Histology and Its Methods: Part II Flashcards

1
Q

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

A

Slide

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2
Q

What is the major problem facing scientists studying tissues?

A

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

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3
Q

What two processes contribute to cellular degeneration?

A
  1. Bacterial destruction
  2. Cellular self-digestion
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4
Q

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

A

Steps must be taken to inhibit destruction and preserve the tissue

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5
Q

Why must tissues and organs be sectioned for study?

A

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

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6
Q

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

A

The tissue sample is

  1. Removed
  2. Fixed
  3. Dehydrated
  4. Cleared
  5. Infiltrated
  6. Embedded
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7
Q

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

A

12 hours

2.5 days

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8
Q

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

A

Tissue size, embedding medium, and staining method

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9
Q

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

A

Fixative

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10
Q

What’s a common fixative for light microscopy?

A

Formalin

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11
Q

What’s a common fixative for electron microscopy?

A

Glutaraldehyde

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12
Q

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

A

Dehydration

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13
Q

How does tissue dehydration occur?

A

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

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14
Q

What occurs during clearing?

A

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

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15
Q

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

A

Infiltration

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16
Q

After infiltration, what occurs during tissue slide preparation?

A

Embedding

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17
Q

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

A

Embedding

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18
Q

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

19
Q

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

A

Light

Electron

20
Q

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

A

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

21
Q

What’s the final step of tissue preparation?

A

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

22
Q

What’s the most common type of stain?

A

Hematoxylin and eosin

23
Q

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

A

Basophilic

24
Q

Which H&E staining component stains negative cellular components?

A

Hematoxylin

25
Cellular components with a positive charge, like proteins with amino groups, stain with eosin, making these cellular components \_\_\_\_\_\_\_\_\_\_\_\_\_\_
Acidophilic
26
Hematoxylin binds ___ charges; eosin binds ___ charges Hematoxylin stains \_\_\_\_\_; eosin stains \_\_\_\_\_
Negative; positive Purple; pink
27
Which component of H&E staining serves as the counterstain?
Eosin
28
Why are counterstains useful?
Because staining procedures often label only specific structures, rendering parts of the cell invisible
29
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ staining contains three colored components to allow for greater distinction among extracellular tissue components
Masson trichrome
30
In Masson Trichrome staining, what types of cellular components are stained?
Extracellular matrix
31
In Masson trichrome staining, collagen-rich ECM stains \_\_\_\_\_, cytoplasm stains \_\_\_\_\_, and nuceli stain \_\_\_\_\_\_
Blue Pink Red/purple
32
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ stains negatively charged, sulfate-containing glycans, usually mucins or glycosaminoglycans
Alcian blue
33
\_\_\_\_\_\_\_\_\_\_\_\_\_ stains neutral glycans
Peridic acid Schiff
34
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ uses solutions of silver salts to visualize ECM fibers and nervous tissue elements
Metal impregnation
35
What type of stain is shown?
Masson trichrome
36
What type of stain is shown?
Alcian blue
37
What type of stain is shown?
Metal impregnation
38
DAPI stains __________________ the color \_\_\_\_\_\_\_\_
Nucleic acids Blue
39
In _______________ sections, specimens are cut along the direction of the organ
Longitudinal
40
In _____________ sections, specimens are cut perpendicular to the length of the organ
Cross/transverse
41
In _________________ sections, specimens are cut at an angle between cross and longitudinal sections
42
Why are sections often examined in parallel (serial sections)?
Because sections are limited to two-dimensionality, representing only a part of a larger three-dimensional structure
43
Distortion in preparatory steps may result in structural abnormalities called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, structures seen microscopically that may differ from structures present when tissue was alive
Artefacts
44
What are five problems that can result during tissue preparation and in turn distort slide interpretation?
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)