Microtomy Flashcards
-Process by which the processed tissue is trimmed and cut unto uniformly thin slices or “sections” to facilitate studies under the microscope.
Microtomy
capable of cutting a section at a predetermined thickness by sliding the block into a cutting tool, usually a steel knife,
glass and diamond blade, which is fixed and attached to the machine.
-Microtome
3 Essential Parts of Microtome
- Block Holder
- Knife Carrier and Knife
- Pawl, Ratchet Feed Wheel and
Adjustment Screws
- where the tissue is held in position
Block Holder
- for actual cutting of tissue sections
. Knife Carrier and Knife
Pawl, Ratchet Feed Wheel and
Adjustment Screws
- to line up the tissue block in the proper position with the knife, adjusting the proper thickness of the tissue for successive sections
5 Kinds of Microtomes
- Rocking Microtome
- Rotary Microtome
- Sliding Microtome
- Freezing Microtome
- Ultrathin Microtome
- Cryostat or cold microtome
. Rocking Microtome
-for cutting serial sections of large blocks of paraffin embedded tissues
Rocking Microtome
-for cutting paraffin embedded sections
Rotary Microtome
for cutting celloidin embedded sections
Sliding Microtome
for cutting unembedded frozen sections
. Freezing Microtome
-for cutting sections for electron microscopy
Ultrathin Microtome
for cutting sections for Electron Microscope
Cryostat or cold microtome
-invited by Paldwell Trefall (1881)
Rocking (Cambridge) Microtome
Simplest microtome
Consist of: a. Heavy base
b. Two arms
Rocking (Cambridge) Microtome
Resting on pivots and supporting
column and attached the
micrometer screw at the base of
which is found the ratchet wheel
Lower Arm
Carrying the block holder on one
end by means of screw,
connected to a lever by a piece
of nylon thread
Upper Arm
-tissue cut in 10-12 u thickness
Rocking (Cambridge) Microtome
Rocking (Cambridge) Microtome is available in two sizes such as:
a. Small blocks of paraffin tissues
b. Large blocks of paraffin tissues
-theoretically not recommended for serial sections
. Rocking (Cambridge) Microtome
- not favored in most laboratories because of the restrictions in size
- There is difficulty in orienting the block.
Rocking (Cambridge) Microtome
-invented by Minot in 1885-86
Rotary Microtome
most common type used for both routine and research laboratories
Rotary Microtome
Electrically Driven Rotary Microtome also now available and can be ideally used when to produce ribbons for serial
sections
Rotary Microtome
- operated by rotation of the flywheel
* causing reciprocal motion of the knife over the block
Rotary Microtome
In rotary microtome, the thickness of the section is regulated by
ratchet feed wheel
used to come in contact with the ratchet wheel w/c in turn rotates the micrometer screw
Pawl
: make the block parallel to the microtome knife at all planes
Adjustment screws
-developed by Adams in 1789
Sliding Microtome
2 Types of Sliding Microtome
I. Base-Sledge Microtome
II. Standard Sliding Microtome
-consists of 2 movable pillars holding the adjustable knife clamps, allowing the knife to be set at an angle for
cutting celloidin sections.
Base-Sledge Microtome
-the chunk or block holder can be moved backward and forwards under the knife
Base-Sledge Microtome
- favored for hard and large blocks sectioning.
- sections are cut flat, allowing excellent serial sections
Base-Sledge Microtome
-the block remains stationary while knife is moved backward and forward
Standard Sliding Microtome
-mainly developed for cutting celloidin embedded tissue blocks
Standard Sliding Microtome
-more dangerous because of the movable knife
Standard Sliding Microtome
- Recommended for cutting extremely hard and rough tissue blocks
- It is the most dangerous type of microtome due to the movable exposed knife
Standard Sliding Microtome
-invented by Queckett in 1848
Freezing Microtome
-the stage for block holder is hollow and perforated around its perimeter
Freezing Microtome
- w/ flexible lead pipe thru CO2 passes from a cylinder
- lever operated valve allows the release of rapid and intermittent burst of CO2
- a cooling device for lowering the temperature of the knife to facilitate sectioning
Freezing Microtome
- It is used to cut undehydrated thin to semi-thin sections of fresh, frozen tissues, especially in instances when rapid
diagnosis is required.
-although other microtomes can be modified for cutting frozen section, this type will give the best results and is almost
used universally.
Freezing Microtome
-Used to cut:
a. undehydrated tissues for rapid diagnosis
b. histological demonstration of fats
c. for certain neurological structures
d. for sensitive tissue constituents
damaged by heat
Freezing Microtome
-is a refrigerated apparatus used for fresh tissue microtomy
-consist of microtome (rotary microtome) kept inside a cold chamber w/c maintained the temperature between -5 to -
300C (ave. -200C) by an adjustable thermostat.
Cryostat or Cold Microtome
capable of freezing fresh tissues w/in 2-3 minutes
-Thermostat
-used for urgent biopsies for intraoperative diagnosis
Cryostat or Cold Microtome
-equipped with a glass or gem diamond knife is used to cut very thin sections( typically 60-100
nm)
-Examined using Transmission electron microscope
Ultrathin Microtome
-Primarily used for cutting tissue sections at 0.5 micra for electron microscopy
Ultrathin Microtome
-Cutting sections of 4 Micra
Cryostat or Cold Microtome
-The knife used to cut ultrathin sections is consist of broken plate glass
Ultrathin Microtome
Routine Cryostat sections are cut at what Temperature?
-20 Degrees Celsius
Which of the following microtomes is used for rapid processing?
Rotary
The most dangerous type of microtome:
Sliding
