Download 3-Connective tissue

Connective tissue
 What

is connective tissue?
As the name suggests, it connects the
various tissues of the body and gives them
support.
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 mesenchymeembryonal CT
4)
have functions of connection, supporting,
protecting, nutrition, defence and repairing
mesenchyme
---mesenchymal cell:
/structure:

stellate/star 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
---CT in narrow sense means connetive
proper 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
Major constituents
cells
extracellular
Fiber
matrix
Ground substance
1) cells:
seven types of cells are present in LCT
Fibroblasts
Fixed cells
Adipose cells
Mast cells
cells
Macrophages
of
Undifferentiated mesenchymal cell
CT
Plasma cell
Transient cells
Blood cell
Macrophage
① fibroblast
---structure:
LM:
 large,flattened cell with processes- stellate in
shaped
 Large ovoid pale nucleus-contain more fine
chromatin, with clear one-two nucleoli
 Weakly 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
procollagen(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
EM:
RER
Golgi
②macrophage
---structure:



LM:
round or ovoid-irregular in shape when it
have short blunt processes_pseudopodium
Small and dark nucleus
Acidophilic cytoplasm





EM: rich in
a. lysosome
b. Phagosome← phagocytosis and
pinosome ←pinocytosis
c. Remnant
d. Microfilament and microtubule
---function:
a.
Chemotaxis: chemotactic factor(TNFα、
IFN (interferon) or interleukin)
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/BLC
③plasma cell
---structure:
LM:
 round or ovoid
 Round eccentrically-located nucleus
more spot-liked heterochromatin
 Basophilic cytoplasm
with
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:
Mast cells degranulation
results in the release of histamine
and other vasoactive mediators
which induce the immediate
hypersensitivity
response
(characteristic of urticaria（whealitch）, allergic rhinitis (sneeze) and
asthma (cough)) and anaphylactic
shock.
⑤adipose cell(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
This is a higher
magnification of fat
cell with a large
lipid droplets and
cytoplasm pushed to
the periphery
membrane, nucleus
is flattened against
the membrane also.
⑥undifferentiated mesenchymal cell
---structure:similar to fibrocyto
---function:multidifferentiating potential
⑦leukocytes: neutrophil,acidophil and
lymphocyte
2) fibers
①collagenous fiber(white fiber)
LM:
 Main fiber
 1-20 um in diameter
 Belt-liked wave and branch to form a network
 Eosinophilic
EM: parallel-arranged fibrils
Fibril:
 20-200nm in diameter
 Have 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 um
 Slight red(HE), purple(aldehyde fuchsin) or
brown(orcein)
 Branch and form a network
EM:
 core: elastin-low electron density
 Peripheral: microfibril 10-12 nm, electron dense
↑
fibrillin

Physical properties:

As their name implies elastic fibers can
be stretched (like a rubber band ) and
return to their original length when
tension is released.
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
①proteoglycan
Large
molecular
(polysaccharide)
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:
 Connection
 affect the differentiation and movement of
cells
③ tissue fluid
tissue
artery → Tissue fluid → vein →blood steam
cells
 dehydration
 edema
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
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 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
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