Chapter 3 Connective tissue Chapter 3 Connective tissue

1. General features: 1) small number of cells and large amount of extracellular ground substance 2) no polarity 3) all of them originate from mesenchyme - embryonic 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 (1) CT in narrow sense means connetive tissue proper which include: loose CTdense CT adipose Treticular tissue

cartilagebone blood (2) CT in wide sense includes :

3. Loose connective tissue (areolar tissue) consists of cells, fiber and ground substance features: have more types of cells and less fibers

functions: connection, supporting, defence and repairing

1)Cells:

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

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

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

fibrocyte fibroblast fibrocyte

② macrophage ---structure: LM: Round, ovoid or irregular in shape have short blunt processes: pseudopodium Small and dark nucleus Acidophilic cytoplasm

EM: rich in a. Lysosome （溶酶体） b. Phagosome: phagocytosis （吞饮作用） pinosome （吞饮体） : pinocytosis( 胞饮作用 ) c. Remnant d. Microfilament and microtubule

---function: a. Chemotaxis: chemotactic factor b. phagocytosis: (1)Special phagocytosis: recognize bacterium, virus and foreign cell phagocytosis

(2)non special phagocytosis: carbon particles, dust and dead cells

c. secretion: lysozyme （溶菌酶）, complement and interleukin-I (IL-1)and interferon(INF) d. antigen presenting function

③ plasma cell ---structure: LM: round or ovoid Nucleus with more spot-liked heterochromatin which located eccentrically Basophilic cytoplasm

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

④ mast 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 edema and contraction of SM Eosinophil chemotactic factor (chemotactic factor: macrophage, leukocytes)

Cytoplasm contain: slow reaction substance ---function: to cause allergic reaction

⑤ 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

⑥ undifferentiated mesenchymal cell ---structure: similar to fibrocyte ---function: multidifferentiating potential

⑦ leukocytes: neutrophil, acidophil and lymphocyte, ect. neutrophilacidophil lymphocyte

2) fibers

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

EM: parallel-arranged fibrils Fibril: nm in diameter Have periodic cross striation at 64nm interval

② elastic fiber (yellow fiber) LM: thinner and less, um Slight red (HE) branch and form a network EM: core: elastin-low electron density Peripheral: microfibril nm, electron dense ↑ fibrillin （微纤维蛋白）

③ reticular fiber LM: thin and less, 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

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, running in different direction Fibroblast less ground substance ---distribution: dermis, sclera and capsule of some organs

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

white fat T brown fat T

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