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Connective Tissue

Connective Tissue. Course : Microanatomy (SCAN 213) For : Pre-medical students II Time : 2 h Date : October 31,2001 Lecturer: Dr. Prapee Sretarugsa Department of Anatomy Faculty Of Science Mahidol University Tel : 201- 5424 E-mail : scpsr@mahidol.ac.th . Objectives.

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Connective Tissue

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  1. Connective Tissue Course : Microanatomy (SCAN 213) For : Pre-medical students II Time : 2 h Date : October 31,2001 Lecturer: Dr. Prapee Sretarugsa Department of Anatomy Faculty Of Science Mahidol University Tel : 201- 5424 E-mail : scpsr@mahidol.ac.th

  2. Objectives • : After you have studied this lecture, you should be able to • Explain the components of connective tissue • Describe the structures and functions of all types of cells in connective tissue • Identify all fibers in connective tissue as well as their localization in the organs • Explain the composition of ground substance as well as its function • Classify the type of connective tissue

  3. Connective Tissue (CT) • Derives from mesoderm • Mesenchyme pleuripotency) • Mesenchymal cells can differentiate into • - connective tissue • - bone, cartilage • - blood and hemopoietic cells • - lymphoid cells

  4. Characteristic of Connective Tissue • Consists of a large amount of extracellular matrix with a limited number of cells

  5. Extracellular Matrix (ECM) • A complex of nonliving macromolecules • synthesized by the cells • Some tissue consists of small amount of ECM • Connective tissue contains a large amount of • ECM with a limited number of cells • A major component of connective tissue • proper • Comprises of • - Ground substance – resists forces of • compression • - Fibers – provides tensile force

  6. Ground Substance • Consists of • Glycosaminoglycans (GAGs) • Proteoglycans • Adhesive glycoproteins

  7. Properties of GAGs • Long, inflexible, unbranched polysaccharides • High negative charge • Repeating disaccharide units • One of repeating unit is amino sugar which is sulfated (SO-3) • Second sugar is uronic acid with a carboxyl gr. (COO-) • Retension of positive ions (eg. Na+) together with water, maintaining tissue architecture turgor which tend to prevent deformation by compressive force

  8. Structure of GAGs • Disaccharide units form covalent linkage with protein to form proteoglycans • Proteoglycans attach to hyaluronic acid • Hyaluronic acid, nonsulfated GAG

  9. Types of GAGs

  10. Struture ofProteoglycan • Macromolecues formed by sulfated GAGs form covalent bonds with a protein core • Structures look like a bottle brush • Each proteoglycan is covalently linked to hyaluronic acid forming huge macromolecules, Aggrecan aggregates

  11. Proteoglycans • Macromolecues formed by sulfated GAGs form covalent bonds with a protein core • Structures look like a bottle brush • Each proteoglycan is covalently linked to hyaluronic acid forming huge macromolecules, Aggrecan aggregates

  12. Functions of Proteoglycans • Resist compression and retard the rapid movement of microorgani and metastatic cells • Form molecular filter (in association with basal lamina) of varying pore sizes and charge distributions that selectively screen and retard macromolecules as they pass through them • Contain binding sites of certain signaling molecules eg. TGF-ß

  13. Functions of Proteoglycans and Hyaluronan during development • Epithelial branching and differentiation • Eye development • Limb development

  14. Adhesive Glycoproteins Large macromolecules have several domains - at least one domain usually bind to integrins - one to collagen fibers - one to proteoglycans

  15. The Major Types of Adhesive Glycoproteins • Fibronectin • Laminin • Entactin • Tenascin • Chrondronectin • Osteonectin

  16. The Binding Sites of Adhesive Glycoproteins Fibronectin - collagen, heparin, heparan sulfate, hyaluronic acid, integrin Laminin - stricly limited to the basal lamina - heparan sulfate, type IV collagen, entactin & cell membrane Entactin - laminin, type IV collagen Tenascin - integrin, proteoglycan & fibronectin - distribution is limited to embryonic tissue

  17. The Binding Sites of Adhesive Glycoproteins Chrondonectin - type II collagen, chrondroitin sulfate, hyaluronic acid, & integrins of chondroblast and chrondocyte Osteonectin - type I collagen, integrins of osteoblast and osteocyte

  18. Integrin

  19. Fibers • Provide tensile strength and elasticity to ECM • Can be classified into 3 types based on their • morphology and reactivity with dyes • - Collagen • - Reticular • - Elastic

  20. Collagen Fibers • Collagen, constitue about 20% of all the body • proteins • Form a flexible fiber whose tensile strength • is greater than that of stainless steel of • comparable diameter • White fiber, colorless • No specific staining for collagen fiber • Acidophilic fiber • EM showing cross-banding at regular interval of 67 nm

  21. Components of collagen fibers • Smaller subunits, tropocollagen • Formed from parallel aggregates the thinner • fibril 10 to 300 nm in diameter

  22. Tropocollagen • 280 nm long • 1.5 nm in diameter • Three polypeptide chains, a-chains • - formed triple helical configuration • - each chain contains about 1,000 aa • - every third aa is glycine • - the majority of the remaining aa is • proline, hydroxyproline,hydroxylysine

  23. Six Major types of collagen • Types Characteristics • I Most common type collagen ,thick • fiber • II Forms slender fiber in hyalin and elastic • cartilages • III Reticular fiber • - Highly glycosylated, thin fiber0.5-2.0 um • - Rich coating of sugar likely stained with • silver salt (Argyrophilic fiber) • - positively stained with periodic acid - • schiff (PAS) reaction

  24. Six Major types of collagen Types Characteristics IV Do not display 67 nm periodicity Forms a meshwork of procollagen molecules V Forms very thin fibrils and association with Type I VI Forms small aggregates, anchoring fibrils

  25. Elastic Fibers • Slender, long and branching in loose CT • Form coarse bundles in ligament • (ligamentum flavum) and fenestrated sheet • (concentric sheet in the wall of large a.) • Elastin,a protein rich in glycine and proline • - unusual aa, Desmosine & Isodesmosine • - a high degree of elasticity • - forms a core of elastic fiber • Microfibrils (10 nm in diameter, glycoprotein, • fibrillin), located at the periphery of elastin

  26. Elastic fibers A. Elastin has a random coil structure in the relax state, but reforms as a different random coil on relaxation B. Elastin molecule are covalently linked into arrays which can reversibly stretch and recoil, and may be arranged as fibers or sheets • Elastic fibers are composed of • microfilaments surrounding and • organizing core region of cross- • linked elastin

  27. Blood vessel, showing the elastic fibers Elastic f.

  28. Tunica media of aorta Show the typical wavy appearance of thick bundles of elastic fiber

  29. Reticular fibers • Collagen type III • Frame work of lymphoid organs, liver ect. • Highly glycosylated, thin fiber0.5-2.0 um • Rich coating of sugar likely stained with silver salt (Argyrophilic fiber) • Positively stained with periodic acid - schiff (PAS) reaction

  30. Cellular components of CT • Fixed cells • - A resident population of cells have developed • and remain within CT • - fibrobasts, mast cells, adipose cells, pericytes • & macrophages • Wandering (Transeint) cells • - Originate mostly in bone marrow • - plasma cells, lymphoctes, neutrophils, • eosinophils, basophils, monocytes, and some • macrophages

  31. Fibroblasts - Produce ECM & Fibers - Active fibroblasts often reside with collagen bundles - Elongated, fusiform cells & pale-staining cytoplasm - Large ovoid nuclei with prominent nucleoli - EM, showing prominent RER, Golgi complex - Inactive, Fibrocytes ; small, elongate & deeply stained nuclei - Some movement

  32. Fibroblasts and Fibrocytes Fibroblasts Fibrocytes

  33. Fibroblasts, showing euchromatic nucleus, prominent RER Collagen fibers RER Collagen fibers

  34. Myofibroblasts - Modified fibroblasts contain actin and myosin filaments - Surface profile of nucleus resembles smooth m. - Basal lamina is absent - Abundant in wound healing area (purse string effect) • - Contribute to retraction and shrinkage of scar tissue

  35. SEM : Pericytes - Undifferentiated mesenchymal cells - As named adventitial cells or perivascular cells - Locate around capillaries and venules - Possess characteristic of smooth muscle cells and endothelial cells

  36. TEM : Pericytes - Their basal lamina are directly continuous with basal lamina of endothelial cell - EM, cytoplasmic characteristics almost identical with endothelial cells - In large venules, they have characteristic of smooth m. cells Capillary P Pericyte

  37. Wound healing - New connective tissue & blood vessels are formed - Undifferentiated mesenchymes lacated in tunica adventitia of venules and small veins - Fibroblast - Pericytes - Endothelial cells

  38. Macrophages - They function in removing cellular debris (phagocytosis) and protceting body against foreign invaders - They also play a role in presenting antigens to lymphocytes - They are about 10-30 um in diameter - Cell surface is uneven - Basophilic cytoplasm, many small vacuoles, small dense granules- - Indented nucleus - EM showing prominent Golgi app. & RER, abundant lysosomes

  39. Macrophage • Under chronic inflammatory condition • They congregate, enlarge and become polygonal-shaped epitheloid cells • If the particulate matter is excessive large, several macrophages may fuse to form a Foreign-body giant cell • Macrophage residing in CT, Fixed Macrophage (resident Macrophage) • Free Macrophage - migrate from the blood

  40. Macrophage

  41. Macrophage Development and Distribution • Histologist once believed that macrophages were derived from precursor cells in Reticuloendothelial System, which included nonphagocytic cells • Presently, all members of phagocytotic cells arise from a common stem cell in bone marrow, possess lysosomes, can phagocytose and display Fc receptors and receptors for complement, as classified to as Mononuclear Phagocyte System

  42. Macrophage Development and Distribution • Macrophages localized in certain regions of the body were given specific names before their origin was understood. • Kupffer cells of the liver • Dust cells of the lung • Langerhans cells of the skin • Monocytes of the blood • Macrophages of CT, spleen, lymph node, thymus and bone marrow • Osteoclast of the bone • Microglia of the brain

  43. Mast cells • Oval shape with round or oval nucleus • 20-30 um in diameter • Abundance of the large basophilic granule • Granules showMetachromasia • Granules containing histamine, heparin, eosinophil chemotactic factor (ECF), nutrophil chemotactic factor (NCF), chondroitin sulfate protease, aryl sulfatase

  44. Mast cells • Oval shape with round or oval nucleus • 20-30 um in diameter • Abundance of the large basophilic granule • Granules showMetachromasia

  45. Mast cells • Granules showMetachromasia

  46. Mast Cell • Granules containing histamine, heparin, eosinophil chemotactic factor (ECF), nutrophil chemotactic factor (NCF), chondroitin sulfate protease, aryl sulfatase

  47. Plasma cells • Found in large numbers in area of chronic inflammation • Derived from B lymphocyte • Ovoid cells, 10-20 um, eccentric nucleus • Short life span of 2-3 weeks • Intensely basophilic cytoplasm, prominent RER • Spherical nucleus consisted of heterochromatin radiating out from the center, look like clockface appearance in LM observation • Produce circulating antibodies (r-globulin)

  48. Plasma cells • Found in large numbers in area of chronic inflammation • Derived from B lymphocyte • Ovoid cells, 10-20 um in diameter, Eccentric nucleus

  49. Plasma Cell • Intensely basophilic cytoplasm, prominent RER • Produce circulating antibodies (r-globulin) • Spherical nucleus consisted of heterochromatin radiating out from the center, look like clockface appearance in LM observation

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