L3. Intro to Histology

Question 1

Name the 6 stages involved in obtaining a specimen for histological analysis.

Answer 1

1. Specimen collection
2. Fixation
3. Dehydration
4. Embedding
5. Sectioning
6. Staining

Question 2

Describe stage 1 - specimen collection.

Answer 2

Collection by :
punch biopsy (skin/oral)
needle biopsy (organs/skin lumps)
endoscopic biopsy (flexible tube, light and camera)

Question 3

Describe stage 2 - fixation.

Answer 3

Specimen is fixed using formaldehyde or glutaraldehyde.

Question 4

Describe stage 3 - dehydration.

Answer 4

Place the tissue in graded alcohols to remove water (60%, 70%, 80% etc)

Question 5

Describe stage 4 - embedding

Answer 5

Tissue is placed in xylene then paraffin wax or resin for support when sectioning)

Question 6

Describe stage 5 - sectioning.

Answer 6

Tissue is cut using a microtome (into single cell layers) to be mounted on glass slides.

Question 7

Describe stage 6 - staining.

Answer 7

Stains are not compatible with the supportive paraffin so it must be removed by xylene-> 100% ethanol -> 90% -> 80% -> 70% -> water.
Stain is then added.

Question 8

What does H and E stain do?

Answer 8

Stains acidic structures (eg nucleic acids) blue
Stains basic structures (eg cytoplasmic reticulum) red.
(opposite of pH chart).