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FOM - WLB > Week 5 Downing - Histology Methods, Epithelium, CT Proper > Flashcards

Week 5 Downing - Histology Methods, Epithelium, CT Proper Flashcards

1
Q

Light Microscope

A

A.K.A. Bright Field

-routine laboratory microscope used for studying tissue sections

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2
Q

Transmission Electron Microscope (TEM)

A

Used to study cytology or internal structures of cells

(study of electron micrographs)

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3
Q

Scanning Electron Microscope (SEM)

A

Used to study the surface features of cells and tissues

(obtain a 3-dimensional picture of the tissue)

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4
Q

Polarizing Microscope

A

Permits one to determine whether biological materials have different refractive indices along different optical axes.

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5
Q

Phase Microscope

A

Used to study living tissue.

(works on a principal of different refractive indices of cellular and sub-cellular components)

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6
Q

Interference Microscope

A

A modification of the phase microscope used for the study of living tissue.

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7
Q

Fluorescence Microscope

A

Used to examine the presence of fluorescent material in tissue sections.

(Uses UV light as the light source)

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8
Q

Confocal Scanning Microscope

A

Used to optically section a cell and with the appropriate computer equipment can reconstruct a

3-D image of the cell.

(uses a layer energy beam)

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9
Q

What are the 6 steps in preparing tissues for bright field microscopy?

A
  1. Fixation (stabilize tissue structure)
  2. Dehydration (remove water, make miscible)
  3. Clearing (replace alcohol with agent miscible to paraffin)
  4. Infiltration & Embedding (replace clearing agent with embedding material)
  5. Sectioning (cut tissue into thin sections)
  6. Staining (add color)
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10
Q

How can frozen histological sections be useful?

A
  • pathology examination
  • localization of enzymes
  • analyze tissue sample
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11
Q

What are 6 common artifact in tissue slides?

A
  1. Post-mortem degeneration
  2. Shrinkage
  3. Precipitates (bad formalin)
  4. Wrinkles & Folds
  5. Nick in the microtome knife (results in tearing or scraping of tissue when cutting)
  6. Mishandling (pinching of tissue)
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12
Q

What is an acidic dye?

A

Capable of forming a salt linkage with a positively charged tissue group.

(dye molecule is negatively charged - anionic)

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13
Q

What is a basic dye?

A

A positively charged (cationic) and hence forms a salt with a negatively charged tissue group.

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14
Q

What is an H stain?

A

Hematoxylin (blue → purple)

basic stain

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15
Q

What is an H stain used for?

A

To stain basophilic substances.

  • DNA
    • chroms
    • heterochromatin
  • RNA
    • nucleolus
    • cytoplasmic ribosomes
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16
Q

What are basophilic tissues?

A

Structures in the cell or tissue that love basic stains.

(e.g. nucleus)

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17
Q

What is an E stain?

A

Eosin (red → pink)

acid stain

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18
Q

What is an E stain used for?

A

Acidophilic substances (eosinophilic substances)

  • Proteins
  • Cations associated with side chains
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19
Q

What are acidophilic tissues?

A

Structures in the cell or tissue that love acid stains.

(a.k.a. eosinophilic substances)

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20
Q

When is Trichrome stain used?

A

Stain for connective tissue (collagen) rather than cells.

(e.g. Masson’s, Mallory’s)

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21
Q

When is Elastic stain used?

A

When staining for elastic fibers or elastic tissue in connective tissue.

(e.g. aldehyde fuchsin, orcein, resorcin-fuchsin)

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22
Q

When are Silver stains used?

A

When staining for reticular fibers in connective tissue.

Also for staining cells of the CNS.

(connective tissue fibers love silver and stain black - argyrophilic)

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23
Q

When are Fat stains used?

A

Oil red O - stains fats red

Sudan black - stains fats black

*soluble in both alcohol & fats

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24
Q

What is used to stain nucleic acid (DNA & RNA)?

A

Feulgen staining reaction for DNA

25
Q

What is used for staining carbohydrates?

A

Periodic acid-Schiff reaction (PAS)

26
Q

What does Immunocytochemistry allow?

A

Permits the cellular or intracellular localization of specific proteins.

27
Q

Why are red blood cells useful in determining approximate magnifications of tissue images?

A

They are about 7um (micrometer) thick.

Can be used as a reference size.

28
Q

What is the basic mechanism of the Periodic acid-Schiff reaction (PAS)?

A
  • Oxidizes diols in sugars → creates two aldehydes
    • aldehydes react with Schiff’s agent

​

*Used to detect carbs (polysaccharides, glycogen)

29
Q

What is the basic mechanism of the Feulgen staining reaction?

A
  • HCl removes purine bases from DNA
    • unmasks free aldehyde groups
    • free aldehyde groups react with Schiff’s reagent
      • purple stained DNA!!!

(does not work on RNA)

30
Q

What are the four major types of tissues in the body?

A
  1. Epithelium tissue
  2. Connective tissue
  3. Nervous tissue
  4. Muscle tissue
31
Q

What are the four general characteristics of Epithelia?

A
  1. Sheets or layers of cells in close apposition
  2. Cover surfaces/line cavities
  3. Very little intercellular material (epithelium = highly cellular tissue)
  4. Always in contact with a basal lamina
32
Q

What germ layers give rise to Epithelia?

A

ALL THREE!

(ectodoerm, mesoderm, & endoderm)

33
Q

What are tight junctions?

A
  • Zonula occludens
    • apical domain
    • cadherin
    • freeze fracture technique: pattern of ridges
34
Q

What are integrins? What is one example?

A

Mediate cell-extracellular matrix interactions.

ex. Hemidesmosomes

35
Q

What are cadherins? What are some examples?

A

Mediate cell-cell interaction.

ex. Zonula occludens, Zonula adherens, Macula adherens

36
Q

What are belt desmosomes?

A
  • Zonula adherens
    • belt of adhesion
    • cadherin
    • not as close as tight junctions
    • cytoplasmic domains interact with actin microfilaments via linker proteins
37
Q

What are spot desmosomes?

A
  • Macula adherens (desmosomes)
    • form spot-like “welds” between adjacent epithelial cells
    • cadherin
    • transmembrane proteins
      • desmogleins & desmocollins
    • desmoplakins
      • dense plaque
      • interacts with intermediat filaments
38
Q

What are hemidesmosomes?

A
  • looks like half of a desmosome
  • forms between cell membrane of a basal epithelial cell and the adjacent basal lamina
  • integrin
  • cytoplasmic domains interact with intermediate filaments via linker proteins
  • extracellular domains interact with laminin found in the basal lamina
39
Q

What are gap junctions?

A
  • Nexus
    • 6 transmembrane protein subunits form connexin
    • line up with opposite and identical structure in an adjacent cell
      • create channel pore that connects the cytoplasm of the two adjacent cells
40
Q

What are the two components of the basement membrane?

A
  • Basal lamina
    • lamina lucida
    • lamina densa
    • lamina reticularis
  • Hemidesmosomes
41
Q

What does the first part of the basal lamina, the lamina lucida, do?

A
  • electron lucent portion of basement membrane
  • rich in glycoproteins, laminin, and entactin
  • binds to integrins
42
Q

What does the second part of the basal lamina, the lamina densa, do?

A
  • dense meshwork of type IV collagen
    • sandwiched by the proteoglycan perlacan containing heparan sulfate side chains
  • tightly anchored to reticular lamina
    • by fibronectin
43
Q

What does the third part of the basal lamina, the lamina reticularis, do?

A
  • forms interface between the basal lamina and underlying connective tissue
44
Q

What is the structure and function of microvilli?

A
  • microscopic projections above free surface
  • covered with cell membrane
  • core of microfilaments
  • form “brush border”
  • increase surface area of cell
45
Q

What is the structure and function of stereocilia?

A
  • unusually long microvilli appearing
  • apical ends twist together
  • non-motile
  • increase absorptive surface of cells
46
Q

What is the structure and function of cilia?

A
  • motile processes that extend from the apical surface of the cell
  • shaft covered with plasma membrane
  • arise from basal bodies
  • axoneme: internal/core structure
    • two single, central microtubules
    • nine peripheral pares of fused double microtubules
      • A-tubule (complete) + B-tubule (incomplete)
      • doublets connected by nexin link
      • dynein walks toward minus (-) end of doublet
47
Q

What is the structure and function of flagella?

A
  • same axial structure as cilia
  • much longer than cilia
  • beat is more random, whip-like motion
48
Q

Epithelioid

A

term for an epithelium-like appearance of non-epithelial cells

49
Q

Metaplasia

A

An abnormal change from one distinctive kind of cell to another at a definite site after development is over.

50
Q

Neoplasia

A

An abnormal change from on distinctive kind of cell to a tumor cell.

ex. carcinoma: a malignant neoplasm of epithelial origin

  • benign
  • metastatic
51
Q

Hyperplasia

A

An increase in the number of cells in a tissue or organ, excluding tumor formation.

Increases the bulk of the part or organ.

52
Q

Hypertrophy

A

Overgrowth or general increase in bulk of a part or organ.

53
Q

Anaplasia

A

Loss of structural differentiation.

Particularly prevalent in malignant neoplasms.

54
Q

What is the embryological origin of connective tissue?

A

Mesoderm!

55
Q

What are the physical characteristics of collagen?

A

Microfibril x3 → Fibril x3 → Fiber → Aggregate to form Bundle

  • flexible
  • non-extensible (inelastic)
  • forms gelatin when placed in boiling water
56
Q

What is the chemical composition of collagen fibers?

A
  • polymerization of tropocollagen molecules into fibrils
    • three chains of polypeptides (280nm long)
    • triple helix
57
Q

What is the chemical composition of amorphous intercellular substance (ground substance)?

A
  1. water
  2. glycosaminoglycans
  3. proteoglycans
  4. structural multi-adhesive glycoproteins (fibronectin, laminin)
58
Q

What is the function of ground substance?

A
  • efficient space filler
  • permits passages of gases, ions, and small particles
  • helps to immobilize larger objects (e.g. bacteria)
59
Q
A

FOM - WLB (20 decks)

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