Histology Flashcards

1
Q

For Skin (structure), give the Type of Structure and Type of Basic Tissue.

A

Type of structure = Organ
Type of basic tissue = Epithelial and Connective Tissues

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2
Q

For Fascia, Tendons, Aponeurosis, Muscle, Bone (structure), give the Type of Structure and Type of Basic Tissue.

A

Fascia = Organ/Tissue - Connective Tissue
Tendon = Organ/Tissue - CT
Aponeurosis = Organ/Tissue CT
Muscle = Organ/Tissue - Muscular Tissue
Bone = Organ/Tissue - Variety of CT

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3
Q

For Nerves (structure), give the Type of Structure and Type of Basic Tissue.

A

Type of Structrue = Tissue/Organ/System
Type of basic Tissue = Nervous Tissue

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3
Q

For Blood Vessels (structure), give the Type of Structure and Type of Basic Tissue.

A

Type of Structure = Organ/Tissues
Type of Basic Tissue = Epithelial, CT, Muscular

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4
Q

What is the equivalence between nm and Angstrom units?

A

1nm = 10 A

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5
Q

What is the average thickness of a section?
What is the average diameter of a cell?
What is the average diameter of a lysosome?
What is the average thickness of plasma membrane?

A

Section = 5um
Diameter of cell = 10um
Diameter of a lysosome = 200 nm
Thickness of PM = 75A (7.5 nm)

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6
Q

For a light microscope, what are the steps required for preparation of a tissue for microscopic examination?

A
  1. Chemical fixation (formalin)
  2. Dehydration (ethanol because Xylene and water don’t mix and Xylene is needed to allow proper infiltration of paraffin)
  3. Clearing (Xylene)
  4. Infiltration (Xylene/paraffin)
  5. Embedding (paraffin)
  6. Sectioning (microtome)
  7. Mounting (glass slide)
  8. Removal of paraffin (Xylene)
  9. Rehydration (100% ethanol → 100% H2O by steps)
  10. Staining (H&E) and/or histochemical reaction)
  11. Light microscopy

*Paraffin = Wax

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7
Q

For electron microscopy, what are the steps required for preparation of a tissue for microscopic examination?

A
  1. Chemical fixation (gluteraldehyde and osmium tetroxide)
  2. Dehydration (ethanol)
  3. Clearing (propylene glycol because it dissolves plastic)
  4. Infiltration (propylene glycol/plastic)
  5. Embedding (plastic)
  6. Sectioning (ultramicrotome)
  7. Mounting (copper grid)
  8. Staining (lead citrate and/or histochemical reaction)
  9. Transmission with EM
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8
Q

For a light microscope, what are the steps required for preparation of a tissue for microscopic examination when freezing the tissue instead of doing chemical fixation?

A
  1. Freezing
  2. Sectioning (cryostat)
    From there, same steps:
  3. Mounting (glass slide)
  4. Removal of paraffin
  5. Rehydration
  6. Staining (H&E)
  7. Light microscope
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9
Q

What does the dehydration step of tissue preparation involve?

A

Start with tissue in 100% H2O solution and step-by-step go to a 100% ethanol solution
1. 50% EtOH/50% H2O
2. 60% EtOH/40% H2O
3. 70% EtOH/30% H2O

*Do opposit for rehydration

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10
Q

What are the 2 main methods of chemical fixation?

A

*Fixation stops any biological process, freezes the organ in time
1. Perfusion = injecting a fix in the artery/circulation of the specimen freezing it inside-out
- Best to preserve resolution (faster)
- Used for EM or LM

  1. Immersion = anesthetize the specimen, remove the organ and immerse it into fix solution, fixing it outside-in
    - for light microscope only
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11
Q

What solutions where/are used for Light miscroscopy fixation?

A

Before:
- Formalin (modifies nucleic acids)
- Mercuric Chloride (toxic)
- Pitric Acid (explosive)

Now:
Boin’s Fluid = Acetic Acid, Pitric Acid, Formalin (formaldehyde), Water

*For perfusion or immersion

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12
Q

What solutions are used for electron miscroscopy fixation?

A

Glutaaldehyde (2.5% - 5%)

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13
Q

What substances are used as paraffin solvent and epoxy solvents in tissue preparation for microscopy?

A

Paraffin solvent = Xylene (LM)
Epoxy (plastic) Solvent = propylene glycol (EM)

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14
Q

What are the most comon dyes in LM speciment preparation?

A

H&E:
1. Hematoxylin = basic dye
2. Eosin = acidic dye

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15
Q

What structures do Hematoxylin and Eosin stain?

A

Hematoxylin = basic dye → stains basophilic structures with blue-purple hue
- stains cell nucleus and other acidic structure

Eosin = acidic dye → stains eosinophilic structure bright pink
- Stains cytoplasm and collagen

16
Q

What are basophilic and eosinophilic structures?

A

Basophilic structures → usually the ones containing nucleic acids, ex: ribosomes, chromatin-rich cell nucleus, RNA-rich cytoplasmic regions

Eosinophilic structures → generally composed of intracellular or extracellular proteins
- Most of cytoplasm is eosinophilic

*Structures do not have to be acidic or basic, terminology is based on affinity to the dye

17
Q

What is the end-point of a LM vs an EM?

A

LM = Eye
EM = Photographic plate/phosphorescent screen

18
Q

In the EM, what is responsible for generating electrons?

A

Cathode generate e- which then travel in a high vacuum

19
Q

What are electron dense and electron lucent structures?

A

Electron lucent structure = no e- because they are reflected when hitting lead citrate (more tissue)

Electron dense structure = more electrons on the screen as then pass direclty through the plastic

*Citrate binds to tissue

20
Q

What are the wavelengths of light and of electrons? What does it mean for microscopy definition?

A

wv length of Light = 550nm, therefore d=200nm
wv length of e- = 0.02nm, therefore d=1nm

Light microscopy = 1000X magnitude
EM = 1600,000X magnitude (1.6 million with camera zoom)