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

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 pot

ential→CT cell, SM and endothelial cell

---matrix

2.       Classification ---CT in narrow sense means connetive prop

er 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) cells: seven types of cells are present in LCT

① fibroblast

---structure: LM:

large,flattened cell with processes- stellate in shapedLarge ovoid pale nucleus-contain more fine chromatin, with clear one-two nucleoliWeakly 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 procol

lagen(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_pseudopodiumSmall and dark nucleusAcidophilic cytoplasm

EM: rich in a.  lysosomeb. Phagosome← phagocytosis and pinosome ←pinocytosisc.  Remnantd.  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 ovoidRound eccentrically-located nucleus with more spot-liked heterochromatinBasophilic 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

2) fibers

①collagenous fiber(white fiber)

LM: 1-20 um in diameterBelt-liked wave and branch to form a networkEosinophilic

EM: parallel-arranged fibrilsFibril:

20-200nm in diameterHave 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 umSlight red(HE), purple(aldehyde fuchsin) or brown(orcein)Branch and form a network

EM: core: elastin-low electron densityPeripheral: microfibril 10-12 nm, electron dense

↑ fibrillin

③reticular fiberLM:

thin and less,0.2-1.0 um in diameterBranch to form networkArgyrophilic fiber(silver impregnation method)

EM: type III collagen64nm cross striation

---distribution: reticular tissueconnecting 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:

Connectionaffect 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 directionFibroblastless 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 celldistribution in subcutaneous tissue, mesenterium

---brown fat T: fat cell contain many small lipid droplets,rich in large mitochondriacentrally-located nucleusrich in cap.distribution: neonate

6.    reticular tissue---reticular cells:

stellate with processes-form networkround, ovoid and pale nucleus with 1-2 nucleoliEM: rich in RER

---reticular fiber: connect to form network---distribution: hemopoietic tissue and lymphatic

tissue