Chapter 3 Chapter 3 Connective tissueConnective 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 proc

esses• 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 (1) CT in narrow sense means connetive

tissue proper which include:

loose CT dense CTadipose T reticular tissue

cartilage bone

blood

(2) CT in wide sense includes (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:functions: connection, supporting, d connection, supporting, defence and repairingefence and repairing

1)1) Cells: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 fibroblast 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（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 bacteri

um, virus and foreign cell

phagocytosis

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

c.  secretion: lysozyme（溶菌酶） , com

plement and interleukin-I (IL-1)and interf

eron(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

(chemotactic factor:

macrophage, leukocytes)

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.

neutrophil acidophil lymphocyte

2) fibers2) fibers

①collagenous fiber (white fiber)

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

EM: parallel-arranged fibrilsFibril: • 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（微纤维蛋白）

③reticular fiberLM: • 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, 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, mesenteriu

m---brown fat T: • fat cell contain many small lipid droplets,• rich in large mitochondria• centrally-located nucleus• rich in cap.• distribution: neonate

white fat Tbrown fat T

6.    reticular tissue---reticular cells: • stellate with processes-form network• round, ovoid and pale nucleus with 1-2 nucle

oli• EM: rich in RER---reticular fiber: connect to form network---distribution: hemopoietic tissue and lymphatic

tissue