It is true about formalin –
**Formalin and Fixation**
**Core Concept**
Formalin, a solution of formaldehyde in water, is commonly used as a fixative in pathology to preserve tissues and prevent decay. The process of fixation is crucial for maintaining the structural integrity of tissues, allowing for accurate histological examination and diagnosis.
**Why the Correct Answer is Right**
The correct answer will be related to the mechanism of fixation, which involves the cross-linking of proteins and the covalent binding of formaldehyde to amino groups. This process stabilizes the tissue structure and prevents degradation, making it suitable for histopathological examination. Formalin fixation also involves the fixation of nucleic acids, which is essential for molecular pathology.
**Why Each Wrong Option is Incorrect**
* **Option A:** Formalin is not used for preserving blood samples, as it can cause hemolysis and interfere with laboratory tests.
* **Option B:** Formalin is not a disinfectant, although it has some antimicrobial properties, making it less effective than other disinfectants.
* **Option C:** Formalin is not used for preserving tissues for transplantation, as it is not suitable for maintaining the viability of cells and tissues.
**Clinical Pearl / High-Yield Fact**
Remember that formalin fixation is essential for maintaining tissue architecture and allowing for accurate histopathological examination. It is also used as a fixative in molecular pathology to preserve nucleic acids.
**Correct Answer:** D