MTAP (Microtomy- Flotation) Flashcards
The process of cutting very thin tissue sections using a microtome
Microtomy
5 Basic Types of Microtomes
- Rocking Microtome (Cambridge)
- Rotary Microtome (Minot Rotary)
- Sliding Microtome (obsolete type)
- Base Sledge Microtome (type of sliding microtome) - Freezing Microtome
- Vibrating Microtome
Who invented rocking microtome?
Paldwell Trefall
Oldest in design, cheap, simple, and extremely reliable. Requires very minimal maintenance
Rocking Microtome
Mechanism of action: Knife is fixed, while the tissue block moves. Tissue moves in an arc to strike the knife, between strokes, the block is moved towards the knife by a ratchet-operated micrometer thread
Steady backward and forward movement creates ribbons of good sections
Rocking Microtome
Blade moves, not the tissue, that is why its dangerous. It is also very heavy
Rocking Microtome
Invented by Professor Minot
Rotary Microtome
Designed for cutting large tissue blocks (e.g., whole brains)
Base Sledge Microtome
Rotary Microtome is also called?
Minot Rotary
Mechanism of action: Knife is horizontal and fixed. Tissue block slides backward and forward on a steel carriage
Base Sledge Microtome
Most commonly used microtome for paraffin-embedded tissues
Rotary Microtome
Mechanism of Action: Handwheel rotates 360°, specimen moves vertically past the knife. Micrometer screw advances the tissue block for precise, flat sections
Rotary Microtome
Designed for celloidin-embedded tissue blocks
and can also be used for paraffin-embedded sections
Sliding Microtome
Commonly used in neuropathology & ophthalmic pathology
Base Sledge Microtome
Advantages of Base Sledge Microtome
➔ Heavy and stable → No vibration
➔ Large wedge-shaped knife (24 cm) → Less vibration
➔ Adjustable knife-holding clamps allow angle adjustments
Mechanism of action: Knife/blade is stationary. Specimen slides under the knife during sectioning
Sliding Microtome
Disadvantages of Sliding Microtome
Very large consumes the entire bench table
This microtome is Obsolete
Sliding Microtome
Best for cutting frozen sections
Freezing microtome
Machine is clamped to the edge of a bench and connected to a CO₂ cylinder. Equipped with a knife freezing attachment
Freezing microtome
In a freezing microtome, this is used to freeze tissue
CO₂ gas
Mechanism of action: CO₂ gas is used to freeze tissue. Knife edge is cooled by CO₂ to prevent thawing. Sections transferred directly from knife to slides
Freezing microtome
Freezing Microtome – Section Thickness Gauge
Graduated in 5 µm units instead of 1 µm
Used for cutting unfixed, unprocessed, or unfrozen tissue
Vibrating Microtome
Commonly used in enzyme histochemistry & ultrastructural histochemistry
Vibrating Microtome
Mechanism of action: Tissue is immersed in water, saline, or fixative. Cut using a vibrating razor blade. Very slow cutting speed to prevent tissue disintegration
Vibrating microtome
Designed for specific types of microtomes and is used based on tissue hardness & embedding medium
Microtome Knives
Microtome knife material used for paraffin wax-embedded tissue
Steel
Microtome knife material used for resin-embedded tissue
Glass
Identify:
➔ Usually 25 mm length
➔ Flat on one side, concave on the other
Wedge knife
Identify:
➔ Usually 100 mm length
➔ Both sides straight
➔ Best for frozen sections & hard specimens (used with base sledge or sliding microtome)
Plano-Concave Knife
Identify:
➔ usually 120 mm length
➔ Both sides concave
➔ Recommended for paraffin-embedded tissue using a rotary microtome
Biconcave knife
Identify:
➔ Used for specialized applications
Tool Edge (D-Profile) Knife
Used for routine microtomy & cryotomy
Disposable blades
Used for sharp cutting edge for flawless 2-4 µm sections
Disposable blades
Disposable Blade Holders are integrated into the ____ or attached via an ______
microtome; adapter
Section Thickness for Lymph Nodes
0.5 – 2 mm
Used in electron microscopy and for plastic resin-embedded blocks
Glass & Diamond Knives
Angle between block surface & lower bevel of the knife
Clearance Angle
Angle between upper bevel & a line perpendicular to the block surface
Rake Angle
Removes irregularities from knife edges and uses abrasive stones
Honing
List the honing stones:
- Belgian black vein
- Arkansas stone
- Aloxite
- Carborundum-composites; used in households
This is used for hand sharpening, cheap & easily available, roughened surface allows abrasive particles to adhere, and easily cleaned
Glass Plates for Knife Sharpening
Automatic knife sharpening machines. Expensive, superior properties
Copper and bronze plates
Process of polishing an already fairly sharp edge.
Polishing (STROPPING)
Types of Strop
Flexible (hanging) or Rigid
Best strops are made from?
hide from the rump of the horse marked ‘shell horse’
Back of the strop is made of canvas and is intended to support the leather during stropping.
Flexible type
In a flexible type, strops should be kept soft by applying a small quantity of __________ into the back of the leather
vegetable oil
Thermostatically controlled water baths for floating out tissue ribbons after sectioning. And used to remove the creases and flatten the sections.
Floatation (water bath)
Temperature of water in the bath should be _______ below the melting point of paraffin employed.
10 degrees Celsius
In floatation, ___________ may be used to prevent water bubbles from being trapped under the sections.
distilled water
This is added to the water in the water bath to reduce the surface tension and to flatten out the section with ease
Alcohol or a small drop of detergent
True or False: the temperature of the water bath should be greater than melting point of paraffin wax
FALSE. It should NOT be greater than melting point of paraffin wax
This should be lubricated with soapy water or light oil during use
Honing using slabs of stone
