Histology Techniques

Question 1

What is histology?

Answer 1

Microscopic anatomy

Question 2

What factors can affect resolution?

Answer 2

-Wavelength of light
- Numerical apeture (the ability of a lens to gather light + resolve a point at a fixed distance from the lens)
-Reflective index of mounting media (slower speed of light= better resolution)

Question 3

What is the goal of fixation?

Answer 3

-To imobilize components to maintain structura relationships
-Prevent autolysis
-Firm up structures to allow sectioning

Question 4

What five factors can affect fixation?

Answer 4

1. Time until tissue is placed in fixative
2. Fixative volume (min of 10 parts formalin)
3. Fixation time
   4.Tissue thickness
4. Tissue type

Question 5

What do you need to do if the sample contains calcification?

Answer 5

You must decalcify it after it has been fixed. For this we would use a strong acid

Question 6

Define basophilia

Answer 6

blue color resulting from basic dye binding to negative charge

Question 7

Define eosinophilia

Answer 7

Pink color resulting from acidic dye binding to positive charges

Question 8

How would something look if stained with H&E?

Answer 8

Hematoxylin (H): Imparts blue color to acidic components like DNA and RNA and some cellular secretions
Eosin (E): Imparts pink to red color to basic components like the cytoplasm and extracellular products

Question 9

What is a romanovsky stain? How does it differ from H&E? Examples?

Answer 9

It is a combination of eosin and methylene blue
It differs from H&E because methylene blue stains deeper blue and can result in metachromasia

Question 10

Define metachromasia

Answer 10

characterized by a shift in the normal color of the dye (blue) to a metachromatic color in the presence of highly acidic (polyanionic) substances

• highly basophilic stains can exhibit this phenomena (toluidine blue and methylene blue)

Question 11

Describe Periodic Acid-Schiff (PAS), what does it stain for?

Answer 11

A histochemical procedure used to identify intra- and extra- cellular carbohydrates, that particularly contain adjacent glycol linkages
Step 1: tx with periodic acid
Step 2: Stain aldehyde groups w/ schiff stain (will appear magenta)

Question 12

Describe silver impregnation methods

Answer 12

Used to demonstrate different structures, target structures stain black.

Question 13

Describe elastic fiber stains

Answer 13

Used to highlight elastic fibers in connective tissues. Stain black

Question 14

Describe trichrome stain

Answer 14

Used to enhance connective tissue elements

Question 15

Describe acid fast stain

Answer 15

Used to identify different types of organisms

Question 16

Describe different artifacts and processing errors

Answer 16

-artifacts resulting from antemortem procedures
-change in cell volume due to fixation and/or dehydration
- inactivation of most enzymes and some antigenic molecules
-no fats/lipids after processing leaving vacules
-air bubbles under tissues
-dull blade
-wrinkling of tissue
-knife chatter
-plane of section

Question 17

What is immunohistochemistry?

Answer 17

“staining” with antibody against a specific molecule used to label that molecule in a tissue section

Question 18

What is Electron Microscopy? And what is its benefits over other types of staining?

Answer 18

“stained” with heavy metals. Accelerated electrons are the source of illumination, and provides better magnification + resolution. Able to visualize cellular organelles+ macromolecules

Question 19

What two cellular organelles are basophilic?

Answer 19

The nucleus and ribosomes

Question 20

What two cellular organelles are basophilic?

Answer 20

The nucleus and ribosomes

Question 21

What two cellular organelles are eosinophilic?

Answer 21

Mitochondria and the Smooth ER

Question 22

Define Heterochromatin

Answer 22

Highly condensed chromatin in which genes are NOT expressed. Found consistently in marginal chromatin, nucleolar associated, karyosomes ( discrete clumps of chromatin)

Question 23

Define euchromatin

Answer 23

Uncoiled chromatin w active DNA. Properties of these chromatic vary between cell types and their metabolic activity

Question 24

How can you determine if a cell is more metabolically active?

Answer 24

There is more euchromatic vs heterochromatin

Question 25

Define static cell type

Answer 25

No longer capable of division

Question 26

Define stable cell type

Answer 26

Will undergo periodic division to maintain normal function

Question 27

Define continuously dividing cell type

Answer 27

Constant dividing i.e skin, intestinal, and bone marrow

Question 28

What are the two types of cell death?

Answer 28

Necrosis: “cell murder” the cell bursts and causes an inflammatory reaction
Apoptosis: programmed cell death. Cell shrinks, blebs into fragments. NO inflammatory reaction associated with it.