02 Sectioning Flashcards
sectioning instrument that allows for the cutting of extremely thin slices of material called section
microtome
thickness of sections
4-15 um
unit for measurement for the thickness of sections
micron
a process where wax is removed with a sharp knife until about 2 mm remains on all sides of the tissues
block trimming
action of sharpening a knife by grinding cutting edge, either on a stone or with an abrasive compound
honing
a process of polishing the cutting edge of the knife on leather or canvas done after honing
stropping
the angle formed between the cutting edge of the microtome knife
bevel angle (27-32 degrees)
the angle formed between the surface of the block and the cutting facet of the knife
clearance angle (5-10 degrees)
the straight line formed by intersection of 2 planes, the cutting facets
cutting edge
radius of curvature of the cutting edge
0.1 to 0.35 um
length of cutting facets
0.1 to 0.6 mm
angle between the sides of the knives
wedge angle (15 degrees)
angle between upper surface of the cutting facet and the surface of the block
rake angle
the ___ (smaller/bigger) the bevel angle, the sharper the knife
smaller
ensures that only the cutting edge of the knife touches the specimen block
clearance angle
too much clearance causes the knife to ___
chatter
knife design and cut type:
extremely sharp, but are also very delicate and are therefore only used with very soft samples
planar concave
knife design and cut type:
more stable and find use in moderately hard materials, such as in epoxy or cryogenic sample cutting
wedge profile knives
knife design and cut type:
with its blunt edge, raises the stability of the knife, whilst requiring significantly more force to achieve the cut
chisel profile
knife design and cut type:
used on sliding, rotary, and rocking microtomes
plano-concave knife
knife design and cut type:
used for rocking microtome and sledge microtome
biconcave knife
length of biconcave knife
100-250 mm
knife design and cut type:
less rigid and prone to vibration; rarely used in histopathology
biconcave knife
size of wedge knife
100 - 350 mm
knife design and cut type:
most commonly utilized steel knife for routine histopathology; standard knife profile
wedge knife
T/F: wedge knife profile cannot be ground as sharp as biconcave and planar-concave knives
T
this is caused by defect in the blade edge, calcium, bone or hard material in the specimen
vertical scratches
this occurs when the block is faced too aggressively
holes in the section
this happens when the specimen is excessively dehydrated or improperly processed
holes in the section
tissue adhesive:
background staining may be detected due to its uptake of dyes
albumin
added to albumin to increase viscosity and prevent complete drying
glycerol
components for Meyer’s egg albumin
equal parts glycerin, distilled water, and egg white
added to albumin to inhibit growth of molds
thymol crystal
tissue adhesive:
provides firmer attachment than albumin
Gelatin USP
tissue adhesive:
greater adhesion than gelatin but stains with many dyes
starch
tissue adhesive:
not staining to any appreciable extent with commonly used in stains of histochemical reagents
cellulose
tissue adhesive:
used as a general-purpose section adhesive
poly-l-lysine
tissue adhesive:
no production of background staining
poly-l-lysine
tissue adhesive:
used to improve section adhesion, particularly in immunocytochemistry
poly-l-lysine
tissue adhesive:
greatest adhesion; commonly used as an embedding medium for electron microscopy
resins (araldite)
tissue adhesive:
a new advancement in section adhesion; can withstand repeated washings with a variety of inorganic solvents
3-Aminopropryltriethoxysilane (APES)
tissue adhesive:
used as an adhesive for enhancing chromosome spreading on glass slides and for in situ hybridization of frozen sections
3-Aminopropryltriethoxysilane (APES)
type of microtome:
consists of a heavy base and two arms; the lower arm rests on a column and supports the upper, both being pivoted on knife edges which acts as fulcrum
cambridge rocking microtome
type of microtome:
the section cutting is affected by the vertical rise and fall of the object against a fixed knife edge
rotary microtome
type of microtome:
most widely used, also called Minot microtome
rotary microtome
type of microtome:
the knife is stationary and the block is moved up and down in a vertical plane by the rotary action of the hand wheel
rotary microtome
type of microtome:
for extremely hard specimens
sliding or base-sledge microtome
type of microtome:
has carbon dioxide type or cryostat
freezing microtome
type of microtome:
has a knife-horizontal motion
sliding or base-sledge microtome
temperature for initial deparaffinization
60-65C
