MLT GlobeHistopathology: Microtomy & sectioning
49 Histopathology MCQs on Microtomy & sectioning with answers and explanations.
Paraffin section ribbons are smoothed out before being picked up on slides by floating them on:
Flotation on water a few degrees below wax melting point flattens wrinkles; xylene and alcohol would dissolve or harden the ribbon.
A surgeon needs an intraoperative diagnosis within minutes. Which instrument cuts the tissue?
A cryostat is a microtome in a refrigerated cabinet that sections frozen, unprocessed tissue quickly.
New slides can be made grease-free before use by soaking them in:
Acid alcohol dissolves grease and dirt; albumin is an adhesive, and water alone does not remove grease.
Routine paraffin sections for H&E are usually cut at a thickness of:
Thin 3–5 µm sections show single cell layers clearly; about 1 µm suits resin, and thick sections overlap cells.
Cutting thin slices from a paraffin block is called:
Microtomy is sectioning on a microtome; embedding makes the block and flotation spreads the ribbon.
Which microtome is used routinely for cutting paraffin sections?
The rotary microtome cuts serial paraffin ribbons; ultramicrotomes are for electron microscopy and vibratomes for unfixed tissue.
Why must paraffin sections be spread out after cutting?
The knife compresses the section; floating on warm water lets it expand to true size and flatten.
How is a paraffin ribbon best divided into short lengths of a few sections each?
A warm blade cuts through wax cleanly without crushing sections; fingers and scissors distort or stretch the ribbon.
A cryostat is essentially:
The cryostat keeps a rotary microtome, knife and specimen in a chamber held well below freezing so frozen tissue can be cut thinly. A heat extractor or freezing shelf is an accessory.
For most unfixed soft tissues, the cryostat chamber is typically set at about:
Most tissues cut well between about −15 and −20 °C. Warmer settings let tissue smear; very cold temperatures make it brittle, except for fatty tissue which needs colder settings.
OCT compound is applied around a tissue fragment on the cryostat chuck. Its role is to:
OCT (optimal cutting temperature) compound surrounds and supports tissue on the chuck and freezes with it, enabling sectioning. It is water-soluble and washes off during staining.
What is the function of the anti-roll plate positioned over the cryostat knife?
The anti-roll plate forms a narrow gap with the knife face so each section slides out flat. Incorrect adjustment causes rolling, folding or tearing.
Unlike paraffin sectioning, a cryostat normally produces:
Frozen sections do not adhere to each other, so each is picked up directly onto a slide. Paraffin sections ribbon and are floated on a warm water bath.
The instrument used to cut thin sections from a paraffin block is a:
Rotary microtomes cut paraffin sections, usually 3–5 µm. Processors infiltrate tissue and embedding centres orient it in moulds.
An intraoperative consultation requires a rapid diagnosis on unfixed tissue. Which instrument is used to cut the sections?
The cryostat freezes and cuts tissue within minutes, allowing a diagnosis during surgery. Paraffin processing takes many hours.
Which of the following is NOT a type of microtome?
Rotary, sledge, sliding, freezing and ultramicrotomes are recognized types. 'Scanning' refers to microscopy, not sectioning.
Which of the following is NOT used to freeze tissue for frozen sections?
Liquid nitrogen, chilled isopentane, dry ice and cryogenic sprays are all used to freeze tissue. Formalin vapour is a fixative, not a freezing agent.
A muscle biopsy is sent for enzyme histochemistry. How should it be handled?
Most enzymes are destroyed by formalin fixation and paraffin processing, so enzyme studies require fresh frozen tissue.
Bacteria or fungi appear on slides where they are not part of the tissue. The usual source is:
Water baths not cleaned and refilled daily grow organisms that stick to sections. Filtering stains removes that lesser source.
Routine paraffin sections in most histology labs are cut on which microtome?
The rotary microtome gives ribbons of 3–5 µm paraffin sections. Ultramicrotomes are for EM and sliding microtomes for celloidin or large blocks.