Which process is used to preserve tissue before sectioning?

The preservation of tissue before sectioning is primarily achieved through fixation. This process involves treating the tissue with chemical agents that stabilize the cellular structure and proteins, effectively preventing autolysis (self-digestion) and decay. Common fixatives include formaldehyde, glutaraldehyde, and various alcohols, which cross-link proteins, thus helping to maintain the integrity of the tissue architecture for subsequent analysis.

Fixation is a critical step because it allows for the preservation of cellular morphology, making it possible for pathologists to make accurate diagnoses upon microscopic examination. Properly fixed tissues retain their structural context and biochemical properties, which is essential for later procedures such as embedding, staining, and acknowledging the tissue's cellular components.

While embedding, staining, and clearing are important processes in tissue preparation, they occur after fixation. Embedding involves infiltrating the fixed tissue with a medium to provide support for thin sectioning, while staining is used to enhance contrast in microscopy. Clearing, on the other hand, is a process that prepares the tissue for embedding by removing water, helping it to better absorb the embedding material. However, none of these processes can occur effectively without the prior step of fixation, which is foundational for the preservation of tissue integrity.