1) A microtome is a tool used to cut extremely thin slices of material for microscopic examination. It was developed to allow for the precise cutting of tissue sections thin enough for light to pass through. 2) There are several types of microtomes including rotary, rocking, base sledge, freezing, vibrating, saw, sliding, cryostat, and ultramicrotome. The rotary microtome is the most common type used for routine research due to its ability to cut flat serial sections. 3) A cryostat allows cutting of unfixed fresh or frozen tissue sections and maintains the tissue at low temperatures during sectioning to preserve cellular structures, though it cannot be used for fixed

1. MICROTOME

2. Why do we preserve tissue samples ???
• For gross display in the Museum .
• For microscopic evaluation .

3. For Microscopic Study
The Major tissue component ,
• Is initially fixed using a suitable fixative .
• Undergoes adequate change in solutions , at adequate time - PROCESSING .
• Embedded in paraffin wax as BLOCKS .
• From the blocks , thin tissue sections are cut using specialized equipment
called MICROTOME .
• Stained & studied under a microscope

4. MICROTOMY
• The art of section cutting.
• This is a process of cutting thin sections of tissue embedded in
the wax block using a microtome .
MICROTOME
• Basic instrument / Mechanical device for cutting thin uniform
slices of tissue .

5. HISTORY
• In the beginning of microscopy , sections were made with Razor blades.
• This method failed due to the impossibility of light transmission through
thicker tissue .
• Only with proper clean reproducible cuts of 100 μm , light can be
transmitted , allowing precise observation of tissues to be carried out .

6. With this idea , one of the first
devices for such cuts were
designed by George Adams in the
year 1770 & was further developed
by William Cunnings .
Named as CUTTING ENGINE .
Hand operated machine
A cylinder to hold sample & a hand
crank to cut .

7. • Then the word Microtome was derived from Greek mikros, meaning
"small", & temnein, meaning "to cut" .
• It is a tool used to cut extremely thin slices of material, known as Sections.
• Important in science to cut sections for microscopical observation.
• Microtomes use steel , glass , or diamond blades depending upon the
specimen type & desired thickness of the sections to be cut .
• Sections can be made as thin as , breadth of a human hair , between
50 – 100 μm .

8. • After several modifications , today we use microtomes of
KNIFE BLOCK DESIGN.
• It has a
Changeable knife , &
Specimen holder.
• Automatic machines are also available , where the sample moves
over the knife with a precision control of tissue thickness.

9. Sectioning using Razor blades .

10. VINTAGE
MICROTOMES

11. First clinical use of microtome

12. TYPES OF MICROTOMES
Based upon the mechanism ,
• Rotary
• Rocking
• Base sledge
• Freezing
• Vibrating
• Saw
• Sliding
• Cryostat
• Ultra-Microtome

13. ROTARY MICROTOME
So called because of the Rotary action of hand wheel used for cutting
movement.
The block holder is mounted on a steel carriage, which moves in grooves ,
up & down.
Most ideal for routine & research work .
Excellent for cutting serial sections.

14. PARTS OF THE ROTARY MICROTOMES
• Block holder
• Knife clamp screw
• Knife clamps
• Block adjustment
• Thickness gauge
• Angle of tilt adjustment
• Operating handle

15. • The feed mechanism is activated by turning a wheel on one side of
the machine.
• The wheel operation may be electrical / manual .
• The knife is fixed with its edge fixed upwards , while the object
moves against the knife .
• 1 rotation of the operating wheel produces , 1 complete cycle with a
downward cutting stroke & an upward return.
• It is often modified to cut ultrathin sections between 50Å – 200Å.

16. Advantages of the Rotary microtome
• Heavy & stable.
• Used for large number of serial sections .
• Ideal for Paraffin-embedded tissues .
• Movable knife holder .
• The sections cut are flat.
• It is useful for routine & research papers .
• Currently most common type of microtome in practice.

17. Base Sledge Microtome
• Large & heavy instrument .
• Very stable & popular for routine use .
• The feed mechanism has a fixed knife , beneath which , the object
mounted on a heavy sliding base moves .
• Mainly used for cutting sections of cellulose nitrate embedded tissues
with an obliquely set knife.

18. Parts of Base-sledge microtome
• Angular tilt adjustment
• Knife clamps
• Block holder
• Coarse feed adjustment
• Operating handle
• Thickness gauge
• Adjustment locking nut
• Block adjustment screw
• Split nut clasp

20. • The block holder is mounted on a steel carriage which slides backward
& forwards in groups against fixed horizontal knife .
• The block is raised towards the knife at a predetermined thickness.
Advantages of Base-sledge microtome
• Useful to cut extremely hard blocks & large sections ( eg : brain ).
• The microtome is heavy & stable.
• The knife used is sledge shaped which requires less honing.

21. CAMBRIDGE ROCKING
MICROTOME

22. • A simple machine invented by Sir Horace Darwin in 1881 .
• Developed by Cambridge company .
• The instrument has an arm that moves in a rocking motion while cutting the
sections.
• Hence named as Cambridge rocking microtome.
• The knife is held by means of microtome thread.
• The rocking microtome was designed primarily for cutting paraffin wax sections .
• When needed , it can also be used to cut frozen section tissues .

23. PARTS OF THE ROCKING MICROTOME
• Knife holder
• Block holder / chuck
• Upper & lower arms
• Screw
• Lever
• Pawl
• Ratchet wheel
• Mill head microtome screw
• Sleeve
• Scale

25. • It cuts the sections between 1 - 20 microns.
• The knife is fixed with the edge.
• The object moves against the knife circularly , producing a sharply curved
surface to the block .
• With each stroke the tissue holder automatically moves vertically towards the
knife.
• Cutting stroke is Spring operated & is easy to handle .
• This microtome must be placed on a solid non-slippery surface to allow a
better hold .

26. Advantages of Cambridge rocking microtomes
• The cost of knife & microtome is low.
• Celloidin embedded tissues can be sectioned easily.

27. VIBRATING MICROTOMES
• Cuts using a vibrating blade .
• The resultant cut is made with less pressure.
• Used for difficult samples .
• Thickness around 30 -500nm for fresh tissues & 10 – 500 nm for
fixed tissues .

29. SAW MICROTOME
• Used for hard tissues ( teeth & bones ).
• Has a recessed rotating saw which slices
through the sample .
• Minimal cutting thickness is 50 μm .

30. ULTRA MICROTOMES
• Designed to cut very thin sections .
• Parts :
Low power Binocular microscope .
object stage
• Has both manual / cutting actions.

31. How does it differ from conventional
microtomes ?
• Fine and precise feedback mechanism .
• Mechanical / thermally controlled
• Thickness range 5 – 100 nm
• Special knives - plate glass / plastic
• Can cut even small blocks .
• Can be used even in hard embedding media like araldite

32. Freezing Microtomes
• Designed for the preparing frozen sections of fluid & non-fluid tissue .
• Preliminary embedding is not needed .
• A cylinder of compressed carbon-dioxide for rapid cooling of the tissues is
connected with the object stage .
• Provisions to cool the knife is also present .
• The knife moves horizontally across the tissue surface .
• Characterstic features - Non-movable tissue block & cooling system.

33. Parts of freezing type microtome
• Knife clamps
• Operating handle
• Thickness gauge
• Stage
• Stage valve
• Coarse adjustment

34. Advantages of Freezing Microtome
• Used to cut sections for Rapid diagnosis .
• It cuts non-dehydrated fresh tissue in a frozen state.
• Used for Rapid histopathological diagnosis during surgery .
• This type of microtome is also used when lipids, enzymes, &
neurological structures are to be demonstrated.

35. DRAWBACKS OF FREEZING MICROTOME
• Inactivation of some enzymes
• Ribbon sections cannot be prepared using this microtome
• An inability to prepare multiple sections of uniform thickness .
Ultimately led to the invention of CRYOSTAT.

36. CRYOSTAT
• Pearse 1960 ; Hollands 1962 .
• Also called as Cold microtome / Deci-slicer in refrigerator .
• Device by which temperature can be maintained at low level .
• As described by Linderstorm – Lang and Mogeson ,
The cryostat consists of a microtome contained within a
refrigerated cabinet designed to operate at - 5 to - 30 ° C .

37. PROCEDURE
• Block tissue - up to 3 cm thick
Fresh tissue .
• Block is mounted in a small quantity of 1% glucose / water on the platform
of the chuck standing vertically on a bench .
• Immediately frozen - liquid carbon dioxide / solid carbon dioxide (dry ice).
• The chuck with frozen tissue is transferred to microtome maintained at -15 to
-20° C in the refrigerated chamber .
• The knife is moved & sections are cut at 4-5 μm with anti-roll guide plate
in position .

58. ADVANTAGES

59. In earlier models of
freezing microtomes ,
temperature controlled
manually
In Cryostat ,
temperature control is
automatic .

60. I DON’T NEED TO CHECK
THE TEMPERATURE OR
TISSUE THICKNESS..
That’s a relief !!

61. DISADVANTAGES
• Complete defrosting of machine is required from time to time.
• Slow fixation reaction .
• Cannot be used for fixed tissues.
• Not useful if the tissue requies lower temperature than the
setting temperature of the machine .
• Morphological details less accurate.
• Pigment formation is too prominent.
• Dermatitis of hand & irritation of nostrils to the microtomist.

62. In simple words ,
Microtome cuts a tissue
of only one millimeter
into million pieces …

65. Thank you