In the described schedule, how long is the formalin fixation step applied for all stations?

• A. 15 minutes
• B. 2 hours
• C. 1 hour
• D. 30 minutes

Answer: (A)

The main idea is that fixation time is kept short and the same across all stations to ensure uniform preservation of tissue morphology. Formalin works by cross-linking proteins to halt cellular activity, but the duration matters: too long and you risk over-fixation, which can mask details and interfere with downstream steps; too short and you may get under-fixation and tissue degradation. In the described schedule, a brief, standardized 15-minute fixation is used because it provides enough cross-linking for small or thin specimens while keeping the workflow efficient and preventing over-fixation across stations. Longer times (like 1 hour, 30 minutes, or 2 hours) would increase the chance of over-fixation and slow down processing, whereas this 15-minute duration strikes a balance suitable for the described setup.