secretory granules
Secretory granules
in beta cell
in beta cell
Secretory granules
in beta cell
B
Figure 17-15A.
Pancreatic islet cells, islets of Langerhans.
Immunocytochemistry stain,
3
189
This is an example of an
islet of Langerhans
prepared with
a special immunocytochemistry stain for insulin. Cells
with brown color are
insulin-producing cells
and are the
predominant cells in the islets of Langerhans. Insulin-
producing cells, also called
beta cells
, are distributed
throughout the pancreatic islets. The background counter-
stain is hematoxylin, which makes the endocrine pancreatic
cells appear light blue with darker blue–stained nuclei.
Type 1 diabetes mellitus
is the most common type of dia-
betes in childhood and adolescence (65% of total cases). It
is characterized by insulin deF ciency and sudden onset of
severe
hyperglycemia
,
diabetic ketoacidosis
, and death if
patients are left without insulin treatment. Symptoms also
include
polyuria
,
polydipsia
,
lethargy
, and
weight loss
.
The major cause of the disease is autoimmune destruction
of the insulin-secreting beta cells in the islets of Langerhans
by T cells and humoral mediators (tumor necrosis factor,
interleukin-1, nitric oxide). Treatment options depend
largely on patient and physician preferences and include
baseline doses of insulin plus adjustable premeal doses of
short-acting insulin or rapid-acting insulin analogs.
Figure 17-15B.
Pancreatic islet cells, islets of Langerhans.
EM,
3
13,000; inset (
color
) H&E,
3
1,632
Pancreatic islet cells
, like other types of endocrine cells, are closely associated with
fenestrated
or
sinusoidal capillaries
. The granules
of each of the four main types of cells have slightly different characteristic appearances in electron micrographs. ProF
les of two dif-
ferent cells are visible in this view. The cell adjacent to the wall of the capillary appears to be an
alpha (glucagon-secreting) cell
with
small-to-medium granules that have an electron-dense core with a very narrow electron-lucent surround. The proF
le in the
upper
left
appears to belong to a
beta
(
insulin-secreting
)
cell
with larger granules, a less dense core, and a wide lucent area surrounding the
core. The nuclei of the cells are not present in this view, but note that the cytoplasm of the alpha cell exhibits typical features of a
polypeptide synthesizing and secreting cell: Both RER and a large
Golgi complex
are readily apparent.
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