Connective TissueConnective Tissue

Different types of connective tissues maintain form of the body by providing the matrix which connects and bind cells and organs of the body.

Connective tissue consists of:CellsFibersGround substance

Wide variety of connective tissue types reflects variation in the composition and the amount of the three components

Cells Cells of the of the

Connective TissueConnective Tissue

Fibroblast Most dominant cell type of connective tissue Synthesis of extracellular matrix components Synthesis of fiber proteins Production of growth factors Fibroblast features Fibrocyte features

MacrophageMacrophage

Ultrastructural featuresUltrastructural features Derived from monocyteDerived from monocyte They form the Mononuclear They form the Mononuclear

Phagocyte SystemPhagocyte System Kupffer cell, Microglia, Osteoclast,Kupffer cell, Microglia, Osteoclast,

Langerhans cell, dendritic cell, Langerhans cell, dendritic cell, Multinuclear giant cell, Epitheloid Multinuclear giant cell, Epitheloid

cellcell FunctionsFunctions

Mast CellMast Cell

Ultrastructural featuresUltrastructural features Secretory granules and contentSecretory granules and content MetachromasiaMetachromasia FunctionFunction TypesTypes

Connective tissue mast cellConnective tissue mast cellMucosal mast cellMucosal mast cell

Plasma CellPlasma Cell

Ultrastructural featuresUltrastructural features OriginOrigin FunctionFunction

Adipocytes and Leukocytes

Will be described later. Adipocytes is a connective tissue cell

specialized in fat storage and heat production Leukocytes leave the blood stream by

Diapedesis. They release chemical mediators of inflammation.

Fibers Fibers of theof the

Connective TissueConnective Tissue

Collagen Fibers Made of collagen protein which constitutes

30% of human body They form a family of >25 produced by

different types of cells Classifications:

Collagen forming long fibrils I, II, III, V, XIFibril-associated collagen IX, XII, XIVCollagen forming anchoring fibrils VIICollagen forming network IV

Made mainly of glycine and proline

Reticular FibersReticular Fibers Made of collagen type III They are very thin and form an extensive net

work in certain organs They contain 6-12% hexose sugars They are found in parenchymatous

organs e.g. liver and spleen Argyrophilia, PAS +

Elastic FibersElastic Fibers A system consists of Oxytalan, Elaunin, and

Elastic fibers. Oxytalan fibers are not elastic but resistant to

pulling e.g. zonular ligament and dermis. Consists of fibromodulin and fibrillin

Elaunin fibers: elastin start to deposit between oxytalan fibers e.g. around sweat glands and dermis

Elastic fibers: rich in elastin surrounded by a sheath of microfibrils of oxytalan

Made of, in addition to glycine and prolin, desmosine and isodesmosine

Ground Substance

Consists of hydrated , colorless, transparent mixture of macromolecules.

It acts as a lubricant and a barrier Composed of:

GlycoseaminoglycansProteoglycansGlycoproteins

Glycoseaminoglycans

Composed of linear polysaccharides formed of repeating disaccharides units made of uronic acid and hexosamine

They are intensely hydrophilic and basophilic and acts as polyanion due to OH ,COO, and SH groups

Types and distribution

Hyaluronic Acid Chondroitin sulfate Dermatin sulfate keratin sulfate

Proteoglycans Consists of a core protein to which different types

of glycosaminoglycan are attached except hyaluronic acid

Some are free in the ground substance e.g. Aggrecan and others are attached to cell membrane e.g. Syndecan Fibroglycan

GlycoproteinsGlycoproteins

Made dominantly of protein to which attached abranched carbohydrates

Plays a role in the interaction between adult and embryonic cells and adhesion of cells into their sustrate

Examples Fibronectin Laminin

Types of Connective TissueTypes of Connective Tissue Connective tissue properConnective tissue proper

Loose connective tissueLoose connective tissueDense connective tissueDense connective tissue

RegularRegularIrregularIrregular

Connective Tissue with Special Connective Tissue with Special PropertiesProperties

Adipose Tissue Elastic Tissue Hematopoietic Tissue Mucus Tissue Reticular tissue

Adipose Tissue A special type of connective tissue in which

adipocytes predominate It serves as energy depot It shapes the body Act as a shock absorber Thermal insulation Keeps some organs

in place e.g. Kidney

Unilocular (Yellow) adipose Tissue It is white to yellow because of carotenoids Most common in adult Almost found everywhere in the body Distribution is affected by age and sex Adipose tissue is divided into incomplete

lobules by connective tissue It is richly vascularized Leptin is produced by fat cell to regulate

amount of adipose tissue in the body Ultrastructure of the adipose cell

Multilocular (Brown) Adipose Tissue It is brown because of richness of capillaries

and numerous mitochondria containing colored cytochromes

It has a localized distribution Ultrastructure of adipose cell Cells are directly innervated

by sympathetic nerves

Clinical Applications Immediate hypersensitivity reaction and

Anaphylactic shock Progressive systemic sclerosis and keloid Marfan syndrome and fibrillin gene mutation Ehlers-Danlos IV, VI, VII, Scurvy, Osteogenesis

imperfecta