Histology and Its Methods: Part II

Question 1

“Doing histology” requires a _________ with a specimen and a microscope

Answer 1

Slide

Question 2

What is the major problem facing scientists studying tissues?

Answer 2

As soon as a tissue is removed from a living organism, it begins to degrade due to bacterial destruction and cellular self-digestion

Question 3

What two processes contribute to cellular degeneration?

Answer 3

1. Bacterial destruction
2. Cellular self-digestion

Question 4

To study tissues in their most natural states, what must occur?

Answer 4

Steps must be taken to inhibit destruction and preserve the tissue

Question 5

Why must tissues and organs be sectioned for study?

Answer 5

Because tissues and organs are too thick for light from a light microscope to pass directly through them

Question 6

What are the major steps to preparing a tissue for study?

Answer 6

The tissue sample is

1. Removed
2. Fixed
3. Dehydrated
4. Cleared
5. Infiltrated
6. Embedded

Question 7

It can take anywhere from ___ hours to ___ days to prepare a slide from tissue fixation to observation

Answer 7

12 hours

2.5 days

Question 8

What factors result in the significant differences in time regarding tissue preparation?

Answer 8

Tissue size, embedding medium, and staining method

Question 9

A _________________ is a solution of stabilizing or cross-linking compounds that inactivate degrading enzymes

Answer 9

Fixative

Question 10

What’s a common fixative for light microscopy?

Answer 10

Formalin

Question 11

What’s a common fixative for electron microscopy?

Answer 11

Glutaraldehyde

Question 12

After fixation, what occurs during the preparation of tissues for study?

Answer 12

Dehydration

Question 13

How does tissue dehydration occur?

Answer 13

Water is gradually extracted by transfers through a series of more concentrated alcohol (ethanol) solutions, eventually ending in 100%

Question 14

What occurs during clearing?

Answer 14

Ethanol is replaced by an organic solvent of alcohol and embedding medium, resultuing in a translucent appearance

Question 15

What’s the step called when a tissue is placed in melted parafin at 58 degrees celsius or snap frozen in liquid nitrogen?

Answer 15

Infiltration

Question 16

After infiltration, what occurs during tissue slide preparation?

Answer 16

Embedding

Question 17

________________ is the process by which the tissue is placed in a small mold contraining melted parafin and then allowed to harden

Answer 17

Embedding

Question 18

Hardened block with tissue and surrounding embedding medium is trimmed and placed for sectioning in a ___________________

Answer 18

Microtome

Question 19

During sectioning, tissues are sliced according to needs. Sections are sliced between 3 and 10 micrometers for _______ microscopy and less than one micrometer for _________ microscopy

Answer 19

Light

Electron

Question 20

Why must tissue sections be sliced smaller for electron microscopy than light microscopy?

Answer 20

Because electrons have a much smaller wavelength and can’t penetraten through thicker sections

Question 21

What’s the final step of tissue preparation?

Answer 21

Sections are placed on glass slides and stained for light microscopy or metal grids for electron microscopy

Question 22

What’s the most common type of stain?

Answer 22

Hematoxylin and eosin

Question 23

Hematoxylin stains cellular components with a negative charge, like nucleic acids that have an affinity for positively charged (basic) dyes, otherwise called _________________

Answer 23

Basophilic

Question 24

Which H&E staining component stains negative cellular components?

Answer 24

Hematoxylin

Question 25

Cellular components with a positive charge, like proteins with amino groups, stain with eosin, making these cellular components ______________

Answer 25

Acidophilic

Question 26

Hematoxylin binds ___ charges; eosin binds ___ charges

Hematoxylin stains _____; eosin stains _____

Answer 26

Negative; positive

Purple; pink

Question 27

Which component of H&E staining serves as the counterstain?

Answer 27

Eosin

Question 28

Why are counterstains useful?

Answer 28

Because staining procedures often label only specific structures, rendering parts of the cell invisible

Question 29

________________ staining contains three colored components to allow for greater distinction among extracellular tissue components

Answer 29

Masson trichrome

Question 30

In Masson Trichrome staining, what types of cellular components are stained?

Answer 30

Extracellular matrix

Question 31

In Masson trichrome staining, collagen-rich ECM stains _____, cytoplasm stains _____, and nuceli stain ______

Answer 31

Blue

Pink

Red/purple

Question 32

___________________ stains negatively charged, sulfate-containing glycans, usually mucins or glycosaminoglycans

Answer 32

Alcian blue

Question 33

_____________ stains neutral glycans

Answer 33

Peridic acid Schiff

Question 34

_______________________ uses solutions of silver salts to visualize ECM fibers and nervous tissue elements

Answer 34

Metal impregnation

Question 35

What type of stain is shown?

Answer 35

Masson trichrome

Question 36

What type of stain is shown?

Answer 36

Alcian blue

Question 37

What type of stain is shown?

Answer 37

Metal impregnation

Question 38

DAPI stains __________________ the color ________

Answer 38

Nucleic acids

Blue

Question 39

In _______________ sections, specimens are cut along the direction of the organ

Answer 39

Longitudinal

Question 40

In _____________ sections, specimens are cut perpendicular to the length of the organ

Answer 40

Cross/transverse

Question 41

In _________________ sections, specimens are cut at an angle between cross and longitudinal sections

Question 42

Why are sections often examined in parallel (serial sections)?

Answer 42

Because sections are limited to two-dimensionality, representing only a part of a larger three-dimensional structure

Question 43

Distortion in preparatory steps may result in structural abnormalities called _______________, structures seen microscopically that may differ from structures present when tissue was alive

Answer 43

Artefacts

Question 44

What are five problems that can result during tissue preparation and in turn distort slide interpretation?

Answer 44

1. Shrinkage, resulting in artificial spaces
2. Loss of molecules, like lipids, glycogen, and other low molecular weight substances often lost during fixation
3. Wrinkles of a section
4. Stain precipitates
5. Differential staining (it’s impossible to stain all tissue components on a slide)