The document outlines the process of tissue embedding for histological examination, detailing procedures of dehydration, clearing, infiltration, and embedding. Various embedding media such as paraffin wax, plastic resins, agar, gelatin, and celloidin are discussed, along with a routine timing schedule for manual and automatic processing. Additionally, it describes components of automatic tissue processors, enhancing reagent penetration and allowing for programmable control of processing schedules.

1. Processing of Various Tissues for
Histological Examination
Embedding, Dehydration, Clearing,
Infiltration, and Tissue Processing
Dr. Jagroop Singh
Phd Biochemistry
Government Medical College Amritsar

2. Embedding - Definition
• Embedding is the process of infiltrating tissue
specimens with a medium that provides
internal support, allowing the tissue to be
sectioned into thin slices for microscopic
examination.

3. Various Types of Embedding Media
• 1. Paraffin Wax: The most common medium,
providing good support and preservation.
• 2. Plastic Resins: Used for high-resolution
imaging and harder tissues.
• 3. Agar and Gelatin: Used for embedding
smaller and delicate tissues.
• 4. Celloidin: Used for large tissues and
neurological specimens.

4. Embedding Procedure
• 1. Dehydration: Removing water from the
tissue using increasing concentrations of
alcohol.
• 2. Clearing: Replacing alcohol with a
substance that is miscible with both alcohol
and embedding medium (e.g., xylene).
• 3. Infiltration: Saturating the tissue with the
embedding medium (e.g., paraffin wax).
• 4. Embedding: Placing the tissue in a mold
with the embedding medium and allowing it to
solidify.

5. Routine Timing Schedule for Tissue
Processing
• Manual Processing:
• 1. Dehydration: 70% alcohol (1 hour), 80% alcohol (1
hour), 95% alcohol (1 hour), 100% alcohol (2 hours).
• 2. Clearing: Xylene (2 changes, 1 hour each).
• 3. Infiltration: Paraffin wax (3 changes, 1 hour each).
• Automatic Processing:
• Programmed schedules vary depending on the tissue
type and processor model, typically ranging from 6-
12 hours.

6. Components & Principles of Automatic
Tissue Processors
• 1. Reagent Containers: Hold various solutions for
dehydration, clearing, and infiltration.
• 2. Tissue Cassettes: Securely hold tissue samples
during processing.
• 3. Vacuum and Pressure: Enhance the penetration of
reagents into tissues.
• 4. Heating Mechanism: Maintains optimal
temperature for paraffin infiltration.
• 5. Programmable Controls: Allow customization of
processing schedules for different tissue types.