Which fixative is commonly used for connective tissue in histology?

• A. Bouin Solution
• B. Zamboni fixative
• C. Osmium tetroxide
• D. Orth Solution

Answer: (A)

Bouin's fixative is favored for connective tissue because its components rapidly penetrate and cross-link proteins in a way that preserves collagen fibers and the overall architecture of the extracellular matrix. The combination of formaldehyde, acetic acid, and picric acid stabilizes delicate connective tissue structures and enhances their appearance under common stains, especially trichrome stains used to highlight collagen. After fixation, thorough washing is important to remove residual picric acid, which can otherwise affect staining or compatibility with downstream steps. In contrast, osmium tetroxide is mainly used for lipid preservation and electron microscopy, Zamboni fixative emphasizes antigen preservation for certain immunohistochemistry applications, and Orth solution is not specifically optimized for connective tissue staining, making Bouin’s the most reliable choice for this purpose.