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Chapter 3 Connective tissue. 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
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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
mesenchyme ---mesenchymal cell: /structure: • stellate 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
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
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
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
EM: • rich in RER,Golgi appatatus and free ribosome ---function: synthesize fibers and ground substance
Synthesis of collagenous fiber Three steps: a.synthesis of procollagen(RER) → process(Golgi) → out of cell b.procollagen→ tropocollagen → fibril c.fibril → collagenous fiber
*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
②macrophage ---structure: LM: • round or ovoid-irregular in shape when it have short blunt processes_pseudopodium • Small and dark nucleus • Acidophilic cytoplasm
EM: rich in • a.lysosome • b.Phagosome← phagocytosis and • pinosome ←pinocytosis • c.Remnant • d.Microfilament and microtubule
---function: a.Chemotaxis: chemotactic factor 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
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
③plasma cell ---structure: LM: • round or ovoid • Round eccentrically-located nucleus with more spot-liked heterochromatin • Basophilic cytoplasm
EM: rich in parallelly arranged RER, free ribosome and Golgi complex ---function: synthesize and secrete immunoglobulin, Ig-antibody
④mast cell ---structure: LM: • round and large cell • Small dark-stained nucleus • Basophilic secreting granules
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 ---function: cause allergic reaction
⑤fat 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
⑥undifferentiated mesenchymal cell ---structure:similar to fibrocyto ---function:multidifferentiating potential ⑦leukocytes: neutrophil,acidophil and lymphocyte
①collagenous fiber(white fiber) LM: • 1-20 um in diameter • Belt-liked wave and branch to form a network • Eosinophilic
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
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
③reticular fiber LM: • thin and less,0.2-1.0 um in diameter • Branch to form network • Argyrophilic fiber(silver impregnation method) EM: • type III collagen • 64nm cross striation ---distribution: • reticular tissue • connecting portion, e.g.reticular lamina
3) ground substance ---amorphous colloidal substance ---consists of proteoglycan, glycoprotein and tissue fluid
①proteoglycan-large molecular complex ---glycosaminoglycans: • chondroitin sulfate • keratin sulfate • dermatan sulfate • heparin sulfate • hyaluronic acid: 2.5um long --protein *molecular sieve
② glycoprotein: proteins ---fibronectin cells←fibronectin→collagen ↓ proteoglycan ---laminin ---chondronectin ---function: • Connection • affect the differentiation and movement of cells
③ tissue fluid tissue artery → Tissue fluid → vein →blood steam cells • dehydration • oedema
4.Dense connective tissue ---more fiber ---connection and supporting
1) regular DCT: • parallelly-arranged collagenous fibers • tendon cells: /special fibroblast /wing-liked processes ---distribution: tendons, ligament and cornea
2) irregular DCT: • Fiber arranged in bundles,runing in different direction • Fibroblast • less ground substance ---distribution: dermis, sclera and capsule of some organs
3) elastic T: • elastic fiber in bundles or in membrane • ligament and large artery
5.adipose tissue ---LCT+fat cells ---white fat T: • single fat cell • distribution in subcutaneous tissue, mesenterium ---brown fat T: • fat cell contain many small lipid droplets, • rich in large mitochondria • centrally-located nucleus • rich in cap. • distribution: neonate
6.reticular tissue ---reticular cells: • stellate with processes-form network • round, ovoid and pale nucleus with 1-2 nucleoli • EM: rich in RER ---reticular fiber: connect to form network ---distribution: hemopoietic tissue and lymphatic tissue