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 ___________________

A

Microtome

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
Q

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

A

Acidophilic

26
Q

Hematoxylin binds ___ charges; eosin binds ___ charges

Hematoxylin stains _____; eosin stains _____

A

Negative; positive

Purple; pink

27
Q

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

A

Eosin

28
Q

Why are counterstains useful?

A

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

29
Q

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

A

Masson trichrome

30
Q

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

A

Extracellular matrix

31
Q

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

A

Blue

Pink

Red/purple

32
Q

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

A

Alcian blue

33
Q

_____________ stains neutral glycans

A

Peridic acid Schiff

34
Q

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

A

Metal impregnation

35
Q

What type of stain is shown?

A

Masson trichrome

36
Q

What type of stain is shown?

A

Alcian blue

37
Q

What type of stain is shown?

A

Metal impregnation

38
Q

DAPI stains __________________ the color ________

A

Nucleic acids

Blue

39
Q

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

A

Longitudinal

40
Q

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

A

Cross/transverse

41
Q

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

A
42
Q

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

A

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

43
Q

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

A

Artefacts

44
Q

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

A
  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)