MLT GlobeHistopathology: Microtomy & sectioning – page 3
49 Histopathology MCQs on Microtomy & sectioning with answers and explanations.
Cryostat sections of liver come off alternately thick and thin. The most likely cause is:
A dull blade compresses the block and then releases, causing alternating thick and thin sections. A loose block or blade does the same.
For cryostat sectioning, the anti-roll plate edge is positioned:
The plate should be parallel to and a hair above the blade edge so the section slides flat into the gap. Too high lets it curl; too low jams it.
In a cryostat, parts of the block fail to section and sections are incomplete. The most likely cause is:
Different tissues need different temperatures; too warm smears, too cold shatters and crumbles, leaving incomplete sections.
The angle between the blade's cutting facet and the block face, which prevents the knife from rubbing the block, is the:
The clearance angle (usually 3–8°) stops the facet contacting the block face. The bevel angle is between the two facets of the edge.
The bevel angle formed between the two facets of a microtome knife edge is typically about:
The bevel (cutting) angle is roughly 27–32°. The much smaller 3–8° figure is the clearance angle.
Which microtome knife angle stops the lower facet of the knife from rubbing and compressing the block face?
A small clearance angle (a few degrees) keeps the knife's under-surface off the block; zero clearance causes compression and alternate thick–thin sections.
The term 'slant angle' describes knife setting on which microtome?
On sledge microtomes the knife can be set obliquely (slanted) to the block's path, useful for large or hard blocks.
When cutting paraffin sections, the knife is set so that a small clearance angle separates the bevel from the block face. This angle is typically about:
A small clearance angle stops the knife bevel rubbing the block. Zero clearance compresses sections, while excessive angles cause chatter or scoring.
In the dry method of celloidin sectioning, the block is not kept in alcohol but is first cleared in which reagent before cutting?
For dry celloidin cutting, blocks are cleared in cedarwood oil so they can be sectioned without being flooded with alcohol. The wet method keeps blocks and knife moist with 70–80% alcohol.