Chapter 3 Chapter 3

Connective tissueConnective tissue

1.     1.       General features:  General features: 1)   small number of cells and large amount of extracellular matrix (int1)   small number of cells and large amount of extracellular matrix (int

ercellular material)ercellular material)

2)  the extracellular matrix is composed of fibers and an amorphous gr2)  the extracellular matrix is composed of fibers and an amorphous ground substanceound substance

3)  all of them originate from 3)  all of them originate from mesenchymemesenchyme -embryonic CT -embryonic CT

4) functions: connection, supporting, protecting, nutrition, defense an4) functions: connection, supporting, protecting, nutrition, defense and repairingd repairing

2.2.    ClassificationClassification

• Connective tissue properConnective tissue proper

• CartilageCartilage

• BoneBone

• bloodblood

The types of CT are determined on the basis of the types of cell and the cThe types of CT are determined on the basis of the types of cell and the characteristics of the extracellular matrixharacteristics of the extracellular matrix

CT in narrow sense means CT in narrow sense means connective tissue properconnective tissue proper, incl, include:ude:

loose CTloose CT adipose tissueadipose tissue reticular tissuereticular tissue dense CTdense CT

Loose connective tissue (areolar tissue)Loose connective tissue (areolar tissue)• The most common type of connective tissueThe most common type of connective tissue

• consists of most types of cell and all the kinds of fibconsists of most types of cell and all the kinds of fibersers

• The most widely distributed in the bodyThe most widely distributed in the body

functions:functions: connection, supporting, defense and repairingconnection, supporting, defense and repairing

1)1) Cells:Cells:

① ① fibroblastfibroblast

------structure:structure: LM: LM: • large,flattened cell with processes, satellate in shalarge,flattened cell with processes, satellate in sha

pepe• Large ovoid pale nucleus - contain more fine chroLarge ovoid pale nucleus - contain more fine chro

matin, with clear one or two nucleolimatin, with clear one or two nucleoli• Weakly basophilic cytoplasmWeakly basophilic cytoplasm

EM:EM:• rich in rough endoplasmic reticulum (RER), Golgi rich in rough endoplasmic reticulum (RER), Golgi

complex and free ribosomecomplex and free ribosome

---function:---function: synthesis of fibers and ground substance synthesis of fibers and ground substance

fibrocytefibrocyte: still state or inactive fibroblast: still state or inactive fibroblast------structure:structure: • spindle-shaped, smallspindle-shaped, small• small, dark nucleussmall, dark nucleus• Acidophilic cytoplasmaAcidophilic cytoplasma

• EM: less organellesEM: less organelles

------function:function: become into become into fibroblast for repairingfibroblast for repairing

fibrocytefibrocyte fibroblastfibroblast

②②macrophagemacrophage---structure:---structure:

LM:LM:• Round, ovoid or irregular in shapeRound, ovoid or irregular in shape• have short blunt processes: pseudopodiumhave short blunt processes: pseudopodium• Small and dark nucleusSmall and dark nucleus• Acidophilic cytoplasmAcidophilic cytoplasm

EM: rich in EM: rich in •   lysosomelysosome• Phagosome: phagocytosisPhagosome: phagocytosis pinosome : pinocytosispinosome : pinocytosis• Residual bodiesResidual bodies• Microfilament and microtubuleMicrofilament and microtubule

---function:---function:

a.a.    Chemotaxis: chemotactic factor    Chemotaxis: chemotactic factor

b. b. phagocytosis:phagocytosis:

(1)Special phagocytosis:(1)Special phagocytosis: recognize bacterium, virus a recognize bacterium, virus a

nd foreign cellnd foreign cell

phagocytosis

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

c. c. Bioactive product Bioactive product secretion: lysozyme, cosecretion: lysozyme, co

mplement and interleukin-1 (IL-1)and interfmplement and interleukin-1 (IL-1)and interf

eron(INF)eron(INF)

d.d.    antigen presenting functionantigen presenting function

③③plasma cellplasma cell

---structure:---structure:

LM:LM:

• round or ovoid in shaperound or ovoid in shape

• Nucleus with more clock-liked heterochromatin Nucleus with more clock-liked heterochromatin which located eccentricallywhich located eccentrically

• Basophilic cytoplasmBasophilic cytoplasm

EM: rich in parallelly arranged RER, free ribosome and Golgi EM: rich in parallelly arranged RER, free ribosome and Golgi complexcomplex

---function:---function: synthesize and secrete immunoglobulin, Ig-antibod synthesize and secrete immunoglobulin, Ig-antibodyy

④④mast cellmast cell

---structure:---structure:

LM:LM:

• round and large cellround and large cell

• Small dark-stained nucleusSmall dark-stained nucleus

• Basophilic secreting granules--metachromaticallyBasophilic secreting granules--metachromatically

Basophilic secreting granulesBasophilic secreting granules:: • heparin: an anticoagulant heparin: an anticoagulant

• Histamine: increase vascular permeability, capillary Histamine: increase vascular permeability, capillary leakage to form edema, promotes the contraction of leakage to form edema, promotes the contraction of the smooth musclesthe smooth muscles

• Eosinophil chemotactic factorEosinophil chemotactic factor

• Other bioactive chemicalsOther bioactive chemicals

---function:---function: involved in al involved in allergic reactionlergic reaction

⑤⑤fat cellfat cell

---structure:---structure:

• large, round or polygonallarge, round or polygonal

• flattened ovoid nucleus located on one side of cellflattened ovoid nucleus located on one side of cell

• thin layer of cytoplasm thin layer of cytoplasm

• a large lipid droplet a large lipid droplet

---function:---function: synthesize and store fat synthesize and store fat

⑥⑥undifferentiated mesenchymal cellundifferentiated mesenchymal cell

---structure: similar to fibrocyte---structure: similar to fibrocyte

---function: multi-differentiating potential---function: multi-differentiating potential

• ⑦⑦leukocytesleukocytes: neutrophil, acidophil and lymph: neutrophil, acidophil and lymphocyteocyte

neutrophil acidophil lymphocyte

2) fibers2) fibers

①①collagenous fiber (white fiber)collagenous fiber (white fiber)

LM: LM: • 1-20 um in diameter1-20 um in diameter• Belt-liked wave and branch to form a networkBelt-liked wave and branch to form a network• EosinophilicEosinophilic

EM:EM: parallel-arranged fibrils parallel-arranged fibrils

Fibril: Fibril: • 20-200nm in diameter20-200nm in diameter• Have periodic cross striation at 64nm intervalHave periodic cross striation at 64nm interval

*formation of collagenous fibers:*formation of collagenous fibers:

collagen (type I and III) collagen (type I and III)

collagenous fibril collagenous fibril

collagenous fiber collagenous fiber

② ② elastic fiber (yellow fiber)elastic fiber (yellow fiber) LM: LM: • thinner and less, 0.2-1.0 umthinner and less, 0.2-1.0 um• Slight red (HE) Slight red (HE) • branch and form a networkbranch and form a network

EM:EM: • core: an amorphous substance--elastin-low electron densitycore: an amorphous substance--elastin-low electron density• Peripheral: microfibril 10-12 nm, electron densePeripheral: microfibril 10-12 nm, electron dense functionfunction rubber-like propertiesrubber-like properties

③③reticular fiberreticular fiberLM: LM: • thin and less,0.2-1.0 um in diameterthin and less,0.2-1.0 um in diameter• Branch to form a delicate networkBranch to form a delicate network• Argyrophilic fiberArgyrophilic fiber (stained by silver nitrate) (stained by silver nitrate)• PAS+PAS+

EM: EM:

• type III collagentype III collagen

• 64nm cross striation64nm cross striation

---distribution: ---distribution:

• reticular tissuereticular tissue

• connecting portion, e.g. reticular laminaconnecting portion, e.g. reticular lamina

3) ground substance3) ground substance

• amorphous colloidal substance, occupies space amorphous colloidal substance, occupies space between cells and fibers.between cells and fibers.

• Consists mostly of Proteoglycans and Hyaluronic Consists mostly of Proteoglycans and Hyaluronic acid. acid.

Proteoglycans Proteoglycans are very large molecules with a proteinare very large molecules with a proteincore and many long-chained polysaccharides core and many long-chained polysaccharides (glycosaminoglycans, GAGs) covalently bound to(glycosaminoglycans, GAGs) covalently bound to the core protein.the core protein.

GAGS:GAGS: Hyaluronic acidHyaluronic acid Heparan sulfateHeparan sulfate Chondroitin 4- and 6-sulfateChondroitin 4- and 6-sulfate HeparinHeparin Dermatan sulfateDermatan sulfate Keratin sulfateKeratin sulfate

Molecular sieve:Molecular sieve:

•The entangled macro-molecular proteoglycan aggregate forms The entangled macro-molecular proteoglycan aggregate forms a bottle brush-like structurea bottle brush-like structure

•To exclude or entrap molecules of different sizesTo exclude or entrap molecules of different sizes

•Serves as a physical barrier to prevent the spread of bacteria aServes as a physical barrier to prevent the spread of bacteria and other microorganisms.nd other microorganisms.

tissue fluidtissue fluid

Arterial end→ Tissue fluid → venous end →blood steamArterial end→ Tissue fluid → venous end →blood steam

oxygen, nutrientsoxygen, nutrients waste material, carbon dioxidewaste material, carbon dioxide cellscells

• Acts as the midium for exchange of metabolites between cirActs as the midium for exchange of metabolites between circulating and tissue cellsculating and tissue cells

4.4.        Dense connective tissueDense connective tissue

---more fiber---more fiber

---connection and supporting---connection and supporting

1) regular DCT1) regular DCT: :

• parallel-arranged collagenous fibersparallel-arranged collagenous fibers

• tendon cells: special fibroblasttendon cells: special fibroblast

---distribution: tendons, ligament and cornea---distribution: tendons, ligament and cornea

2) irregular DCT:2) irregular DCT:

• Fiber arranged in bundles, running in different directionFiber arranged in bundles, running in different direction• Less fibroblast and less ground substanceLess fibroblast and less ground substance• Form a three-dimensional network and to provide adequate Form a three-dimensional network and to provide adequate

resistance to stress from all directionsresistance to stress from all directions---distribution: dermis, sclera and capsule of some organs---distribution: dermis, sclera and capsule of some organs

5.5.              adipose tissueadipose tissue

---LCT + fat cells---LCT + fat cells• Fat cells from large aggregations and become the prinFat cells from large aggregations and become the prin

cipal cellscipal cells• Serves as metabolic energy reservoir, an insulating laServes as metabolic energy reservoir, an insulating la

yer to conserve body heatyer to conserve body heat

6.6.        reticular tissuereticular tissue---reticular cells:---reticular cells: • stellate with processes-form networkstellate with processes-form network• round, ovoid and pale nucleus with 1-2 nucleoliround, ovoid and pale nucleus with 1-2 nucleoli• EM: rich in REREM: rich in RER---reticular fiber:---reticular fiber: connect to form network connect to form network---distribution: hemopoietic tissue and lymphatic tiss---distribution: hemopoietic tissue and lymphatic tiss

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