158
UNIT ONE
Dense Irregular Connective Tissue
Fibers of
dense irregular connective tissue
are thicker,
interwoven, and more randomly organized. This allows the
tissue to sustain tension exerted from many different direc-
tions. Dense irregular connective tissue is in the dermis, the
inner skin layer.
Elastic Connective Tissue
Elastic connective tissue
mainly consists of yellow, elastic
± bers in parallel strands or in branching networks. Between
these ± bers are collagenous ± bers and ± broblasts. This tis-
sue is found in the attachments between bones of the spinal
column (ligamenta fl ava). It is also in the layers within the
walls of certain hollow internal organs, including the larger
arteries; some portions of the heart; and the larger airways,
where it imparts an elastic quality
(f
g. 5.22)
.
PRACTICE
15
Dif
erentiate between loose connective tissue and dense
connective tissue.
16
What are the Functions oF adipose tissue?
17
Distinguish between reticular and elastic connective tissues.
Cartilage
Cartilage
(kar
ti-lij) is a rigid connective tissue. It provides sup-
port, frameworks, and attachments; protects underlying tis-
sues; and forms structural models for many developing bones.
Cartilage extracellular matrix is abundant and is largely
composed of collagenous fibers embedded in a gel-like
ground substance. This ground substance is rich in a protein-
polysaccharide complex (chondromucoprotein) and contains
a large volume of water. Cartilage cells, or
chondrocytes
(kon
dro-sı¯tz), occupy small chambers called
lacunae
and lie
completely within the extracellular matrix.
A cartilaginous structure is enclosed in a covering of con-
nective tissue called
perichondrium.
Although cartilage tissue
on the surface of the heart, and around certain joints.
Adipose tissue cushions joints and some organs, such as
the kidneys. It also insulates beneath the skin, and it stores
energy in fat molecules.
A person is born with a certain number of fat cells.
Excess food calories are likely to be converted to fat and
stored, so the amount of adipose tissue in the body refl ects
diet or an endocrine disorder. During a period of fasting, adi-
pose cells may lose their fat droplets, shrink, and become
more like ±
broblasts again.
InFants and young children have a continuous layer oF adipose tissue
just beneath the skin, which gives their bodies a rounded appearance.
In adults, this subcutaneous Fat thins in some regions and remains
thick in others. ±or example, in males, adipose tissue usually thick-
ens in the upper back, arms, lower back, and buttocks; in Females, it is
more likely to develop in the breasts, buttocks, and thighs.
Reticular Connective Tissue
Reticular connective tissue
is composed of thin, collage-
nous ±
bers in a three-dimensional network. It helps provide
the framework of certain internal organs, such as the liver,
spleen, and lymphatic organs
(f
g. 5.20)
.
Dense Regular Connective Tissue
Dense regular connective tissue
consists of many closely
packed, thick, collagenous ± bers; a ± ne network of elastic
± bers; and a few cells, mostly ± broblasts. Collagenous ± bers
of dense regular connective tissue are very strong, enabling
the tissue to withstand pulling forces
(f g. 5.21)
. It often binds
body parts as parts of
tendons
and
ligaments.
The blood sup-
ply to dense regular connective tissue is poor, slowing tissue
repair. This is why a sprain, which damages tissues surround-
ing a joint, may take considerable time to heal.
Fat droplet
(a)
(b)
Nucleus
Cell
membrane
Cytsol
FIGURE 5.19
Adipose tissue cells contain large Fat droplets that push the nuclei close to the cell membranes (400×).
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