2: Staining

Give the 4 steps to stain tissue

Fixation

Embedding

Sectioning

Staining

Hematoxylin & Eosin?

most common

Alcian blue?

stains mucins blue

massons trichrome?

stains nuclei blue

collagen green

keratin red/pink

Van gieson?

nuclei blue

collagen red

cytoplasm yellow

giemsa?

nuclei dark blue

cyto pale blue

Fixation?

Used to avoid tissue digestion and to preserve tissue morphology and molecular composition. Chemical substances used to preserve tissues = fixatives, e.g. formaldehyde

Embedding

To obtain thin sections, tissues must be infiltrated with embedding substances that give a rigid consistency to the tissue, making tissues more resistant to sectioning. Embedding materials include paraffin and plastic resins

Dehydration?

Replaces tissue water with organic solvents, water extracted by bathing tissue in graded series of ethanol and water

Clearing?

As tissues become infiltrated with solvent, usually become transparent (= clearing), this
step runs consecutively with dehydration step.

Sectioning?

Small blocks containing tissues are sectioned on microtomes using steel or glass blade