CONNECTIVE TISSUECONNECTIVE TISSUE

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.

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.

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.

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.

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.

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.

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.

DENSE REGULAR CONNECTIVE TISSUEDENSE REGULAR CONNECTIVE TISSUE

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.

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.

RETICULAR CONNECTIVE TISSUERETICULAR CONNECTIVE TISSUE

MUCOUS TISSUEMUCOUS TISSUE

CONNECTIVE TISSUE CELLS DERIVED FROM THE CONNECTIVE TISSUE CELLS DERIVED FROM THE MULTIPOTENTIALEMBRYONIC MESENCHYME CELLSMULTIPOTENTIALEMBRYONIC MESENCHYME CELLS

FIBROBLASTFIBROBLAST

PLASMA CELLSPLASMA CELLS

MAST CELLSMAST CELLS

COLLAGEN FIBERSCOLLAGEN FIBERS