Inflammation ( part 2) l General pathology revision for dental student

 Inflammation ( part 2) l General pathology revision

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Local Exudative Phenomenon

• The results of the vascular phenomenon are the escape of plasma fluid and WBCs from blood vessels into the interstitial tissue spaces forming the inflammatory exudate which consists of:                                                                                               

1.  Fluid component (fluid exudate)                                        
2.  Cellular component (cellular exudate)
3.  Fluid component (fluid exudate) 

Definition :

• Accumulation of extracellular protein-rich fluid at the area of inflammation.

Source:    

• Only from blood plasma.

Pathogenesis (causes of inflammatory edema)      

• ↑ vascular permeability (the main cause) due to contracted or damaged endothelium by the effect of toxins and chemical mediators.
• ↑ intra-capillary hydrostatic pressure: due to dilatation of arterioles & increased blood flow that pushes fluid outside capillaries.
• ↓ intra-capillary osmotic pressure: due to escape of plasma proteins from blood vessels to interstitial tissue.
• ↑ tissue osmotic pressure due to: 

1.     Extravascular escape of plasma proteins.
2.     Splitting of large necrotic tissue molecules into smaller ones.

• Obstruction of draining lymphatic vessels due to:

1.       fibrin thrombi (as fibrin is drained by lymphatics)              
2.       Acute lymphangitis.

Characters of the fluid exudate (inflammatory edema)?  

amount       

•     Depends on :

1. Site of inflammation: 

• Loose area as subcutaneous tissue of eye  lids allows accumulation of large amount of fluid exudate.
• while in solid tissue as inflammation of  bone, fluid exudate is scanty.

2. Nature of the irritant: e.g. excess in burns and allergic inflammation.

3. Lymphatic obstruction: by inflammation and fibrin thrombi delays drainage of exudate and leads to its accumulation.  

 

composition

1. High protein content (4-8 gm %)
2. Specific gravity is high (above 1018)
3. It clots on standing due to its fibrin content
4. It contains inflammatory cells.

Functions of exudate?    

• 1. Diluting the irritant especially chemical and bacterial toxins.
• 2. It brings antibodies to the site of inflammation.
• 3. High fibrinogen content often results in the formation of the fibrin which serves as:

1.      Barrier preventing spread of infection.
2.      Scaffolding for movement of leucocytes and repair cells , Surface phagocytosis.

• 4. Carries away waste products of cells and supplies their nutrition.
• 5. Phagocytic cells in the exudate.

         

Fate  

• fluid exudate is absorbed by lymphatics  , if exist bacteria → lymphadenitis , lymphangitis
• blood spread of bacteria through lymphatics → bacteremia , toxemia , septicemia , pyemia 

transudate:

• Fluid that finds its way into tissue spaces chiefly as a result of increased intravascular hydrostatic pressure

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