SECTION-CUTTING, HONING AND STROPPING Flashcards
Three Basic Types or Shapes
- Plane-Concave Knife
- Biconcave Knife
- Plane-Wedge Knife
Trimming and section-cutting are done w/ a
microtome knife
(25 mm in length)
Plane-Concave Knife
-One side of the knife is flat while other is concave.
Plane-Concave Knife
-Less concave sides are recommended for cutting Celloidin-embedded tissue blocks on a sliding microtome
microtome
-More concave sides used to cut paraffin sections on base-sledge, rotary or rocking Microtome
Plane-Concave Knife
(usually 120 mm in length)
Biconcave Knife
-w/ both sides concave
Biconcave Knife
-recommended for cutting paraffin-embedded sections on a rotary microtome
Biconcave Knife
(usually 100 mm in length)
Plane-Wedge Knife
-both sides straight
Plane-Wedge Knife
- recommended for frozen sections or cutting extremely hard and tough specimens embedded in paraffin blocks
- using a base-sledge type or sliding microtome
Plane-Wedge Knife
-it is the angle formed between cutting edges. It usually 27o to 32o
“Bevel Angle”
the angle formed between cutting edges of a bevel angle
27o to 32o
-a good cutting edge should be made of good quality steel. Too soft cutting edges are likely to become dull easily, while too hard edges are likely to produce nicks or jagged edges and irregularities, thereby producing tears or striation on the tissue sections during cutting.
“Bevel Angle”
-a good cutting edge must be able to cut good sections from a paraffin wax block about 2-3 microns thick, without any serration noted on examination.
“Bevel Angle”
Theoretically, the perfect and optimum cutting angle is obtained when the sides of the wedge knife are inclined at an angle of about 15 degrees, causing maximum penetration of the tissues and minimizing distortion, causing maximum penetration of the tissues and minimizing distortion.
Clearing angle
-process where badly nicked knives w/ blunted ends, jagged edges must undergo sharpening in order to prevent gross irregularities and tearing of tissue sections.
Honing and Stropping
Sharpening of knife involves two stages:
- Honing
2. Stropping
-removal of gross nicks on the knife (coarse honing) to remove blemishes and grinding the cutting edge of the knife on a stone
Honing
a natural sharpening stone or hard grinding surface (carborundum) serves to remove nicks and irregularities of the knife edges
Hone
Types of Hones:
- Belgium Yellow
- Arkansas
- Fine carborundum
much coarser than the first two, used only for badly nicked knives followed by either the two
Fine carborundum
gives more polishing effect than Belgium Yellow
Arkansas
for manual sharpening when cutting edge has been rendered blunt or nicked. This type give the
best result
Belgium Yellow
Lubrication:
a. Mineral
b. Clove oil
c. Xylene
d. Liquid paraffin or soapy water
- Edge First, w/ a Heel to Toe direction
Honing
-Process whereby the “burr” formed during honing is removed and the cutting edge of the knife is polished.
Stropping
Edge last, Toe To Heel direction
Stropping
can cut 2-4 micra thick section
Disposable Blades
-suitable for use in the cryostat
Magnetic knives
-used for trimming and semi-thin sectioning of tissue blocks for electron microscopy
Glass Knives
are used to cut any type of resin block for electron microscopy-are used to cut any type of resin block for electron microscopy
Diamond Knives
is a process whereby tissues are cut into uniformly thin slices or “sections”
“Sectioning”
Three General Types of Tissue Sections
- Paraffin Sections
- Celloidin Sections
- Frozen Sections
w/c may be cut from tissues that have been fixed and frozen w/ CO2 or for fresh or fixed
tissues frozen w/ cryostat
Frozen Sections
for celloidin embedded tissues w/c are usually cut by means of the sliding microtome for celloidin embedded tissues w/c are usually cut by means of the sliding microtome
Celloidin Sections
paraffin embedded tissue blocks w/c may be cut by rocking and rotary microtome
Paraffin Sections
