Connective tissue
description
Transcript of Connective tissue
Connective tissue
What is connective tissue? As the name suggests, it connects the vari
ous 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 mesenchyme-embryonal 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 n
ucleoles 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
cells
extracellular
matrix
Major con
stituen
ts
Fiber
Ground substance
1) cells: seven types of cells are present in LCT
cells
of
CT
Fixed cells
Transient cells
Fibroblasts
Adipose cells
Mast cells Macrophage
s
Undifferentiated mesenchymal cell
Plasma cell
Blood cell
Macrophage
① fibroblast
---structure: LM: large,flattened cell with processes- stellate in sha
ped Large ovoid pale nucleus-contain more fine chro
matin, with clear one-two nucleoli Weakly basophilic cytoplasm-homogeneous
EM: rich in RER, Golgi appatatus and free riboso
me---function: synthesize fibers and ground substa
nce
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
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 、 I
FN (interferon) or interleukin) b. phagocytosis: Special phagocytosis: recognize Bacterium, vi
rus and foreign cell non special: carbon particles, dust and dead c
ells *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 with
more spot-liked heterochromatin 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 oedema and contraction of SM
Eosinophil chemotactic factor
Cytoplasm contain: leukotriene- slow reaction substance
Function: Mast cells degranulation r
esults in the release of histamine a
nd other vasoactive mediators whic
h induce the immediate hypersensit
ivity response (characteristic of urti
caria ( wheal-itch ) , allergic rhinit
is (sneeze) and asthma (cough)) an
d 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 fibrilsFibril: 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 brow
n(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 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
①proteoglycan Large molecular complex (polysac
charide)
---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 d
irection Fibroblast less ground substance---distribution: dermis, sclera and capsule of so
me 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, mesenteriu
m---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 nucle
oli EM: rich in RER---reticular fiber: connect to form network---distribution: hemopoietic tissue and lymphatic
tissue