Grossly many inflammatory processes (eg: response to viral or bacterial infection) in the URT will begin as a serous discharge, and then progress to a catarrhal exudate, and then to purulent/pseudomembranous/haemorrhagic as neutrophils are recruited
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Grossly many inflammatory processes (eg: response to viral or bacterial infection) in the URT will begin as a serous discharge, and then progress to a catarrhal exudate, and then to purulent/pseudomembranous/haemorrhagic as [[Neutrophils - WikiBlood|neutrophils]] are recruited