Histotechnology-I Notes
Subject Overview
Histotechnology-I introduces tissue processing for histopathology from specimen collection through to the finished stained slide — fixation and fixatives, decalcification, embedding and dehydration, section cutting and microtome technique, and staining theory and the routine Haematoxylin and Eosin and PTAH staining procedures. A 4-credit elective theory paper.
Subject at a glance
4
Units
31
Topics
4
Credits
4
Infographics
Unit-wise Syllabus
4 units — open any unit for detailed topic-wise notes, diagrams and important exam questions
- Introduction to histotechnology
- care and maintenance of laboratory equipment
- safety measures
- routine methods of tissue examination
- collection and transportation of specimens
- basic concepts of fixation
- simple/compound/special fixatives
10% neutral buffered formalin
Simple, routine
Most tissues: the standard fixative
Bouin's fluid
Compound (picric acid)
Testis, embryo, biopsies
Zenker's fluid
Compound (mercuric chloride)
Bone marrow, spleen
Carnoy's fluid
Alcohol-based
Glycogen, nucleic acids
Study guide
This unit introduces histotechnology: equipment care, safety, routine methods of tissue examination, specimen collection and transport and fixation, including simple, compound and special fixatives. Learn why formalin is the standard fixative and how long fixation takes.
- Criteria of a good decalcification agent
- decalcification technique and workflow
- types of decalcifying fluids (organic/inorganic acid, chelating agents, ion-exchange resins, electrophoretic decalcification)
- embedding media
- dehydration
- clearing and infiltration
- manual and automatic tissue processors
- 1Fixation
Preserve the tissue
- 2Dehydration
Graded alcohols remove water
- 3Clearing
Xylene removes alcohol
- 4Infiltration
Molten paraffin wax
- 5Embedding
Wax block cast in a mould
Study guide
You study decalcification (criteria, technique and types of fluid) and tissue processing: embedding media, dehydration, clearing, infiltration and manual and automatic processors. Learn the order of the processing steps and the reagent used in each.
- Equipment for sectioning
- microtome knives and sharpening (honing, stropping)
- types of microtome
- freezing microtome and cryostats
- faults in paraffin section cutting and remedies
- mounting sections to glass slides
Rotary
Routine paraffin sections
3–5 µm
Sliding
Large or hard blocks
Variable
Cryostat (freezing)
Frozen sections during surgery
5–10 µm
Ultramicrotome
Electron microscopy
Under 0.1 µm
Study guide
You study sectioning: microtome equipment, knife sharpening (honing and stropping), types of microtome, the freezing microtome and cryostat, common faults in section cutting and their remedies and mounting sections on slides. Learn the common cutting faults and how to correct them.
- Theory of staining
- classification of dyes and dye chemistry
- mordants and accentuators
- metachromasy
- use of controls
- stain and buffer preparation
- mountants
- nuclear and cytoplasmic stains
- manual and automatic staining
- Haematoxylin and Eosin staining
- Mallory's Phosphotungstic Acid Haematoxylin (PTAH)
- 1
Dewax in xylene
- 2
Rehydrate
Through alcohols to water
- 3
Haematoxylin
Nuclei stain blue
- 4
Differentiate and blue
Acid alcohol, then Scott's tap water
- 5
Eosin
Cytoplasm stains pink
- 6
Dehydrate, clear and mount
Study guide
You study the theory of staining, dyes and dye chemistry, mordants, metachromasy, controls, preparation of stains and buffers, mountants, nuclear and cytoplasmic stains and routine H&E and PTAH staining. Understand why haematoxylin stains nuclei and eosin stains cytoplasm.
Why Histotechnology-I Matters
Good histology slides depend on every step of tissue handling, and histotechnologists are in demand in pathology laboratories, hospitals and research centres.
How to Prepare for Histotechnology-I
- Learn the sequence from fixation to staining as a flowchart.
- Practise section cutting to achieve thin, wrinkle-free sections.
- Learn the cause and remedy of each common section-cutting fault.
Histotechnology-I: Frequently Asked Questions
Why is fixation done?
Fixation preserves tissue structure and prevents decay so that it can be processed and examined under the microscope.
What does H&E staining show?
Haematoxylin stains cell nuclei blue-purple and eosin stains cytoplasm and connective tissue pink.