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CT CELLS.pptx
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- 2. • INTRODUCTION • COMPONENTS •FUNCTIONS • CONNECTIVE TISSUE CELLS • CONNECTIVE TISSUE FIBERS
- 3. INTRODUCTION • Connective tissueare defined as those composed predominantly of intercellular material that is extracellular matrix which is secreted by the connective tissue cells. • The cells are therefore usually widely seperated by their matrix, which is composed of fibrous protein & a relatively amorphous ground substance.
- 4. • The termconnective is applied to a tissue that fills the interstices between more specialised elements. • It is found in almost every part of the body • It is conspicuous in some regions & scanty in others
- 5. Connective Tissue Cells Extracellularmatrix Fibres Ground substance -Collagen -Elastic -Reticular -Proteoglycans -Glycoproteins -Glycosaminoglycans CONNECTIVE TISSUE COMPONENTS Resident cells Wandering cells -Fibroblasts -Undifferentiated mesenchymal cells -Adipocytes -Pigment cells -Macrophages -Mast cells -Lymhocytes -Plasma cells -Other leukocytes
- 6. FUNCTIONS • Connect, Bind,Support, Strengthen the tissues • Protects and insulates internal organs • Major transport system • Energy reserve and insulation against heat loss • Repair as in wound healing • Regeneration of tissues • Defense of the body
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- 8. CONNECTIVE TISSUE CELLS RESIDENTCELLS WANDERING CELLS •FIBROBLASTS •UNDIFFERENTIATED - MESENCHYMAL CELLS •ADIPOCYTES •PIGMENT CELLS •MACROPHAGES •MAST CELLS •LYMPHOCYTES •PLASMA CELLS •NEUTROPHILS •EOSINOPHILS •BASOPHILS •MONOCYTES
- 9. RESIDENT / INTRINSIC/ PERMANENT / FIXED CELLS
- 10. 1.FIBROBLASTS • Principal cellof connective tissue • Synthesis of collagen, reticular & elastic fibers & the complex carbohydrates of the ground substance • Reside in close proximity to collagen fibers so called fixed cells
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- 16. RETICULOCYTE/ RETICULAR CELLS •Fibroblasts secreting reticular fibers • Reticular tissue: Fibrocellular network of fibroblasts & delicate collagenous fibers • Seen in liver, kidney, spleen & most lymphoid tissues
- 17. Myofibroblasts • H&E: bundlesof actin filament with actin motor proteins- nonmuscle myosin • Expression of α- smooth muscle actin is regulated by TGF-β1 • Fibronexus • Mechanotransduction system
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- 19. Role of myofibroblastsin wound repair • Blood clot= fibrin+ blood cells • 1-2 days: neutrophils & monocytes • 3 days: macrophages replace neutrophils • Role of fibroblasts & vascular endothelial cells • 5 days: Granulation tissue bridges the incision gap • Fibroblats exert tractional forces on ECM
- 20. • Fibroblasts differentiateinto myofibroblast under the influence of TGF-β1 & mechanical forces • Myofibroblasts generate & maintain steady contractile force shortening of connective tissue fibers & wound closure • 2nd week: Connective tissue scar
- 21. Abnormalities in woundrepair • Hypertrophic scar • keloid • Palmar fibromatosis ( Dupuytren’s disease)
- 22. 2. UNDIFFERENTIATED MESENCHYMAL CELLS (MESENCHYMALSTEM CELLS) • Seen in Embryonic connective tissue • Various elements of mature connective tissue are derived from mesenchymal stem cells
- 23. • As morespecialised cells are formed they lose their ability to transform into other types. Eg: fibroblasts
- 24. 3. ADIPOCYTES (Lipocytes/ Fatcells) • Differentiated from mesenchymal stem cells • Central large fat globule(unilocular): Glycerol esters of oleic, palmitic & stearic acids • Store neutral fat, produce a variety of hormones, inflammatory mediators & growth factors • Store chemical energy
- 25. H & ESUDAN III
- 26. FUNCTIONS: • Control Energybalance & lipid homeostasis • Endocrine role: Adipokine secretion • Mobilization of fat is under nervous & hormonal control • No new adipose tissue is thought to form after the immediate postnatal period
- 27. Brown fat: • Multilocularadipose tissue • Metabolize fatty acids & generate heat • Uncouple cellular respiration via the mitochondrial uncoupling protein (UCP1) • PET scan: supraclavicular, in the neck & along the spine • Beige fat cell: Distinct type of thermogenic fat cell, thought to be derived from precursor cells in white fat
- 29. 4. PIGMENT CELLS •Cells containing a brown pigment (usually melanin) in their cytoplasm • Sites: →iris & choroid of eyeball →epidermis of skin • Cells of 2 types: 1. Melanocytes 2. Melanophores/ Chromatophores
- 30. MELANOCYTE • Synthesize melanin •Neural crest origin MELANOPHORE/CHROMATOPHORE • Engulf pigment released by other cells • Modified fibroblasts
- 31. • The fibroblasts& blood vessels within healing wounds develop from mesenchymal stem cells associated with the tunica adventitia of venules
- 32. MIGRANT / WANDERING/ RELATED / FREE CELLS
- 33. MACROPHAGES (TISSUE HISTIOCYTES/CLASMATOCYTES) • Derivedfrom monocytes & contain abundant lysosomes • Phagocytose Trypan blue, India ink & Lithium carmine • Lysosomes: Acid phosphatase activity • L/M: evidence of phagocytic activity • TEM: Surface exhibits numerous folds & finger like projections
- 35. • Phagocytic, digestive& secretory functions • Secretion: immune response, anaphylaxis & inflammation • Antigen presenting cells MHC II interact with helper CD4 T lymphocytes • Arrive 24 hours after occurance of injury • Mode of action: Phagocytosis & immune response reactions
- 36. M1 Macrophages (Classically activatedmacrophages) • Promote inflammation, destruction of ECM & apoptosis • Elicit chronic inflammation & tissue injury • Foreign body giant cells/ Langhans cells
- 37. M2 macrophages (Alternatively activatedmacrophages) • Activated by IL-4,5,10,13 • Anti- inflammatory, proliferative & angiogenic • Resolution of inflammation & promote wound repair • Efficient at combating parasitic infections: Schistosomiasis • Involved in pathogenesis of allergy & asthma
- 38. Mononuclear phagocyte system (MPS) •Primarily derived from monocytes • Phagocytose Trypan blue & India ink • Cells become fixed in specific tissues & may adopt a variety of morphologic appearances. • Functions: phagocytosis, secretion of lymphokines, antigen processing & antigen presentation • Exception: Microglia, Osteoclasts & Fibroblasts
- 39. MAST CELLS • Developin bone marrow & differentiate in connective tissue • 20-30µm in diameter • Gluteraldehyde fixation toluidine blue Metachromatic staining of granules (heparin) • The mast cell is related to the basophil that it contain similar granules • Cell surface: high affinity Fc receptors (Fc£RI)
- 40. • Granule components: •Heparin, histamine, tryptase, superoxide dismutase, aryl sulphatase, β-hexosaminidase & chymase
- 41. METACHROMASIA • When componentsof a cell or tissue stain in a colour different from that of the dye used, the staining is said to be metachromatic.
- 42. MAST CELLS MCTC MASTCELLS/ CONNECTIVE TISSUE MAST CELLS MCT MAST CELLS/ MUCOSAL MAST CELLS TRYPTASE & CHYMASE TRYPTASE SKIN INTESTINAL SUBMUCOSA BREAST AXILLARY LYMPH NODES GRANULES: LATTICE-LIKE GRANULES: SCROLL LIKE LUNGS INTESTINAL MUCOSA
- 43. MCTC MAST CELLS •In the vicinity of small blood vessels, hair follicles, sebaceous glands & sweat glands & in the capsules of organs • Exception: central nervous system • Exception: Spleen
- 44. BASOPHILS • Develop &differentiate in bone marrow • Share many features with mast cells: basophilic secretory granules, similar mediators & high affinity Fc receptors • Don’t produce PGD2 & IL-5
- 45. LYMPHOCYTES •Principally involved in immuneresponses •Thin rim of cytoplasm & heterochromatic nucleus
- 46. PLASMA CELLS • Antibodyproducing cells derived from B lymphocytes • Prominent consituent in loose connective tissue: GI & respiratory tracts • short life span: 10-30 days • H&E: cartwheel / analog clock face
- 49. •Produce large amounts ofonly one type of protein- a specific antibody •Produced antibodies are discharged locally or stored within the cell •Antibodies stored within the cell form inclusons called Russell’s bodies
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- 52. CONNECTIVE TISSUE FIBERS •The most conspicuous components of connective tissue are the fibers within it • They provide strength & support to the connective tissue • 3 types: Collagen Reticular Elastic
- 53. 1. COLLAGEN FIBERS •Most abundant structural components of the connective tissue • 28 different types • Seen in bundles • Bundles may be straight or wavy • Bundles often branch or anastomose with adjacent bundles
- 54. PHYSICAL PROPERTIES • Flexible& have high tensile strength • Pliable & can bend easily • Birefringence • Swell & become soft when treated with weak acid/ alkali • On boiling converted to gelatin
- 55. COLLAGEN FIBRILS • 8-12nmdiameter • Osmium staining: 65nm- banding pattern • Collagen molecule/ Tropocollagen is the subunit AFM
- 56. Collagen molecule/ Tropocollagen •300nm long & 1.5nm thick • Head to tail alignment in overlapping rows • Covalent bonds between the collagen molecules of adjacent rows gives tensile strength • Triple helix of 3 intertwined polypeptides known as α chains
- 57. α chains • Varyin size from 600-3000 aminoacids • 42 types of α chains • Encoded by different genes • 29 types of collagen: Roman numerals I – XXIX • Collagen molecule can be Homotrimeric / Heterotrimeric
- 58. TYPE IV COLLAGEN TYPEIV COLLAGEN • Short filaments that form sheets • seen in basal lamina, kidney glomeruli & lens capsule • Collagenopathy: Alport’s syndrome
- 59. RETICULAR FIBERS • Supportingframework- liver, kidneys, bone marrow, spleen & other lymphoid organs • Consist of collagen fibrils- type III • 65nm banding pattern • 20nm diameter • Exhibit branching pattern • Do not form bundles
- 60. Staining properties • H& E • Periodic acid- Schiff reaction(PAS) • Silver staining procedures: Gomori & Wilder methods Argyrophilic
- 61. ELASTIC FIBERS • Runsingly, branch & anastomose with each other • Thinner than collagen • But thick bunbles in ligamentum flava & ligamentum nuchae • Interwoven with collagen fibers
- 62. Staining properties • H& E • Orecin / Resorcin-fuchsin • Aldehyde fuchsin • Verhoeff’s method
- 63. • Produced by:fibroblasts, smooth muscle cells,… • Elastic property is related to its unusual polypeptide backbone, which causes random coiling • Composed of Central core of elastin Fibrillin microfibrils
- 64. ELASTIN • 70KDa • Hydrophobic •Desmosine & Isodesmosine • Encoded by one of the largest genes: 28kilobases, less than 10% encodes elastin
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