Transcript MICROTOMES
MICROTOME MICROTOMES Microtomy Microtomy is the means by which tissues can be sectioned and attached to the surface so that examination by microscopy can take place. The basic instrument used in microtomy is a microtome into which cutting tool is clamped. Microtome is the instrument which is used to cut thin section of tissue. Microtome are machines that will advance an object for a predetermined distance then slide the object to the cutting tool. TYPES OF MICROTOME There are several types of microtome each designed for a specific purpose although many have a functional role. Excluding ultra microtome ,there are 5 basic types. named according to the mechanism. Rotary microtome Rocking microtome Rotary rocking microtome Base sledge microtome Sliding microtome Freezing microtome Parts: •Block holder •Knife clamps screws •Knife clamps •Block adjustment •Thickness gauge •Angle of tilt adjustment •Operating handle •Internal and external lock •This is the most commonly used microtome for routines and research purpose. The rotary microtome is so called because of the rotary action of the hand wheel actuates. These machines sometimes called minor microtome after their inventor prof. Minot. The rotary microtome is so called because of the rotary action of the hand wheel actuates. These machines sometimes called minor microtome after their inventor prof. Minot. This is the most commonly used microtome for routines and research purpose. Here the knife is fixed & the tissue blocks moves up & down vertically in front of the knife. Plane wedge knife is used. Thickness is adjusted by micrometer screws. The block moves forward to the knife at presented thickness during the rotation of fly –wheel handle. It has adjusting screws to make the tissue block parallel to the knife. ADVANTAGES It is heavier than rocking microtome. No vibration while cutting. It can be used for cutting hard tissues. The cutting angle of the knife is adjustable. The knife holder is movable. The ability to cope with very hard tissues , together with cutting good accurate section at 3mm gives the flexibility that is now required. Electrically driven microtome can be used when the necessary to produce ribbons for serial reactions required. This microtome are employed to their best advantage with resign embedded tissues. Manual or electrically driven rotary microtome are successfully used in cryostats. •It is the oldest type of microtome. •The name comes under the rocking action of the handle. •The Cambridge rocking microtome was the most popular microtome. •In this microtome knife is fixed &the block of the tissue moves through an arc to strike knife. DISADVANTAGES The size of the block that can be cut is limited. It is a righter microtome , so it vibrates white cutting. The cutting angle of the knife cannot be adjusted. The sections cut curved when the block moves through an arc. No serial section is possible. ROTORY ROCKING MICROTOME This is slightly more robust than the rocking microtome &has the advantage of producing a flat face to the tissue block. Although they can be used for paraffin wax work, they are used more commonly in cryostat. Most of them have retroactive mechanism which takes the tissue block away from the knife on the upward stroke. SLEDGE MICROTOME PARTS: Knife clamps Block holder Course adjustment Angular lift adjustment Operating handle Thickness gauge Adjustment rocking nut Block adjustment screw Split nut clamp It is used to cut large paraffin block tissues like eye ball ,lungs brain and also for cutting hard tissue It is a heavy microtome hence so stable Knife using is a plain wedge or Plano concave Here the block is faced towards knife at predetermined thickness It is also used for cutting colloid embedded section or block Freezing stage is available on this machine SLIDING MICROTOME In this type the knife is mode horizontally against a fixed block. It is mainly used for cutting celloidin embedded block & it is also used in paraffin backs embedding block. Used almost exclusively for electron microscopy Although other microtome can be modify for cutting frozen section, this type will give the best results & is used almost universally. This instrument has been designed to cut tissues which has not been fixed , processed or frozen. ADVANTAGES Greatest application in enzyme histochemistry & ultra structure histochemistry. Tissues are cut at very slow speed to avoid disintegration.