Introduction to Feed Mechanism
In histology, the feed mechanism is crucial for preparing tissue samples for microscopic examination. It involves the precise movement and positioning of tissue specimens during sectioning to produce thin, consistent slices. Understanding this mechanism is essential for ensuring accurate and high-quality histological analysis.What is a Feed Mechanism?
The feed mechanism in histology refers to the method by which the tissue block is advanced towards the cutting edge of a microtome. This is done in controlled increments, allowing for the production of thin, uniform sections of tissue. The primary goal is to achieve sections that are thin enough to allow light to pass through for microscopic examination, typically in the range of 4-10 micrometers.
Types of Microtomes
There are several types of microtomes used in histology, each with a different feed mechanism:1. Rotary Microtome: This is the most common type used for routine histology. It uses a wheel to advance the tissue block towards the blade.
2. Sliding Microtome: Ideal for cutting larger or harder specimens. The tissue block is held stationary while the blade slides across it.
3. Cryostat Microtome: Used for cutting frozen sections. It has a cooling chamber to keep the tissue frozen, allowing for thin sections without thawing.
4. Ultramicrotome: Used for cutting ultra-thin sections for electron microscopy.
How Does the Feed Mechanism Work?
The feed mechanism works by advancing the tissue block in small, precise increments. This is achieved through various mechanical components, such as:
- Feed Screw: A threaded rod that moves the block holder forward.
- Ratchet Mechanism: Controls the incremental movement with each turn of the handle or wheel.
- Stepper Motor: In automated microtomes, a motor provides precise control over the feed increments.
1. Precision: Ensures consistent section thickness, which is vital for uniform staining and accurate diagnosis.
2. Reproducibility: Allows for multiple sections to be cut from the same block with minimal variation.
3. Efficiency: Speeds up the sectioning process, allowing for quicker turnaround times in diagnostic labs.
Common Issues and Troubleshooting
Despite its importance, the feed mechanism can encounter several issues:- Inconsistent Sections: Can be caused by worn feed screws or ratchets. Regular maintenance is essential.
- Block Slippage: May occur if the block holder is not securely tightened. Always check the holder before sectioning.
- Blade Dulling: A dull blade can tear the tissue instead of cutting cleanly. Regularly replace or sharpen blades.
Maintenance of Feed Mechanism
Proper maintenance is vital for the longevity and accuracy of the feed mechanism:- Lubrication: Regularly lubricate moving parts to reduce friction and wear.
- Cleaning: Keep the microtome clean and free of debris to prevent jamming.
- Calibration: Periodically check and calibrate the feed mechanism to ensure accuracy.
Conclusion
The feed mechanism is a fundamental aspect of histology, playing a crucial role in the preparation of tissue sections. Understanding its function, types, and maintenance can significantly impact the quality of histological analyses. Regular upkeep and troubleshooting can help mitigate common issues, ensuring reliable and consistent results in histological examinations.
