2. COLLAGEN FIBERS
• Collagen fibers are tough ,thick ,fibrous
proteins that do not branch.
• They are most abundant fibers.
• Collagen is secreted into extracellular
matrix in the form of tropocollagen
which consists of 3 polypeptide chains
bound together to form a helical
structure 260 nm long and 1.5 nm in
diameter. In ext cell matrix these
molecules polymerize to form 5
different type of collagen designated I
to V on the basis of amino acid
composition ,morphology and physical
properties.
• Type I comprises 90%. They are found in
c.t skin, tendon, ligament and bone.
They are strong and offer great
resistance to tensile stresses. Parallel
collagen fibers are further arranged in
strong bundles.
3. CONTINUED….
• Type II collagen fibers are found in hyaline and
elastic cartilage. They consist of very fine fibrils
which are disperse in ground substance. These
fibers are pressure resistant.
• Type III collagen fibers are thin branching
reticular fibers that form the delicate supporting
mesh work in such organs as the lymph nodes,
spleen and bone marrow.
• Type IV collagen fibers present in the basal
lamina.
• Type V is found in small amounts in most
connective tissues.
4. RETICULAR FIBERS • These fibers mainly consist of
type III collagen.
• These are thin fibers and
form a delicate netlike
framework in the liver, lymph
nodes, spleen, hemopoietic
organs and other locations
where blood and lymph are
filtered.
• They support capillaries,
nerves and muscle cells.
• They are visible when tissues
and organs are silver stained.
5. ELASTIC FIBERS • Thin, small branching fibers that allow
stretch.
• Less tensile than collagen fiber and are
composed of micro fibrils and protein
elastin.
• When stretched the elastic fibers return
to their original size without
deformation.
• Found in abundance in the lungs,
bladder and skin.
• Presence in the aorta walls and
pulmonary trunk allows for stretching
and recoiling of these vessels during
powerful blood ejections from the heart
ventricles.
• Smooth muscles synthesize the elastic
fibers in walls of large vessels.
6. GROUND SUBSTANCE
AND CONNECTIVE
TISSUE
• Ground substance in connective
tissue consist of amorphous,
transparent, colorless extracellular
matrix and has a high water
content.
• It supports, surrounds and binds all
of the connective tissue cells and
fibers.
• It consist of chains of
glycosaminoglycans,
proteoglycans, and adhesive
glycoprotein. Hyaluronic acid is the
predominant glycosaminoglycan in
connective tissue.
• Proteoglycans are large molecules
consisting of 90 -95 %
carbohydrates.
7. CONTINUED….
• Adhesive glycoproteins bind cells to the fibers
e.g. fibronectin, integrin and laminin.
– Fibronectin binds connective tissue cells, fibers
and proteoglycans, thereby interconnecting all
three components of the connective tissue.
– Integrin bind to extracellular collagen fibers and to
actin filaments.
– Laminin is a major component of cell basement
membrane. This protein binds epithelial cells to
basal lamina.
8. LOOSE (AREOLAR) CONNECTIVE
TISSUE
• Supports the epithelial
lining of the
gastrointestinal,
respiratory and urinary
tracts, forms the deeper
layers of the skin.
• Loosely arranged and
wavy in appearance in
unstretched
preparations.
• Open spaces between
collagen fibers with
ground substance which
remains unstained during
tissue preparation.
10. CONTINUED….
• Mechanical support is the primary function e.g.
tendons.
• Parallel, closely packed bundles of collagen
separated by a small quantity of intercellular
ground substance.
• Their fibrocytes contain elongated nuclei parallel
to the fibers and sparse cytoplasmic folds.
• Collagen bundles of tendons (primary bundles)
aggregate into larger bundles (secondary
bundles) enveloped by loose connective tissue
containing blood vessels and nerves.
11. DENSE IRREGULAR CONNECTIVE
TISSUE
• Typically found in the skin
where collagen fibers are
arranged in coarse irregular
interwoven bundles which
confer great tensile strength.
• The fibroblasts are inactive
with highly condensed nuclei
and minimal cytoplasm.
