Fixation in Histopathology Lab

Fixation in Histopathology

• The primary goal of fixation is to preserve the tissue in its natural state, preventing degradation and decomposition, and allowing for accurate histological diagnosis.

Importance of Immediate Fixation

• Immediate fixation is critical to prevent autolysis, a process in which tissues degrade and break down due to enzymatic activity, leading to loss of tissue morphology and potential diagnostic errors.

Consequences of Improper Fixation

• Improperly fixed tissues can lead to artefacts, compromising the accuracy of histological diagnosis and potentially resulting in incorrect treatment.

Effects of Fixatives

• One of the effects of using fixatives is to cross-link proteins, preventing tissue degradation and maintaining tissue structure.

Role of Fixatives

• Fixatives help preserve tissues by denaturing proteins, preventing enzymatic activity, and maintaining tissue morphology.

Goals of Fixation

• The goal of fixation is not to kill microorganisms, but to preserve tissue morphology and prevent degradation.

Autolysis

• Autolysis is the process of self-digestion of tissues, resulting in degradation and loss of tissue morphology.

Optimal Fixation Conditions

• The optimal pH for fixation is close to neutrality, around 7.
• The usual osmolality range for fixation is 300-320 mmol/kg.
• Fixatives penetrate tissue at a rate of approximately 1 mm per hour.

Fixation in Electron Microscopy (EM) and Histochemistry

• The working temperature for fixation in EM and Histochemistry is around 4°C.

Fixation Timeframe

• Buffered formalin usually takes around 24-48 hours to completely fix tissues.