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Connective tissue

Connective tissue. What is connective tissue? As the name suggests, it connects the various tissues of the body and gives them support. 1.       General features: 1)   small number of cells and large amount of extracellular ground substance

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Connective tissue

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  1. Connective tissue

  2. What is connective tissue? • As the name suggests, it connects the various tissues of the body and gives them support.

  3. 1.       General features: 1)   small number of cells and large amount of extracellular ground substance 2)  extracellular is composed of fibers and amorphous ground substance-matrix 3)   all of them originate from mesenchyme-embryonal CT 4) have functions of connection, supporting, protecting, nutrition, defence and repairing

  4. mesenchyme ---mesenchymal cell: /structure: • stellate/star in shaped with processes • a large nucleus,with clear nucleoles • slight basophilic cytoplasm /function: a.    undifferentiated cell b. multiple developmental potential→CT cell, SM and endothelial cell ---matrix

  5. 2.Classification ---CT in narrow sense means connetive proper which include loose CT, dense CT, adipose T and reticular tissue ---CT in wide sense includes cartilage, bone and blood

  6. 3.Loose connective tissue(areolar tissue) • features: have more types of cells and less fibers • functions: connection, supporting, defence and repairing • consists of cells, fiber and ground substance

  7. Major constituents cells Fiber extracellular matrix Ground substance

  8. cells:seven types of cells are present in LCT

  9. Fibroblasts Adipose cells Mast cells Macrophages Undifferentiatedmesenchymal cell Fixed cells cells of CT Plasma cell Blood cell Macrophage Transient cells

  10. ① fibroblast ---structure: LM: • large,flattened cell with processes- stellate in shaped • Large ovoid pale nucleus-contain more fine chromatin, with clear one-two nucleoli • Weakly basophilic cytoplasm-homogeneous

  11. EM: • rich in RER, Golgi appatatus and free ribosome ---function: synthesize fibers and ground substance

  12. Synthesis of collagenous fiber Three steps: a.synthesis of procollagen(RER) → process(Golgi) → out of cell b.procollagen→ tropocollagen → fibril c.fibril → collagenous fiber

  13. *fibrocyte: still state or inactive fibroblast ---structure: • spindle-shaped, small • N:small,dark stained • Acidophilic cytoplasma • EM: less organelles ---function: become into fibroblast for repairing

  14. EM: RER Golgi

  15. ②macrophage ---structure: LM: • round or ovoid-irregular in shape when it have short blunt processes_pseudopodium • Small and dark nucleus • Acidophilic cytoplasm

  16. EM: rich in • a.lysosome • b.Phagosome← phagocytosis and • pinosome ←pinocytosis • c.Remnant • d.Microfilament and microtubule

  17. ---function: a.    Chemotaxis: chemotactic factor(TNFα、 IFN (interferon) or interleukin) b. phagocytosis: • Special phagocytosis: recognize Bacterium, virus and foreign cell • non special: carbon particles, dust and dead cells *Phagosome(pinosome) + primary lysosome →secondary lysosome →remnants

  18. c.secretion: lysozyme, complement and interleukin-I (IL-1)and interferon(INF) b.antigen presenting function: *capture antigen→processes→+ MHC II molecule (major histocompatibility complex molecules) →antigen-MHC II complexes→ TLC/BLC

  19. ③plasma cell ---structure: LM: • round or ovoid • Round eccentrically-located nucleus with more spot-liked heterochromatin • Basophilic cytoplasm

  20. EM: rich in parallelly arranged RER, free ribosome and Golgi complex ---function: synthesize and secrete immunoglobulin, Ig-antibody

  21. ④mast cell ---structure: LM: • round and large cell • Small dark-stained nucleus • Basophilic secreting granules

  22. Basophilic secreting granules: • heparin:an anticoagulant • Histamine: cause cap. permeability↑, cap. leakage to form oedema and contraction of SM • Eosinophil chemotactic factor Cytoplasm contain: • leukotriene- slow reaction substance

  23. Function: Mast cells degranulation results in the release of histamine and other vasoactive mediators which induce the immediate hypersensitivity response (characteristic of urticaria（wheal-itch）, allergic rhinitis (sneeze) and asthma (cough)) and anaphylactic shock.

  24. ⑤adipose cell(fat cell) ---structure: • large, round or polygonal • flattened ovoid nucleus located on one side of cell • thin layer of cytoplasm • a large lipid droplet ---function: synthesize and store fat

  25. This is a higher magnification of fat cell with a large lipid droplets and cytoplasm pushed to the periphery membrane, nucleus is flattened against the membrane also.

  26. ⑥undifferentiated mesenchymal cell ---structure:similar to fibrocyto ---function:multidifferentiating potential ⑦leukocytes: neutrophil,acidophil and lymphocyte

  27. 2) fibers

  28. ①collagenous fiber(white fiber) LM: • Main fiber • 1-20 um in diameter • Belt-liked wave and branch to form a network • Eosinophilic

  29. EM: parallel-arranged fibrils Fibril: • 20-200nm in diameter • Have periodic cross striation at 64nm interval *formation: Extracellular polymerize collagen(type I and III) →collagenous fibril → collagenous fiber

  30. ② elastic fiber (yellow fiber) LM: • thinner and less, 0.2-1.0 um • Slight red(HE), purple(aldehyde fuchsin) or brown(orcein) • Branch and form a network EM: • core: elastin-low electron density • Peripheral: microfibril 10-12 nm, electron dense ↑ fibrillin

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