Chapter 3 Connective tissue

1.cells extracellular matrix 2. Fibers 3.Ground substance tissue fluid

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 CT dense CT adipose T reticular tissue

(2) CT in wide sense includes : cartilage bone blood

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

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

fibroblast fibroblast fibrocyte fibrocyte

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

EM: rich in a. lysosome b. Phagosome: phagocytosis c. Remnant d.  Microfilament and microtubule

a. Chemotaxis: chemotactic factor b. phagocytosis: ---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, complement and interleukin-I (IL-1)and interferon(INF) d.     antigen presenting function

③plasma 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

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 edema and contraction of SM Eosinophil chemotactic factor

Cytoplasm contain: slow reaction substance ---function: to 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 fibrocyte ---function: multidifferentiating potential

⑦leukocytes: neutrophil, acidophil and lymphocyte, ect.

2) fibers

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

EM: parallel-arranged fibrils 20-200nm in diameter Have periodic cross striation at 64nm interval

② elastic fiber (yellow fiber) LM: thinner and less, 0.2-1.0 um Slight red (HE) 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

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

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