Connective TissueConnective TissueDr. Ashraf HussainDr. Ashraf Hussain

Connective TissueConnective Tissue

These tissues connect and These tissues connect and support other tissues of the support other tissues of the bodybody

Connective TissueConnective Tissue Mechanical supportMechanical support Medium for exchange of nutrients & Medium for exchange of nutrients &

waste productswaste products Energy store and thermal insulationEnergy store and thermal insulation Defensive functionsDefensive functions a) Barrier b) Engulf bacteriaa) Barrier b) Engulf bacteria c) Antibodies c) Antibodies

Connective tissueConnective tissue Connective tissue comprises a diverse Connective tissue comprises a diverse

group of cells embedded in a tissue-group of cells embedded in a tissue-specific extracellular matrixspecific extracellular matrix

Different type of connective tissue are Different type of connective tissue are responsible for a variety of functionsresponsible for a variety of functions

Classification of connective tissue is based Classification of connective tissue is based on the composition and organization of its on the composition and organization of its cellular & extracellular components and on cellular & extracellular components and on its functions its functions

Structure of connective Structure of connective tissuetissue

CellsCellsIntercellular substance or Intercellular substance or

matrixmatrix

MatrixMatrix Amorphous ground substanceAmorphous ground substance Thread like formed elements called Thread like formed elements called

fibers (collagen fibers, reticular fibers (collagen fibers, reticular fibers, elastic fibers)fibers, elastic fibers)

Tissue fluidTissue fluid

Cellular component

interspersed in intercellular substance

different kinds of cells

Fibers – part of the “formed substance” of C.T.

embedded in ground substance

Matrix = ground substance + fibers

Connective tissue cellsConnective tissue cells Resident cell Resident cell

populationpopulation FibroblastsFibroblasts MacrophagesMacrophages Adipose cellsAdipose cells Mast cellsMast cells Undifferentiated Undifferentiated

mesenchymal cellsmesenchymal cells

Wondering cell Wondering cell populationpopulation

Lymphocytes Lymphocytes Plasma cellsPlasma cells NeutrophilsNeutrophils EosinophilsEosinophils BasophilsBasophils MonocytesMonocytes

Leucocytes in loose supporting tissueLeucocytes in loose supporting tissueF-Fibroblasts, Er-Erythrocytes, N-Neurtrophils, Eo-Eosinophils, L-lymphocytes, P-F-Fibroblasts, Er-Erythrocytes, N-Neurtrophils, Eo-Eosinophils, L-lymphocytes, P-

Plasma cells, M-MacrophagesPlasma cells, M-Macrophages

Connective tissue cellsConnective tissue cells FibroblastsFibroblasts Histiocytes (Macrophages)Histiocytes (Macrophages) Plasma cellsPlasma cells Mast cellsMast cells Fat cellsFat cells

ADULT CONNECTIVE TISSUE COMPONENTS

Connective Tissue Cells

Connective tissue cellsConnective tissue cells

FibroblastsFibroblastsMost abundantMost abundantAppearance varies in relation to functional Appearance varies in relation to functional

statestateProduce connective tissue fibers & secrete Produce connective tissue fibers & secrete

ground substanceground substance

Mature FibroblastsMature Fibroblasts

Active fibroblastsActive fibroblasts

Histiocytes (Macrophages)Histiocytes (Macrophages) AbundantAbundant Inactive and active histiocytesInactive and active histiocytes Scavenger cellsScavenger cells Foreign body giant cellsForeign body giant cells Antigen presenting cellsAntigen presenting cells

MacrophageMacrophage

Plasma cellsPlasma cells Generally rare but numerous at certain Generally rare but numerous at certain

sites e.g., intestinal mucosa, lymphoid sites e.g., intestinal mucosa, lymphoid organsorgans

Nucleus—cart wheel appearanceNucleus—cart wheel appearance Production of antibodiesProduction of antibodies

Mast cellsMast cells Mast– well fed (German)Mast– well fed (German) Abundant in loose connective tissue Abundant in loose connective tissue

around blood vesselsaround blood vessels Secrete Heparin ( anticoagulant) Secrete Heparin ( anticoagulant) & Histamine (vasodilator)& Histamine (vasodilator)

Mast CellsMast Cells

Fat cells (adipocytes)Fat cells (adipocytes) Form adipose tissue when accumulate Form adipose tissue when accumulate

togethertogether Signet ring appearanceSignet ring appearance

Blue dotted lines - Blue dotted lines - AdipocytesAdipocytes

Orange Arrows - Fat Orange Arrows - Fat droplet "space"droplet "space"

Green Arrow - Nuclei Green Arrow - Nuclei of Adipocyteof Adipocyte

Connective tissue fibersConnective tissue fibers

Long slender protein polymers which are Long slender protein polymers which are found in differing proportions in various found in differing proportions in various types of connective tissuetypes of connective tissue

Predominant fiber type is responsible for Predominant fiber type is responsible for conferring specific properties to the tissue conferring specific properties to the tissue

Connective tissue fibersConnective tissue fibers Collagen fibers Collagen fibers --collagen--collagen Reticular fibers --collagenReticular fibers --collagen Elastic fiber -------elastinElastic fiber -------elastin

CollagenCollagen Long molecule—tropocollagenLong molecule—tropocollagen Three polypeptide chains intertwined Three polypeptide chains intertwined

together— together— triple helixtriple helix By now 19 varieties of collagen have been By now 19 varieties of collagen have been

identifiedidentified Most important & best studied are I,II, III, Most important & best studied are I,II, III,

IV &V.IV &V.

Growth of molecular character of a collagen fibrilGrowth of molecular character of a collagen fibril

Collegen fibers are most Collegen fibers are most abundant type of connective abundant type of connective

tissue fiberstissue fibers

Collagen fiber formation involves events Collagen fiber formation involves events that occur both within and outside the that occur both within and outside the fibroblastfibroblast

Collagen fibersCollagen fibers

Diameter (2-10 micrometer)Diameter (2-10 micrometer) Run randomly in various directionsRun randomly in various directions In many parts, collagen fibers lie parallel to In many parts, collagen fibers lie parallel to

each other forming bundles of various each other forming bundles of various sizessizes

Flexible but inelastic (non-extensible)Flexible but inelastic (non-extensible) Pink colour with H&E stainPink colour with H&E stain

Blue arrow - Collagen BundleBlue arrow - Collagen BundleGreen Arrow - Fibroblast nuclei Green Arrow - Fibroblast nuclei

Reticular fibersReticular fibers

Reticular fibers provide a supporting Reticular fibers provide a supporting framework for the cellular constituents of framework for the cellular constituents of various tissues and organsvarious tissues and organs

Reticular fibers are named for their Reticular fibers are named for their arrangement in a mesh-like pattern or arrangement in a mesh-like pattern or networknetwork

Reticular fibersReticular fibers Very thin branching fibers (rete—net)Very thin branching fibers (rete—net) Diameter (0.5 to 2 micrometer)Diameter (0.5 to 2 micrometer) Coating of proteoglycans & glycoproteins– Coating of proteoglycans & glycoproteins–

black colour with silver staining, red with black colour with silver staining, red with PASPAS

Abundant in connective tissue around Abundant in connective tissue around muscle fibers, nerve fibers, acini of glands, muscle fibers, nerve fibers, acini of glands, lymphoid organs & bone marrowlymphoid organs & bone marrow

Elastic fibersElastic fibers

Highly elastic can stretch one and half Highly elastic can stretch one and half time their original lengthtime their original length

Diameter (0.2 to 1.0 mic.m)Diameter (0.2 to 1.0 mic.m) Branch & rejoin to form loose networkBranch & rejoin to form loose network Found in lungs, large arteries, ligamenta Found in lungs, large arteries, ligamenta

flava (connecting laminae of successive flava (connecting laminae of successive vertebrae)vertebrae)

Elastin fibresElastin fibres

Ground substanceGround substance

Ground substace occupies the space Ground substace occupies the space between the cells and fibersbetween the cells and fibers

Ground substance consists largely of Ground substance consists largely of proteoglycans and hyaluronic acidproteoglycans and hyaluronic acid

Proteoglycans and Glycosaminoglycans Proteoglycans and Glycosaminoglycans (GAG) are responsible for the physical (GAG) are responsible for the physical properties of ground substanceproperties of ground substance

Embryonic connective tissueEmbryonic connective tissue

Develops from mesoderm & is known as Develops from mesoderm & is known as MesenchymeMesenchyme

Composed of star-shaped cells which lie in Composed of star-shaped cells which lie in an abundant relatively homogeneous an abundant relatively homogeneous intercellular substanceintercellular substance

Mucous tissueMucous tissue– Wharton’s jelly– Wharton’s jelly

Arrows = cells in mitosis; “C” = small blood vessels; Ground substance devoid of fibers; Cell processes extend into homogeneous ground substance

Disorders of connective Disorders of connective tissuetissue

Marfan syndromeMarfan syndrome - a genetic disease - a genetic disease causing abnormal fibrillincausing abnormal fibrillin

ScurvyScurvy - dietary deficiency in Vit.C leading - dietary deficiency in Vit.C leading to abnormal collagen.to abnormal collagen.

Ehlers-danlos syndromeEhlers-danlos syndrome - a genetic - a genetic disease causing progressive deterioration disease causing progressive deterioration of collagens affecting different sites in the of collagens affecting different sites in the body such as joints, heart valves & arterial body such as joints, heart valves & arterial wallswalls

Disorders of connective Disorders of connective tissuetissue

Osteogenesis imperfectaOsteogenesis imperfecta ( brittle bone ( brittle bone disease)disease) – insufficient production of good – insufficient production of good quality collagen to produce healthy, strong quality collagen to produce healthy, strong bonesbones

Spontaneous pneumothoraxSpontaneous pneumothorax – collapsed – collapsed lungs, believed to be related to subtle lungs, believed to be related to subtle abnormalities in connective tissueabnormalities in connective tissue