MICROTOMY Flashcards
ESSENTIAL PARTS OF MICROTOME
- Block holder - where the tissue is hold in position
- Knife carrier and knife - for actual cutting of the tissue sections
- Pawl, ratchet feed wheel and adjustment crews - to line up the tissue block in proper position with the knife, adjusting the proper thickness of the tissue for successive sections
TYPES OF MICROTOME:
- Rocking microtome/Cambridge microtome
- Rotary microtome
- Sliding microtome
- Freezing microtome
- Ultrathin microtome
- Cryostat
For cutting serial sections of LARGE BLOCK OF PARAFFIN EMBEDDED tissues; Simplest among the different types of microtome
Rocking microtome/Cambridge microtome
Who invented the Rocking microtom?
Paldwell Trefall (1881)
For cuting PARAFFIN EMBEDDED sections; MOST COMMON type used for both routine and research laboratories
Rotary microtome
who invented the rotary microtome?
Minot (bet. 1885-1886)
For cutting CELLOIDIN EMBEDDED sections; MOST DANGEROUS type of microtome due to movable exposed knife
Sliding microtome
Types of sliding mcirotome:
- Base-sledge: Movable block, stationary knife
- Standard-slicing: Stationary block, movable knife
Who invented the sliding microtome?
Adams (1789)
For cutting UNEMBEDDED FROZEN SECTIONS that releases carbon dioxide that freezes tissues
Freezing microtome
Who invented the freezing microtome?
Queckett (1848)
For cutting plastic embedded sections for ELECTRON MICROSCOPE (EM)
Ultrathin microtome
Optimum working temperature of Cryostat:
-18 to -20C
Maintaining temperature of cryostat:
-5 to -30C (near -20C)
Classification of microtome knives
- Conventional steel knives
- Disposable knives
- Glass knives
- Diamond knife
Types of conventional knives:
- Plane concave (25 mm in length)
- Biconcave (120 mm in length)
- Plane-wedge (100 mm in length)
LESS CONCAVE SIDES are recommended for cutting __________________ tissue blocks on a sliding microtome
CELLOIDIN-EMBEDDED tissue blocks
MORE CONCAVE SIDES are used to cut ________________ on base-sledge, rotary or rocking microtome
PARAFFIN SECTIONS
Recommended for cutting PARAFFIN EMBEDDED SECTIONS on a ROTARY MICROTOME
Biconcave (120 mm in length)
Recommended for FROZEN SECTIONS or for cutting EXTREMELY HARD AND TOUGH SPECIMENS, using a base-sledge type or sliding microtome
Plane-wedge (100 mm in length)
MORE COMMONLY USED microtome knives nowadays since it is cheaper to use than conventional steel knives
Disposable blades
**MAGNETIC KNIVES - suitable use for CRYOSTAT
Used for trimming and SEMI-THIN “survey” sectioning of tissue blocks for ELECTRON MICROSCOPY
Glass knives
Used only for cutting ULTRA-THIN sections for electron microscopy
Diamond knife
Sharpening of the conventional steel-knives
1st step:
2nd step:
Sharpening of the conventional steel-knives
1st step: HONING (HARD SHARPENING)
2nd step: STROPPING (POLISHING)
Removal of GROSS NICKES on the knife to remove blemishes, and grinding the cutting edge of the knife on stone to acquire an even edge
HONING
Removal of BURR formed during honing and polishing of the cutting edge of the knife
STROPPING
Edge first, HEEL to TOE direction:
HONING
Edge last, TOE to HEEL direction
STROPPING
How many double strokes should be done in honing?
20-30 double strokes
How many double strokes should be done in stropping
40-120 double strokes
Dimension of hones:
8x3 inch
Dimension of strops:
3-4x18 inch
THREE TYPES OF HONES:
- Belgium yellow
- Arkansas
- Fine carborundum
type of hone that gives the BEST RESULT in honing
Belgium yellow
type of hone that gives BETTER and MORE POLISHING effect
Arkansas
Coarsest; type of hone for BADLY NICKED AND JAGGED knives
Fine carborundum
Lubricants to be used in honing:
- Soapy water
- Mineral oil
- Clove oil
- Xylene or Liquid paraffin
Stropping: uses paddle strop made of _______________ that are usually treated with _______________ or _____________ at the back and not the surface
Uses paddle strop made of HORSE LEATHER that are usually treated with VEGETABLE OIL or CASTOR OIL at the back and not the surface
ANGLES IN TISSUE CUTTING
Bevel angle
Clearance angle
Wedge angle
Angel formed between the cutting edge of the knife about 27-32 degrees
Bevel angle
Angle formed between the cutting edge of the knife and the tissue block, 0 to 15 degrees angultaion;
Clearance angle
Perfect and Optimum angle is:
15 degrees
To prevent uneven section, angle is:
5-10 degrees
Angle formed by the sides of the wedge knives, normally 14 to 15 degrees
Wedge angle
