Introduction to Histology

Question 0

Name 5 types of biopsy.

Answer 0

1. Needle
2. Endoscopic
3. Transvascular
4. Direct excision
5. Curettage

Question 1

What are the preparatory steps for microscopy?

Answer 1

1. Tissue Collection
2. Fixation (dehydration, clearing)
3. Embedding
4. Sectioning
5. Mounting/Staining
6. Viewing

Question 2

What is the goal of fixation?

Answer 2

Preserve tissue by preventing degradation. Maintains structure.

Question 3

Name 4 fixatives (2 chemicals, 2 techniques).

Answer 3

Glutaraldehyde
Formaldehyde
Dehydration
Rapid Freezing

Question 4

How do aldehydes (formaldehyde, glutaraldehyde) fix?

Answer 4

By crosslinking 3 amino groups and nitrogenous groups. Crosslinks every molecule within tissues, causing loss of biologic activity. Also prevents damage from unfriendly microbes.

Question 5

What type of sample would you use dehydration to fix? What are the steps in this fixative process?

Answer 5

Dehydration used to fix monolayers of cells, or when tissue is readily available. Use a tissue of 80% alcohol for short periods of time.

Question 6

What would you use for rapid freezing fixation?

Answer 6

Liquid isopentane at -160 degrees C.

Question 7

Name 3 ways you could embed a sample (what would you use)?

Answer 7

1. Paraffin wax
2. Acrylic resin
3. Freezing

Question 8

How thin of slices can you section parafin wax? What viewing method is parafin wax used for? What is an advantage and disadvantage?

Answer 8

1. 5-8 microns
2. Light Microscopy
3. Advantage: Good resolution of cell structure/tissues
4. Slow (24 hours)

Question 9

How thin can you section acrylic resin? What viewing method is acrylic resin used for? What are 2 disadvantages?

Answer 9

1. 60nm to 1 micron.
2. EM
3. Incompatible with most histological stains, very slow (a few days).

Question 10

How thick can you section frozen sections? What are 3 advantages of embedding by freezing?

Answer 10

12 to 20 micron sections.

1. very fast
2. can use immunological/histochemical stains
3. maintains biologic activity when warm

Question 11

Why do we stain samples?

Answer 11

Very little natural pigment. 90% water.

Question 12

What does hematoxylin stain?

Answer 12

Hematoxylin stains acidic stuff blue. Stuff includes nucleic acids (nuclei, ribosomes, cartilage matrix).

Question 13

What does eosin stain?

Answer 13

Eosin stains basic stuff pink. Stuff includes cytoplasm, collagen fibers.

Question 14

What colors are the stains of Masson’s Trichrome? What do each color stain?

Answer 14

1. Dark blue: nuclei,
2. Red: muscle, keratin, cytoplasm (red meat, red nails)
3. light blue: mucinogen, collagen (unlike eosin, which stains collagen pink).

Question 15

What does Weigart’s stain stain? What color?

Answer 15

Elastic fibers, blue.

Question 16

What does Silver stain stain? What color?

Answer 16

Neurofilaments, reticular fibers. Black.

Question 17

What does iron hematoxylin stain? What color?

Answer 17

muscle (pump iron yo)
nuclei
erythrocytes (hemoglobin has iron yo)
Black.

Question 18

What does Periodic Acid Schif stain? What color? Would it stain a Goblet cell?

Answer 18

PAS stains carbohydrate rich molecules (eg glycogen) magenta. It would stain goblet cells, which make mucinogen and contains mucopolysaccharides.

Question 19

Why would you use Wright’s stain? How does Wright’s staining differ from HE staining? What colors, and what do each color stain?

Answer 19

To differentiate blood cells. Wright uses methylene blue instead of hematoxylin.
Pink: erythrocytes, eosinophil granules.
Blue: Nuclei of wbc, cytoplasm of monocytes/lymphocytes.

Question 20

Total magnification of microscope= ____x____

Answer 20

objective lens magnification x ocular lens magnification

Question 21

How small can human eyes resolve 2 points?

Answer 21

0.1-0.2 mm.

Question 22

How small can a light microscope resolve 2 points?

Answer 22

.25 microns

Question 23

How small can TEM resolve 2 points?

Answer 23

0.2 nm. Highest resolution so far.

Question 24

How small can SEM resolve 2 points?

Answer 24

10 nm.

Question 25

What must you keep in mind when viewing a histological section in regards to shape?

Answer 25

A section is a 2D section of a 3D object. These sections could have a variety of positions,

Question 26

What can you use as a scale when viewing tissue when no scale is given? How wide is this structure?

Answer 26

Erythrocytes. 7.5 microns.

Question 27

What stain would you use to visualize goblet cells and glycocalyx?

Answer 27

Periodic Acid Schif. Goblet cells have mucopolysaccharides and glycocalyx has oligosaccharides and proteoglycans.

Question 28

What technique would you use to visualize enzyme activity?

Answer 28

Enzyme histochemistry. Cleaves artificial substrate resulting in colored deposits.

Question 29

What technique would you use to visualize macromolecules?

Answer 29

Immunocytochemistry. Using labeled Ab.

Question 30

What technique would you use to visualize incorporation of a synthetic molecule in a newly synthesized protein?

Answer 30

Autoradiography. (mouse salivary gland example). Bad flashcard.

Question 31

Green neurofilament. Red synaptic vesicles. What did they use to visualize this neuron?

Answer 31

Double Immunofluorescence.

Question 32

What would you use as a stain for TEM?

Answer 32

Heavy metals (uranyl acetate, lead citrate).

Question 33

How does SEM differ from TEM?

Answer 33

SEM scans surface structures. 10 nm resolution compared to .2 nm resolution.