this ppt briefly describes the history, process of microtomy and microtome components.

1. Maan singh - 0221600132
Drishti singh - 0151600132
Sattwik das - 02916001320
crotomy & Microtomes
Microtomy &
Microtomes

2. INTRODUCTION
What is microtomy ?
• Microtomy is the technique
of cutting tissues in very
thin sections.
• This technique is used for
pathological and
histological studies.
• “mikros” means “small”
“temnein” means “to cut”
• Microtome- an instrument
used to cut extremely

3. HISTORY OF MICROTOMY
At the beginning microscopy slides were prepared
manually using razor blades. Due to this histological
studies were hindered because of human error in
cutting of the sections.
The first microtomy device was invented by sir George
adams jr. and shortly later on developed by Alexander
cummings in 1770s .
The previously hand held design was later developed
to be a table based Andrew pichard in 1835 which
reduced vibrations.
The present day microtome we see was is a model that
was developed and presented by Wilhelm his sr. and
Wilhelm his

4. MICROTOME features
• Microtome is an instrument used for
microtomy procedures.
• Microtomes consist of various parts
such as knives, base (microtome
body), and material of tissue holder.
• Other features are mostly type specific,
some features are present on some and
absent on others.

5. MICROTOMECOMPONENTS

6. KNIFETYPES
• Microtomes come in give various shapes –
I. planoconcave shape
II. biconcave shape
III. wedged shape
IV. chisel shape
• Based on material used blades can be distinguised into
four categories-
- steel, glass, diamond, disposable

7. ANGLE OF KNIVES

8. • Bevel angle is the angle between the two facets of the
cutting edge.
• 27-32 degrees
• Smaller the bevel angle sharper the knife, but too low
bevel angle can cause elastic distortion of the edge.
• High rake angle and low clearance angle gives less
compression to tissue block.

9. MICROTOME SHARPENING
METHODS
• Microtome knives are sharpened via a two step method,
by manual and automatic means.
• Two steps- honing and stropping.
• Honing- grinding the cutting edge of the knife on a hard
abrasive surface to sharpen the knife.
• Stropping- process of polishing an already fairly
sharpened knife edge.

11. TYPES OF MICROTOME
• Most popular types of microtome machines are listed
below
1. rotatory microtome
2. sledge microtome
3. vibrating microtome
4. saw microtome
5. laser microtome
6. Freezing microtome

12. ROTATORY MICROTOME
• The most frequently used version works in a rotating
manner.
• Machine body itself rotates around the blade.
• Produces tissue slices as thin as 1-60 micrometers.
This microtome
usually uses glass or
diamond knives
for cutting thin slices of
a given sample.

13. SLEDGE MICROTOME
• This microtome design Works by holding the sample still
in the “shuttle”, which then advances and retreats over
the blade.
• This design cuts tissues that are much tougher and are
therefore hard to slice .
• Majorly used to cut
bones
• and other difficult
material.

14. VIBRATING MICROTOME
• A vibrating blade is the defining characteristic of this
machine.
• This allows tough and hard samples to be cut without
applying the pressure that another mechanism, with a
stationary blade, would instill.
• This mechanism can produce sample slices
as thin as 30 – 50 micrometers.

15. SAW MICROTOME
• Similar to a sledge
design, this type of
microtome is used when
materials are extremely
hard, like bones or teeth,
and require more force.
• A rotating saw is used
to slice which can
produce slices that are,
at a minimum 30
micrometers thick.

16. LASER MICROTOME
• A laser is used for
precise cutting without
actually touching the
sample.
• this machine enables
non-contact slicing
without causing thermal
damage.
• This automatic
microtome design can
cut slices with thickness
ranging from 10-100

17. FREEZING MICROTOME
• the tissue sample is
frozen and maintained in a
frozen state with liquid carbon
dioxide. It is useful for (rapidly)
obtaining sections of unfixed
soft tissue.
• The freezing microtome is
equipped with a stage upon
which tissues can be quickly
frozen.
• The knife is moved, whereas
the cutting block is kept static.

18. Why liquid carbondioxide ?
Liquid nitrogen has an extremely low
specific heat constant. The result is that
the contact between liquid nitrogen and
the tissue causes a vapour barrier that
builds up next to the tissue and greatly
slows the penetration of cold into the
tissue.

19. TISSUE RECIEVING
• Tissue received in surgical pathology contains specimen
details and patient information.
• The samples are received fresh or in liquid preservative
such as formalin

20. GROSSING
• Grossing is the process in which pathology specimens
are examined and trimmed to proper size, best part is
selected for further microscopic examination to obtain
diagnostic information.
• The tissue is now placed in small cassettes which hold
the tissue in and allow the fluids through the slits to
bathe the tissue in the fluids.

21. TISSUE FIXATION AND
PROCESSING
• The objective of tissue processing is to stabilize the
tissues or cells and preserve their morphological,
anatomical and biochemical characteristics for accurate
diagnosis.
• To achieve this the tissue smears are usually immersed
in fixative solutions.
• Most commonly used fixative is 10% neutral buffered
formalin

22. DEHYDRATION
• Water is found In tissues as free and bound form.
• Tissues are processed to the embedding medium by
removing free water.
• To minimize tissue distortion or shrinkage from
dehydrant, delicate specimens are dehydrated in a
series of ethanol – from 10%, 20%, 50%, 95%, 100%
ethanol.

23. CLEARING
• Since ethanol ad paraffin are not miscible, alcohol must
be replaced by an organic solvent that is miscible with
both paraffin and alcohol.
• The tissues are usually put through three changes of the
clearing agent and transferred to paraffin

24. SAMPLE EMBEDDING
• Tissues from the processor are still in the cassettes, then
transferred manually into the embedding molds.
• Tissues must be aligned properly at the bottom of mold
ad the bottom part of cassette containing ascession
number need to place over the mold
• The mold and cassette are then filled with more wax.
• The paraffin the allowed to solidify by putting the
embedding molds on a refrigerated surface .
• Once the paraffin is solid, the entire block with the
cassette is popped out of the mold and the block is ready
for the thin sectioning using the microtome

25. SECTIONING
Once the paraffin has solidified the tissue block is removed
from the mold ad placed o the microtome.
In the microtome due to the friction between the knife and
the microtome enough heat is generated with the cutting
action allows the tissue section to adhere with each new
section and forms a ribbon of sections.
The ribbon is floated on warm water bath to remove any
compression and wrinkles in the tissue caused by the
cutting .
The desired section is picked upon a glass slide and is then
is kept away for drying.

26. Thank
you