A damaged tissue shows extremely dark purple staining when cut, and the knife dulled quickly. What is the cause?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

The main idea here is how decalcification affects the ability to cut and stain calcified tissue. When tissue contains calcium salts, it must be softened before embedding and sectioning. If decalcification is incomplete, the mineralized matrix keeps the tissue hard. That hardness makes microtomy difficult, so the knife dulls quickly and sections are rough or tear easily. The dense mineralized areas can also influence staining, often producing very dark, intense purple regions because hematoxylin binds strongly to basophilic structures in those mineral-rich areas and doesn’t penetrate or differentiate as cleanly as in properly decalcified tissue. Extending the decalcification to remove the calcium salts yields sections that cut smoothly and stain with more normal contrast. Over-decalcification, by contrast, tends to wash out details and yield paler, less distinct staining, not the observed extremely dark appearance.