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
Download Presentation The PPT/PDF document "Connective tissue" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
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 tissueSlide6Slide7
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 CTSlide9Slide10Slide11Slide12Slide13
Elastic
fibresSlide14
Reticular connective tissueSlide15
Embryonic connective tissueSlide16
Specialized connective tissueSlide17
Collagen fibresSlide18Slide19Slide20
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 collagenSlide21Slide22Slide23
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.Slide30Slide31
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