The use of the microtome and the science of microtomy remains key in histology and anatomical pathology. The microtomist ( A Biomedical Scientist) who cuts tissue at ultrathin microns) uses the microtome to aid diagnosis and improve research. This lecture note highlights different types of microtome and also discuses principles and troubleshooting

1. MICROTOMY
Odega Kevin .I.
BMLS (Histopathology)
MSc. (Histopathology & Cytopathology)
(ASCPi Gyn Cytology)
University Of Benin Teaching Hospital,
Anatomical Pathology Department. Benin City, Nigeria

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Learning Objectives
At the end of this activity, participants will be able to:
 Define microtomy
 Understand a brief history of microtomy
 Know the parts of the microtome
 Name describe and differentiate the types of
microtome
 Describe rotary and sliding microtome operation
 Understand the care of microtome
 Discuss paraffin block or “chuck” preparation and
properties before cutting and sectioning

3. The Science Of microtomy 3
Learning Objectives
At the end of this activity, participants will be able to:
 Discuss the cutting or sectioning process
 Discuss the clearance angle
 Describe the floatation bath and discuss its
importance
 Know Mayer’s egg albumin and use of charged
slides for molecular pathology technique sectioning
 Discuss the problems encountered in section
cutting, causes and solutions

4. Microtomy is a technique which yields thin tissue sections
for microscopic examination of internal structure. After
embedding routine histological sections are cut using the
microtome.
The first microtome suitable for sectioning animal tissues
was constructed in 1848, with the popular Cambridge
Rocker (1885), Minot (1886), and sledge microtomes (1910)
manufactured later.
Paraffin wax for infiltration and support during sectioning
was introduced during the mid 1800s.
The Science Of Microtomy
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Microtomy Is A Science?
 Emphatically, YES!
The process as a
whole can be broken
down into distinct
stages that are each
comprised of specific
scientific principles

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MICROTOME
 Microtome is a mechanical
device used to cut extremely thin
slices of biological specimens
known as sections.
 Microtomes are used in
microscopy, allowing for the
preparation of samples for
observation under transmitted
light or electron radiation.
 Microtomes use steel, glass, or
diamond blades. Depending
upon:
1) the specimen being sliced.
2) the desired thickness of the
sections being cut

7. PARTS OF THE MICROTOME
All microtomes have the
following major parts;
Block holder; in which the tissue is
held in position
Knife carrier and the knife
Adjustment screws and rachet
device (feed wheel); that line up
the tissue in proper relation to the
knife and feed the proper thickness
of tissue for successive sections.
The microtome feeding mechanism
is graduated in microns (um).

8. 1. Steel blades are used to
prepare sections of animal
or plant tissues for light
microscopy histology.
2. Glass knives are used to
slice sections for light
microscopy and to slice very
thin sections for electron
microscopy.
3. Diamond knives are used to
slice hard materials such as
bone, teeth and plant
matter for both light
microscopy and for electron
microscopy.
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9. TYPES OF MICTROTOME
Based on the mechanism:
Rocking
Rotary Rocking
Sledge microtome
Rotary microtome
Cryomicrotome
Ultramicrotome
Vibrating microtome
Saw microtome
Laser microtome

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Rocking Microtome
 The use of rocking
microtome is common in
developing countries. It is
relatively inexpensive,
simple to operate,
practically maintenance
free, and it has the ability
to produce tissue sections
of high quality.

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Rotary Rocking Microtome
 The most rotary
microtome operates
with a screw feed; the
block moves up and
down, and the block
advances a preset
number of
micrometers with
each revolution of the
wheel, one section is
cut.

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Sledge microtome
 The celloidin-embedded sections
and large paraffin blocks are cut by
sliding microtome. It is not used in
routine histopathology. Sliding
microtome holds the block, and the
knife is moved along the horizontal
plane past the block face. As the
knife is returned to the starting
position, it completes each section
cycle and a screw feed causes the
block to be raised toward the knife
at a predetermined thickness.

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Rotary microtome
 The rotary microtome
is preferred for getting
serial sections. It is
delicate and designed
to cut extremely thin
sections. It is found in
most laboratories
where routine paraffin
and frozen sections
are the only
requirements.

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Cryo-microtome
 For the cutting of frozen samples,
many rotary microtomes can be
adapted to cut in a liquid-nitrogen
chamber, in a so-called
cryomicrotome setup. The reduced
temperature allows the hardness of
the sample to be increased, such
as by undergoing a glass transition,
which allows the preparation of
semi-thin samples. However the
sample temperature and the knife
temperature must be controlled in
order to optimise the resultant
sample thickness.

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Ultramicrotome
 It allows the preparation of extremely thin
sectionsThe typical thickness of these
cuts is between 40 and 100 nm for
transmission electron microscopy
Diamond knives (preferably) and glass
knives are used with ultramicrotomes.
 Both options enable fast and
safer alignment of knife and specimen,
and the programmable knife and cutting
movements make trimming easy, you
can automatically trim a specimen to a
predetermined level in the block face,
ideal for morphometric studies.
 Three dependent, built-in, brightness-
controlled LED light sources provide
outstanding illumination for top light,
back light, and specimen
transillumination.

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Vibrating microtome
The vibrating microtome
operates by cutting using a
vibrating blade, allowing the
resultant cut to be made
with less pressure than
would be required for a
stationary blade. The
vibrating microtome is
usually used for difficult
biological samples. The cut
thickness is usually around
30–500 μm for live tissue
and 10–500 μm for fixed
tissue.

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Saw microtome
The saw microtome is
especially for hard
materials such as teeth or
bones. The microtome of
this type has a recessed
rotating saw, which slices
through the sample. The
minimal cut thickness is
approximately 30 μm and
can be made for
comparatively large
samples.

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Laser microtome
Contact free slicing while
realizing the potential of digital
image processing in isolating
specific cells of interest of
heterogeneous tissues.
The resulted pure cell
populations are used for gene
expression analysis, allowing for
highly specific molecular
characterization, without the
interference of extraneous cells.
Digital slide scanner and image
processing mechanism, the cell
dissection becomes more
efficient

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Care of Microtome
 Dust accumulation must be
prevented by putting a cover
when not in use. Wipe the
moving parts regularly with
good neutral oil (e.g.
coconut oil) to lubricate and
avoid rust.After cutting,
clean frequently from
accumulated paraffin using a
soft brush with xylene.Never
adjust the screws too tightly
that they may cause
binding.

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Paraffin block or “chuck” preparation and
properties before cutting and sectioning
 The paraffin block is trimmed before the actual
cutting using a hand razor or sharp knife. It
should be as small as possible, the sides must be
parallel, and the tissue should be 1 – 3 mm from
the edge on all sides.
 Return the shavings to the wax oven and use
again. The block face should be parallel, and is
finally trimmed using the microtome. It should
expose all the tissue desired on the slide and
without scratch marks.

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Cutting or Sectioning Process
 For routine procedures,
sections are usually cut
between4 – 6 u in thickness.
The center of the knife
(blade) is the most desirable
place to cut.
 Many Scientist cool the block
face with an ice cube. The
cutting rhythm rate should
be regularly maintained.

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Tissue ribbon (ideally, the center
ribbon)
 Each time the block hits the knife
it leaves behind a cut section
which will slide onto the knife,
pushing the previous one ahead
to produce a “ribbon”.
 The top and bottom edges of the
block should be parallel,
otherwise the ribbon would
curve.
 The clearance angle(angle
between knife and block face)set
for best cutting is 5 – 10
degrees.

23. NSH Teleconference - The Science Of
Tissue Processing 23
Attaching the tissue on a
slide
 Creased sectionsThe sections tend to crease
slightly (wrinkle) on cutting; therefore they are
first flattened before they are attached on the
slide.

24. The slide maybe treated with
adhesive,
 (L to R) Tissue ribbon floated on
flotation bath, attaching the flattened
tissue on a slide.
 The tissue sections are floated on
flotation bath – a device with warm
shallow water maintained at about 46
degrees Celsius (10 degrees Celsius
below melting point of paraffin wax).
 This will float and flatten the ribbon. The
slide maybe treated with adhesive, not
to remove the sections from the slide
during staining.
 The most common adhesive is Mayer’s
egg albumin. Tissue sections on the
slides
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25. Problems encountered in section
cutting, causes and solutions
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27. Move or Change Blade
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31. Block not square with knife
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32. Tissue too thick when Processed
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Conclusion
The Microtome is an indispensible tool for
histopathological analysis. It’s the bedrock and
center focus for histological techniques and its
relevance will remain paramount in tissue
preparations.
There cant be histology without the microtome
The Science Of Microtomy