Preparatory Stage: Decalcification
Before proceeding to staining the histological slide, the hard material must be properly prepared. Bone tissue has a high density due to massive deposition of inorganic compounds.
To ensure the specimen can be sectioned and thoroughly examined under a microscope, a decalcification procedure is performed. This process involves softening the bone using various acids. Exposure to an acidic environment leads to the dissolution and complete removal of calcium salts from the matrix, while the organic framework of the tissue retains its original structural integrity. Without this step, adequate identification of microscopic elements would be impossible.
Specifics of Schmorl's Method
The primary tool for revealing fine bone tissue elements in this case is Schmorl's stain. A thionine solution is used as the main staining agent.
Thionine interacts with specific tissue components, providing clear contrast for various zones of the specimen. The main target for this dye is the collagen lining that covers the internal surfaces of microscopic spaces within the bone. It is precisely due to the selective binding of thionine to the collagen fibers in these zones that Schmorl's method is considered the standard for demonstrating the architecture of bone cavities.
Interpretation of the Microscopic Picture
The classic object for study using this method is a long bone. When examining a prepared slide under a light microscope, the following picture is visualized:
- Dark brown color: The walls of bone cavities (so-called lacunae) and the walls of the tiniest canaliculi branching from them are stained in this saturated shade. The intense coloration is due to the presence of the collagen lining.
- Light brown color: Serves as the background of the specimen. The extracellular matrix of the bone tissue is stained in this paler shade.
Morphologically, a whole system of interconnected structures is clearly visible on the slide. First and foremost, these are the bone cavities themselves, which in living tissue serve as housings for cells—osteocytes. A network of bone canaliculi radiates from these lacunae. Cellular processes are located within these narrow pathways. Visually, this entire complex is perceived as characteristic dark branching structures standing out contrastingly against the light brownish background of the extracellular matrix.