Chapter 11 



INFLAMMATION AND RELATED 

 PHENOMENA 



INFLAMMATION 



I 



nflammation is the local response of small blood vessels to in- 

 jury. It is characterised to the naked eye by redness, swelling, in- 

 creased heat and pain in the affected part. Microscopically it is 

 characterised by dilatation of arterioles, capillaries and venules, by 

 increased permeability of venules and capillaries to plasma protein 

 and by adhesion of leucocytes to the vascular endothelium and the 

 emigration of leucocytes into the tissues. Inflammation is a cyclical 

 reaction in which changes in vascular calibre and permeability 

 precede leucocyte emigration from vessels. The predominantly 

 polymorphonuclear exudate may be in turn replaced by lympho- 

 cytes, macrophages and sometimes plasma cells. The exudate may 

 then disappear, leaving the tissue normal once again or undergo 

 organisation in which there is replacement of the damaged area, 

 by collagen laid down by fibroblasts. 



The similarity of the inflammatory cycle in many different 

 species in response to many diverse types of injury, including 

 transient physical damage has led to the now generally accepted 

 view that the vascular events of inflammation are due at least in 

 part to the release or activation of local hormones or mediators 

 (see Spector, 1958). This hypothesis gained support from the dis- 

 covery of naturally-occurring substances with effects on small 

 blood vessels similar to those seen in inflammation. In recent 

 years the theory has been strengthened further by the demonstra- 

 tion of active forms of such compounds at the site of injury at the 

 time when they should be exerting their effect. Additional evi- 

 dence has been provided by the experimental suppression of in- 

 flammatory changes with the aid of specific inhibitors of com- 

 pounds suspected to be chemical mediators of these changes. 



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