Process of removing excess wax after embedding. Excess wax is cut off from the block to expose the tissue surface in preparation for actual cutting.

The process by which a processed tissue is cut into uniformly thin slices (sections) to facilitate studies under the microscope

ROUTINE HISTOLOGIC PROCEDURE.

FROZEN SECTION

ELECTRON MICROSCOPY

25 mm in length. One side of the knife is flat while the other is concave.

120 mm in length. With both sides concave, recommended for cutting paraffin embedded sections on a rotary microtome

100 mm in length. Have both sides straight, recommended for frozen sections or for cutting extremely hard and tough specimens embedded in paraffin blocks, using a base sledge type or sliding microtome

are recommended for cutting celloidinembedded tissue blocks on a sliding microtome.

are used to cut paraffin sections on base sledge, rotary or rocking microtome

cutting facet, found on the tapered edge of all knives, the sides of which are more acutely inclined towards each other

the angle formed between the cutting edges. About 27˚ to 32˚.

sides of the knife are inclined at 15˚ angle maximum penetration of the tissues and minimize distortion.

the knife should be inclined with a 5-10˚ angle will prevent uneven sections and will prevent the cutting facet to compress the tissue block during the cutting process

“ralph knives’’ for ultramicrotomy

cutting resin section Steel knives

From HEEL TO TOE 20-30 TIMES Removal of nicks (irregularities) Hones (8 inch x 3 inch)

makes use of a vibrating frosted plate or wheel driven by an electrical motor.

removal of blemishes and grinding the cutting edge of the knife on a stone to acquire an even edge

for manual sharpening when cutting edge has been rendered blunt or nicked. This type usually gives the BEST RESULT

Gives more polishing effect than the belgium yellow

much coarser than the first two typed and used only for badly nicked knives. Followed by either one of the first 2 knife sharpeners

To polish and sharpen the cutting edge Removal of burrs From toe to heel direction Around 40-120 double strokes are usually required

made up of horse leather firmly attached to a solid back to prevent sagging

rocking and rotary microtome

sliding microtome Frozen section (Cryostat)

a spring balanced pawl is brought into contact with a ratchet feed wheel connected to a micrometer screw, which is rotated, moving the tissue block at a known distance towards the knife for cutting sections at uniform thickness 3 essential parts

the tissue is held in position

actual cutting of tissue sections

to line up the tissue block in proper position with the knife

Cambridge Rocking Microtome inventor: Paldwell Trefall in 1881 simplest among the microtomes

Minot Microtome inventor: Minot in 1885-1886 MOST COMMON type used today especially for paraffin-embedded tissues.

MOST DANGEROUS TYPE DUE TO MOVABLE EXPOSED KNIFE! inventor/developer: Adams in 1789

used for cutting sections for Electron microscopy. uses DIAMOND KNIVES, specimen is small, fixed in osmium tetroxide embedded in plastic

invented by Queckett in 1848