74
UNIT 2
Basic Tissues
CLINICAL CORRELATION
Figure 4-18C.
Obesity.
Hypertrophic obesity
is a disorder characterized by an
increase in total body fat, particularly by expansion
(
hypertrophy
) of preexisting fat cells. Obesity increases
the risk for a number of conditions, including diabetes,
hypertension, high cholesterol, stroke, and coronary
artery disease. Obesity may also increase the risk for
some types of cancer, and it is a risk factor for the devel-
opment of osteoarthritis, pancreatitis, and sleep apnea.
Obesity can result from a sedentary lifestyle and the
chronic ingestion of excess calories; genetic predisposi-
tion may also play a role in the development of obesity.
The possible treatments include exercise, diet, medica-
tions, and surgery. By contrast,
hyperplastic obesity
is
excessive weight gain associated with childhood-onset
obesity, characterized by the creation of new fat cells.
Types of Connective Tissue: Specialized Connective Tissues
Figure 4-18A.
Adipose tissue, mammary gland.
H&E,
3
68; inset
3
178
Adipose tissue
is a special form of connective tissue and
has a rich neurovascular supply.
Adipocytes
appear
white here, and this tissue is referred to as
white adi-
pose tissue
. Each adipocyte contains a single, large lipid
droplet in its cytoplasm, so the cells are called
unilocular
adipose cells
. Most of the cytoplasm is occupied by the
lipid droplet, and the nucleus is displaced to one side.
Each adipocyte is surrounded by a basal lamina. This
type of adipose tissue is found throughout the adult
human body. There is another type of adipose tissue
that is highly specialized, called
brown adipose tissue
.
It is composed of
multilocular adipocytes
; each adipo-
cyte contains multiple lipid droplets in its cytoplasm.
This tissue is mainly found in hibernating mammals
and newborn infants but can also be found scattered
in some areas in adults, such as the esophagus, trachea,
posterior neck, and interscapular areas as vestigial rem-
nant tissue. Tumors sometimes arise from the remnant
brown adipose tissue and are called
hibernomas
.
Figure 4-18B.
A representation of adipose tissue.
Adipocytes
(
fat
cells
) are scattered within a loose
collagenous supporting tissue in this unilocular adi-
pose tissue. Each adipose cell contains a single large
drop of lipid; it has a thin rim of cytoplasm around the
lipid, and its fl
attened nucleus is located in the periph-
ery of the cell.
Adipocytes
are the primary site for
stor-
age of energy
, and lipid deposition and mobilization
are regulated by
hormonal factors
(steroids, insulin,
thyroid hormone, etc.). Adipocytes also play a role in
the synthesis of some hormones such as
leptin
. Dur-
ing childhood, the adipocyte numbers may increase
depending on nutrition and other factors, but in adult-
hood, adipocyte numbers normally remain constant.
Adipose
cells
Nuclei of
adipocytes
Dense irregular
connective tissue
Adipose tissue
Adipose cells
A
D. Cui
B
Collagen fiber
Reticular fibers
Blood vessel
Fibroblast
Adipocyte
D. Cui
C
Collagen bundles
pushed to the side
Expanded adipocytes
containing huge
lipid droplets
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