Microtomy

Question 1

The angle formed between the block and the cutting facet of a knife is known as the:

Answer 1

clearance angle

Question 2

which of the following embedding procedures involves first infiltrating the tissue with one medium and then embedding it with another?

a. double
b. resin
c. routine
d. vacuum

Answer 2

a. double embedding

for friable tissue or multiple fragments: infiltrate in gelatin and embedding in agar

Question 3

When frozen sections stick to a cryostat anti-roll plate, the plate is:

Answer 3

too warm

Question 4

To remove grit and dirt before embedding, paraffin may have to be:

a. filtered
b. heated
c. solidified
d. washed

Answer 4

a. filtered

Question 5

it is important that the faced of a cryostat knife be small to prevent:
a. loose metal shavings from attaching to the sections
b. problems with the anti-roll plate
c. the section from curling as it is cut
d/ the venetian blind effect

Answer 5

b. problems with the anti-roll plate

Question 6

Microscopic examination of an H&E section reveals marked background stainings. This is caused by:

a. albumin spread on the slide by a finger
b. excess section adhesive on the slide
c. sections being taken immediately after rough facing the block
d. the flotation bath not being cleaned between blocks

Answer 6

b. excess section adhesive on the slide

Question 7

when frozen sections appear above the anti-roll plate of a cryostat, the plate is:

Answer 7

too far below the knife edge

Question 8

during sectioning of a block of uterine tissue, alternate thick and thin zones are observed, this is caused by:

a. improper embedding
b. inadequate processing
c. vibration of the knife
d. non-parallel block edges

Answer 8

c. vibration of the knife

Question 9

which tissue should be sectioned at 3um?

a. brain
b. breast
c. liver
d. lymph node

Answer 9

d. lymph node

Question 10

sections are being lifted from the knife on the upstroke. This is probably because the:

a. knife is too sharp
b. knife tilt is incorrect
c. paraffin is too cold
d. specimen is too hard

Answer 10

b. knife tilt is incorrect

Question 11

when frozen sections partially jam and partially slide under the anti-roll plate, the plate is:

Answer 11

Not parallel to the knife edge

Question 12

which if the following groups of plates may be used to support abrasive powders and lubricants for sharpening knives?

a. copper, glass, iron
b. aluminum, copper, glass
c. copper, iron, aluminum
d. glass, aliminum , iron

Answer 12

b. aluminum, copper, glass

never iron! it rusts too quickly

Question 13

which of the following could be substituted for gelatin as an additive to the flotation bath?

a. aminoalkylsilane b. chromium potassium sulfate
c. poly L-Lysine
d. agar

Answer 13

d. agar

for flotation bath: agan, gelatin and Elme’s glue

Question 14

A finger nail has been fixed in formalin, processed and embedded in paraffin. The tissue is very hard and sections are difficult to obtain. Sectioning quality will be improved and tissue component will be best preserved and demonstrated by gently facing the block and: a. soaking in water

b. warming the block slightly
c. soaking in a solution that softens keratin
d. treating with decalcifying fluid

Answer 14

c. soaking in a solution that softens keratin

Question 15

The solution used in the knife tough when sectioning epoxy resins is usually:

Answer 15

water

Question 16

a section of skeletal muscle has been frozen in isopentane and liquid nitrogen, but numerous holes are seen in H&E sections .this problem is casued by:

a. non-isometric fixed muscle tissue
b. sectioning too soon after freezing
c. leaving in isopepentane too long
d. isopentane that is not cold enough

Answer 16

d. isopentane that is not cold enough

must reach -150C to preven ice crystal artifacts= holes

Question 17

“thick” sections for EM, or sections to be viewed with the light microscopy, are cut at:

Answer 17

0.5 to 1.0 um

Question 18

Tissued to be sectioned with a cryostat may be somewhat protected from ice crystals artifacts by using:

Answer 18

infiltrating with 30% sucrose before freezing (also helps preserve membranes)

Question 19

Glass knives suitable for cutting plastic blocks of medium hardness will have a cutting edge angle of:

Answer 19

45 degrees

Question 20

During the sectioning of the plastic blocks with an ultramicrotome, no sections are being cut. The problem is most likely caused by:

a. dirt
b. dull knife
c. a loose knife
d. an incorrect water level

Answer 20

b. dull knife

Question 21

Glass knives are being made for cutting ultra-thin sections. The time for obtaining good sections requires that these knives should be used within the same___ as being made:

a. hour
b. day
c. week
d. month

Answer 21

b. day

note: ultra-thin are usually cut on diamong knives at 90nm

Question 22

diamond knives are used in ultramicrotomy because steel knives :

a. connot withstand the electron beam
b. leave steel shaving in ultrea-thin section
c. react with the chemicals in the resin blocks
d. are quickly dulled

Answer 22

d. are quickly dulled

Question 23

grids used to support epoxy-embedded sections for Em are usually made from:

a. copper
b. iron
c. lead
d. zinc

Answer 23

a. copper

Question 24

A microscopy section of liver tissue shows numerous irregular holes through the tissue. This is most likely because:

a. the holes are portal triads
b. liver is difficult to cut
c. fixation has been prolonged
d. sectioning technique was poor

Answer 24

d. sectioning technique was poor

Question 25

Successive cryostat sections catch on one area in the middle of the anit-roll plate. The most likely cause is that the anti-roll plate is:

a. warmer than the knife
b. colder than the knife
c. improperly adjusted
d. damaged

Answer 25

d. damaged

bc succesful sections where obtained

Question 26

Mayer egg albumin is observed to be contaminated with bacterial growth. the most probable explanation is that during preparation:

a. the reagent was inadequately heated
b. a non-sterile storage contained was
c. thymol was omitted
d. the eggs used in preparation were contaminated

Answer 26

c. thymol was omitted

thymol prevents microscopic growth in solutions

Question 27

A ribbon of paraffin embedded brain tissue is floated on the water bath. small holes are noted on the first section that decrease in size in subsequent sections. The most appropriate action is to:

a. melt the block and re-embed the tissue
b. resharpen the knife
c. decrease the water bath temperature
d. cut and discard ribbons until the holes disappear

Answer 27

d. cut and discard ribbons until the holes disappear

this can is probably a paraffin bubble

Question 28

Breathing on blocks during sectioning should be kept to a minimum when using:

a. celloidin
b. epon
c. paraffin wax
d. polyster wax

Answer 28

d. polyster wax

Question 29

During fozen sectioning, the sections roll up and jam in front of the anti-roll plate. This is most likely due to the:

a. anti-roll plate being too low on the knife edge
b. anti-roll plate not being parallel to the edge of the knife
c. cryostat temperature being too low
d. space between the knife and the antiroll plate being too great

Answer 29

a. anti-roll plate being too low on the knife edge

Question 30

which groups of abrasive compounds is used for microtome knife sharpening?

Answer 30

carborundum, diamond and jewel’s rouge

Question 31

what is the main purpose of the flotation bath for paraffin ribbons?

Answer 31

warm water to relax the tissue and remove wrinkles/folds before placing it on a slide