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Biology Practical 1 > Micro-techniques > Flashcards

Micro-techniques Flashcards

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1
Q

What are the requirements to study tissues under the microscope?

A
  1. The tissue sample must be stained
  2. The tissue sample must be cut very thinly
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2
Q

What are the methods of tissue preparation for a light microscope?

A
  1. Paraffin technique
  2. Freezing
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3
Q

What is the method of tissue preparation for an electron microscope?

A
  1. Electron microscopic preparation
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4
Q

What is the aim of tissue processing (LM)?

A

To put tissue in a substance (wax) that allows it to be thinly sliced in a correct arrangement.

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5
Q

What are the types of fixatives we can use for paraffin blocks?

A
  1. Acetic acid
  2. Formaldehyde
  3. Ethanol
  4. Glutaraldehyde
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6
Q

What is the main fixative commonly used in the paraffin technique?

A

Formaldehyde

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7
Q

Aim of fixation

A
  1. To prevent autolysis and bacterial attack
  2. To fix tissues os they will change shape and volume during processing
  3. To prepare tissue for staining
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8
Q

Aim of dehydration

A

To remove water from tissues to allow tissues to be placed in the paraffin wax

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9
Q

What is the common dehydrating agent and why?

A

Alcohol, because it is a hydrophilic substance (it attracts water)

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10
Q

How are specimens dehydrated?

A

in a graded ethanol series from water through
10%
20%
50%
95%
100%
of ethanol to prevent shrinking

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11
Q

Aim of clearing?

A

removing alcohols and permitting tissue infiltration with paraffin wax

Extra info:
Clearing is performed after dehydration to replace the ethanol content of the tissue with xylene. This process makes the tissue transparent, which renders the specimen suitable for microscopy.

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12
Q

Clearing

A

a process of replacing the dehydrator with a substance that is miscible with embedding medium or paraffin wax.

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13
Q

Some clearing agents?

A
  1. Xylene
  2. Chloroform
  3. Benzene
  4. Petrol
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14
Q

Aim of embedding?

A

Tissues are surrounded by a paraffin wax which when solid will provide external support for the tissue to be cut.

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15
Q

What is the most important step in embedding?

A

Correct orientation of tissue in mould

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16
Q

How are paraffin blocks cut?

A

by a microtome

17
Q

Microtome

A

machine that cuts paraffin blocks using a metal knife, 6u (micrometer) in thickness

18
Q

Mounting

A

sections spread on hot plate, mounted on glass slides

19
Q

Staining

A

Special dyes are used to stain histological sections (2D slices of tissue from a 3D piece of tissue) and make them ready for microscope examination

20
Q

what are the two commonly used dyes for paraffin wax?

A
  1. Haematoxylin (Hx)
  2. Eosin (E)
21
Q

Reactions of stains

A
  1. Acidic - Eosin stain
  2. Basic - Haematoxylin stain
  3. Neutral - Leishman stain
22
Q

Physical stain

A

No reaction in fatty tissues; the stain is SUDAN III

23
Q

Vital stain

A

The staining of living tissues inside the body

24
Q

What is the vital stain used for?

A

To stain phagocytic (immune cells) as TRYPAN BLUE

25
Q

Metachromatic stain

A

Staining tissues a colour different from the original stain. (ex: red stain shows blue when staining a tissue)

-Toluidine blue staining of mast cells

26
Q

Mast cells

A
27
Q

Phagocytic cells

A

-Type of white blood cell

-Uses phagocytosis to engulf:
bacteria
foreign particles
Dying cells

Usage: To protect the body

28
Q

Histo-chemical stain

A

Staining tissue to identify components of the cell as glycogen and protein

29
Q

Freezing technique

A

-Water-rich tissues are hardened by freezing and then cut
-sections are examined by (LM)
-Much faster than paraffin and is used in operations to acquire a quick diagnosis

30
Q

Which technique is faster paraffin or cryosection?

A

cryosection

31
Q

what is a synonym for freezing technique?

A

cryosection

32
Q

What is an electron microscope used for?

A

To show ultrastructure (deep magnification of the structure of cells)

33
Q

Fixation (EM)

A

uses glutaraldehyde and osmium tetraoxide

34
Q

Embedding (EM)

A

Tissues are inserted in Epon (type of resin) in gelatin capsule

35
Q

Cutting (EM)

A

-capsules are cut by ultra-microtome
-using glass/diamond knife
-section measurement 50-100nm

36
Q

Mounting

A

sections mounted on metal grids

37
Q

Staining

A

by heavy metals (lead nitrate and uranyl acetate)

38
Q

Blasais

A

Hajkskd

Biology Practical 1 (2 decks)

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