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Tissue Fixation
Fixation of tissues suspends autolysis and also bacterial degradation of tissues and cells. It is used so that tissue specimens may be stored for a period of time to allow both gross and histological examination. Commonly formalin is used to fix tissues because it rapidly diffuses into the tissue and suspends the processes of autolysis.
Routine tissue fixation relies on the diffusion of formalin through tissue and is therefore impeded in thick tissue blocks. In blocks of tissue which are too thick, autolytic processes may continue for a long period of time before the cells in the centre become fixed. As a result histological sections of the tissue may be unsatisfactory because autolytic changes obscure many morphological characteristics of cell injury and necrosis that may have occurred antemortem.
Therefore it is best to take small thin sections of tissue (approximately 1cm thick) for fixation and histological sectioning.
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Veterinary Pathology - Autolysis