Systematic vs Random Error Quiz

Study Notes

Artifacts in stained slides can result from various causes, including improper fixation, type of fixative, poor dehydration, improper reagents, or poor microtome sectioning.

Most cells and extracellular material are completely colorless, and to be studied microscopically, tissue sections must be stained (dyed).
Dyes stain material more or less selectively, often behaving like acidic or basic compounds.

Basic dyes, such as toluidine blue, alcian blue, and methylene blue, have an affinity for anionic components like nucleic acids and are termed basophilic.
Acid dyes, such as eosin, orange G, and acid fuchsin, stain acidophilic components like mitochondria, secretory granules, and collagen.

H&E is the most commonly used staining method, with hematoxylin staining DNA in the cell nucleus, RNA-rich portions of the cytoplasm, and the matrix of cartilage, producing a dark blue or purple color.
Eosin, as a counterstain, stains other cytoplasmic structures and collagen pink.

Trichrome stains, such as Masson trichrome, allow greater distinctions among various extracellular tissue components.
The periodic acid-Schiff (PAS) reaction stains carbohydrate-rich tissue structures, such as polysaccharides, distinctly purple or magenta.
The PAS reaction can be modified to specifically stain DNA in cell nuclei.
Lipid-rich structures can be revealed by avoiding lipid-removing processing steps and staining with lipid-soluble dyes like Sudan black.

Slide preparation, from tissue fixation to observation, can take from 12 hours to 2.5 days, depending on the size of the tissue, the embedding medium, and the method of staining.
The final step before microscopic observation is mounting a protective glass coverslip on the slide with clear adhesive.

With the bright-field microscope, stained tissue is examined with ordinary light passing through the preparation.
The microscope includes an optical system and mechanisms to move and focus the specimen.