Histology Terms - Self Assessment #1 Terms

1. Preservation

The process of maintaining tissue in a life-like state by preventing decay and autolysis. Usually achieved using chemical fixatives.

2. Hardening

A process that increases tissue firmness to facilitate cutting thin sections. Fixatives like formalin can harden tissue.

3. Solidification of Colloid Material

Occurs when colloid substances (e.g., mucus or cytoplasm) become more firm during fixation, allowing better structure retention.

4. Optical Differentiation

The ability to distinguish structures under a microscope, often enhanced by staining or fixation techniques.

5. Effect on Staining

Fixatives can impact how well tissues absorb stains. Good fixation improves staining by preserving cell structures and chemical components.

6. Mordant

A chemical that helps bind a dye to tissue, forming a dye-mordant complex. Common in histological staining (e.g., iron in hematoxylin staining).

7. Formaldehyde

A gas used as a tissue fixative (usually in solution as formalin). Preserves tissue by cross-linking proteins.

8. Formalin

A 37-40% aqueous solution of formaldehyde, typically diluted to 10% for tissue fixation. Standard fixative in histology.

9. Grossing

The process of examining and cutting tissue specimens into smaller pieces for processing and microscopic examination.

10. Infiltration

The process where tissues are permeated by embedding media (e.g., paraffin wax) to support tissue structure during sectioning.

11. Vacuum Infiltration

Infiltration done under vacuum conditions to enhance penetration of embedding media into the tissue, improving quality.

12. Microtome

An instrument used to cut extremely thin slices of tissue (sections) for microscopic examination.

13. Sectioning

The act of cutting tissue into thin slices (usually 3–5 microns) using a microtome after embedding in paraffin.

14. Tissue

Biological material composed of cells and extracellular components, forming organs and structures. Studied in histology for disease diagnosis.

15. Tissue Cassette

A perforated container used to hold tissue samples during fixation, processing, and embedding. Allows fluid circulation while keeping samples safe.

16. Water Bath

Used to float and flatten paraffin sections after sectioning. Typically maintained at 40–45°C.

17. Xylene

A clearing agent used in histology to remove alcohol from tissues before paraffin embedding. Also used to remove paraffin before staining.

18. Zenker’s Fluid

A mercury-based fixative containing mercuric chloride, potassium dichromate, and acetic acid. Provides excellent nuclear detail but is toxic and obsolete in many labs today.