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Connective tissue Connective tissue

Connective tissue - PowerPoint Presentation

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Connective tissue - PPT Presentation

Seema Zargar Most diverse and abundant tissue Main classes Connective tissue proper Cartilage Bone tissue Blood Characteristics Mesenchyme as their common tissue of origin mesenchyme ID: 246415

collagen tissue connective elastin tissue collagen elastin connective elastic cross protein tropoelastin lysine tropocollagen proline glycine structure amino residues

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Slide1

Connective tissue

Seema

ZargarSlide2

Most diverse and abundant tissue

Main classes

Connective tissue properCartilageBone tissueBloodCharacteristicsMesenchyme as their common tissue of origin (mesenchyme derived from mesoderm)Varying degrees of vascularityNonliving extracellular matrix, consisting of ground substance and fibers Cells are not as abundant nor as tightly packed together as in epithelium

Connective tissueSlide3

Enclose organs as a capsule and separate organs into layers.

Areolar

Connect tissues to one another. Tendons and ligaments.Support and movement. Bones.Storage. FatInsulation. Fat.Transport. Blood.Protection. Bone, cells of the immune system.Functions of connective tissueSlide4

Ground substance – unstructured material that fills the space between

cells

Fibers – collagen, elastic, or reticularCells – fibroblasts, chondroblasts, osteoblasts, hematopoietic stem cells, and others.Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content.Structural Elements of Connective TissueSlide5

Connective tissue can be classified into three

categories

:proper,embryonic, specializedClassification of Connective tissueSlide6
Slide7

Subclassifications

of C.T(proper)Slide8

Embryonic: Is further divided into

mesenchyme

and mucoid.Specialized: Is further divided into bone, cartilage and blood.Connective tissue proper: Is further divided into elastic tissue, reticular tissue, adipose tissue, areolar (loose tissue) and dense tissue.Sub classifications of CTSlide9
Slide10
Slide11
Slide12
Slide13

Elastic

fibresSlide14

Reticular connective tissueSlide15

Embryonic connective tissueSlide16

Specialized connective tissueSlide17

Collagen fibresSlide18
Slide19
Slide20

Collagen is rich in

proline

and glycine, both of which are important in the formation of the triple-stranded helix. Proline facilitates the formation of the helical conformation of each αchain because its ring structure causes “kinks”in the peptide chain. Glycine, the smallest amino acid, is found in every third position of the polypeptide chain. It fits into the restricted spaces where the three chains of the helix come together. The glycine residues are part of a repeating sequence, -Gly–X–Y–, where X is frequently proline and Y is often hydroxyproline(but can be hydroxylysine,). Most of the α-chain can be regarded as a polytripeptide whose sequence can be represented as (–Gly–Pro–Hyp–) Structure of collagenSlide21
Slide22
Slide23

Collagen biosynthesis

Endoplasmic Reticulum

mRNA attached to ERprotein synthesized into ER lumencotranslational and post-translational modifications3 proto-a-chains form soluble procollagenmoved to golgi apparatusGolgi Apparatuspacked into secretion vesiclesfuse with membraneOutside Cellprocollagen processed by enzymes outside cellassemble into collagen fiberscollagen fibrils form lateral Interactions of triple helicesSlide24

Collagen biosynthesisSlide25

Tropocollagen

as the basic structural unit of Collagen

Tropocollagen has a mass of about 285 kdal and consist of three polypeptide chains. Tropocollagen -280 nm long -head & tail region30% glycine, 30% proline& hydroxyproline re-aggregate -native collagen (64nm)non Covalent hydrogen bonding between the three αchain is via hydroxyproline.tropocollagenpolarized in fiber, 1/4 staggered array –period accounted for by gaps fall in dark bandsSlide26

Staggered array of

tropocollagen

MoleculesCollagen fibres exhibit crosssstriations every 640A. The length of the tropocollagenmolecule s 2800A.There is a gap of 400oA between the end of one tropocollagenand the start of another. This gap play an important role in mineralization process. Slide27

Tropocollagen structureSlide28

Tropocollagen stabilizationSlide29

Lysyl

oxidase is an extracellular copper enzyme that catalyzes formation of aldehydes from lysine residues in collagen and elastin precursors. These aldehydes are highly reactive, and undergo spontaneous chemical reactions with other lysyl oxidase-derived aldehyde residues, or with unmodified lysine residues. This results in cross-linking collagen and elastin, which is essential for stabilization of collagen fibrils and for the integrity and elasticity of mature elastin.Complex cross-links are formed in collagen called Pyridinoline which is derived from three lysine residues.Slide30
Slide31

Stability of the collagen helix™

The temperature at which half of the helical structure is lost is called the melting temperature™.

The Tm of tropocollagenis a criterion of the stability of its helical structure. Tm depends on the body temperature of the source species. collagens from icefishhas the lowest Tm while warm blooded animals have the highest Tm. This difference in thermal stability is correlated with the contents of iminoacid (prolineand hydroxyproline) in the collagen. The higher the iminoacid content , the more stable the helix. Tm of (pro-pro-Gly) is 24C while poly (Pro-Hyp-Gly) is 580C indicating hydroxylation stabilizes triple helix. The experiments using αα\-bipyridylan iron chelatorwhich inhibit hydroxylation shows that without hydroxylation triple helix formation does not occur. Slide32

Collagenase

and its types

Source: Clostridium histolyticumI.U.B.: 3.4.24.3Crude collagenase preparations contain not only several collagenases but also a sulfhydryl protease, clostripain, a trypsin-like enzyme, and an aminopeptidase. This combination of collagenolytic and proteolytic activities is effective at breaking down intercellular matrices, the essential part of tissue dissociation. One component of the complex is a hydrolytic enzyme which degrades the helical regions in native collagen preferentially at the Y-Gly bond in the sequence Pro-Y-Gly-Pro- where Y is most frequently a neutral amino acid. This cleavage yields products susceptible to further peptidase digestion. Crude collagenase is inhibited by metal chelating agents such as cysteine, EDTA or o-phenanthroline but not DFP. It is also inhibited by α2-macroglobulin, a large plasma glycoprotein. Ca2+ is required for enzyme activity. Particular enzymatic profiles of each collagenase have been correlated with the tissues from which the cells for study were obtained (or with the uses to which the cells are put) and as a result of the correlations several types of crude

collagenases

have been established by Worthington: Types 1, 2, 3, and 4.Slide33

 Type 1 crude

collagenase

has the original balance of collagenase, caseinase, clostripain and tryptic activities. Type 2 contains higher relative levels of protease activity particularly clostripain. Type 3 contains lowest levels of secondary proteases.Type 4 is designed to be especially low in tryptic activity to limit damage to membrane proteins and receptors.Slide34

Elastin compositionSlide35

Elastin

Elastin

 is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched. Elastin is also an important load-bearing tissue in the bodies of vertebrates and used in places where mechanical energy is required to be stored. In humans, elastin is encoded by the ELN gene.Slide36

Composition of

elastin

Elastic fiber is composed of the protein fibrillin and elastin made of simple amino acids such as glycine, valine, alanine, and proline.Elastin is made by linking many soluble tropoelastin protein molecules, in a reaction catalyzed by lysyl oxidase, to make a massive insoluble, durable cross-linked array. The amino acid responsible for these cross-links is lysine. Tropoelastin is a specialized protein with a molecular weight of 64 to 66 kDa, and an irregular or random coil conformation made up of 830 amino acids.Desmosine and isodesmosine are types of links for the tropoelastin molecules.Slide37

Tissue distribution

Elastin

serves an important function in arteries as a medium for pressure wave propagation to help blood flow and is particularly abundant in large elastic blood vessels such as the aorta. Elastin is also very important in the lungs, elastic ligaments, the skin, and the bladder, elastic cartilage. It is present in all vertebrates above the jawless fish.Slide38

Biosynthesis of elastinSlide39

Structure

protein

Mr 64 to 66 kDacomposed of the amino acids glycine, valine, alanine, and prolinecross-linked tropoelastin monomersfirst secreted as soluble precursors (tropoelastin)assembly and crosslinking of tropoelastin monomersform insoluble elastin matrix into functional fibreslysine residues in the cross-linking domain of secreted tropoelastin rapidly cross-linked (both inter- and intra-molecularly by lysyl oxidase)hydrophobic segments - elastic propertiesα-helical segments (alanine- and lysine-rich) - form cross-links between adjacent molecules