78
UNIT 2
Basic Tissues
Type
Connective Tissue
Cells
Connective
Tissue Fibers
Organization of
Fibers and Cells
Main Locations
Main Functions
Connective Tissue Proper
Dense irregular
connective tissue
Predominantly
f broblasts; other
connective tissue
cells occasionally
present
Collagen f bers,
elastic f bers,
reticular f bers
Fewer cells and
more f bers; f
bers
arranged randomly
without a def nite
orientation in
relatively less ground
substance
Dermis o± the skin,
capsules o± many
organs
Resists stress
±rom all
directions;
protects organs
Dense regular
connective tissue
Predominantly
f broblasts; other
connective tissue
cells occasionally
present
Collagen f bers,
elastic f bers,
reticular f bers
Fewer cells and
more f bers; f
bers
arranged in uni±orm
parallel bundles
Tendons, ligaments
Provides
resistance to
traction ±orces
Loose
connective tissue
Fibroblasts,
macrophages,
adipocytes, mast
cells, plasma cells,
leukocytes
Collagen f bers
predominate;
elastic and
reticular f bers
also present
More cells and
±ewer f bers; f
bers
randomly
distributed
in abundant ground
substance
Lamina propria
o± gastrointestinal
tract; around the
nerves and vessels
(in adventitia layer)
Provides
protection,
suspension, and
support; conduit
±or vessels and
nerves; environ-
ment ±or immune
de±ense ±unction
Specialized Connective Tissues
Adipose
connective tissue
Predominantly
adipocytes (±at cells);
f broblasts and other
connective tissue
cells
occasionally
present
Collagen f bers
and reticular
f bers
Fibers ±orm f ne
meshwork that
separates adjacent
adipocytes
Hypodermis o± the
skin, mammary
glands, and around
many organs
Provides
energy
storage,
insulation;
cushioning o±
organs; hormone
secretion
Reticular
connective tissue
Fibroblasts,
reticular cells,
hepatocytes,
smooth muscle
cells, Schwann cells
depending on the
location
Reticular f bers
Fibers ±orm delicate
meshlike network;
cells with process
attached to the f bers
Liver, pancreas,
lymph nodes,
spleen, and bone
marrow
Provides support-
ive ±ramework
±or hematopoietic
and parenchymal
organs
Elastic
connective tissue
Predominantly
f broblasts or
smooth muscle cells;
other connective
tissue cells occasion-
ally present
Elastic f bers
predominate;
collagen and
reticular f bers
also present
Fibers arranged
in parallel wavy
bundles
Vertebral ligaments,
walls o± the large
arteries
Provides fl exible
support ±or the
tissue; reduces
pressure on the
walls o± the
arteries
Embryonic Connective Tissues
Mesenchymal
connective tissue
Mesenchymal cells
Reticular f bers
and collagen
f bers
Scattered f bers
with spindle-
shaped cells having
long
cytoplasmic
processes;
mesenchymal cells
uni±ormly distributed
Embryonic
mesoderm
Gives rise to all
connective tissue
types
Mucous
connective tissue
Spindle-shaped
f broblasts
Collagen f bers
predominate; ±ew
elastic and reticu-
lar f bers
Fibers and
f broblasts randomly
displayed in jellylike
matrix (Wharton
jelly)
Umbilical cord,
subdermal layer
o± the ±etus, dental
pulp o± the devel-
oping teeth, nucleus
pulposus o± the disk
Provides cushion
to protect the
blood vessels in
the umbilical cord
TABLE 4-3
Connective Tissue Types
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