HT Tissue Processing

Question 1

What is the first step in tissue processing?

Accepted Answer

Fixation

Answer

Fixation is the critical first step in tissue processing, immediately following tissue collection. Its primary purpose is to rapidly preserve the tissue's cellular and molecular components, preventing autolysis (self-digestion) and putrefaction (bacterial decomposition). This step is essential for maintaining the tissue's architecture and integrity, which is crucial for accurate microscopic examination and diagnosis.

Question 2

Why is tissue dehydration important in processing?

Accepted Answer

It allows tissue to be infiltrated with embedding media.

Answer

Tissue dehydration is a crucial step where water is progressively removed from the tissue using ascending concentrations of alcohol. This is necessary because most embedding media, such as paraffin wax, are not miscible with water. By removing water, the tissue becomes receptive to subsequent clearing agents and ultimately allows for proper infiltration with the embedding medium, which is vital for sectioning.

Question 3

What is the purpose of clearing in tissue processing?

Accepted Answer

To make tissue transparent.

Answer

Clearing is the step after dehydration where alcohol is replaced by a clearing agent, such as xylene. The primary purpose of clearing is to make the tissue transparent, which is necessary because the refractive index of the clearing agent is similar to that of the embedding medium. This transparency allows for better visualization during embedding and ensures complete infiltration of the wax into the tissue.

Question 4

Which embedding media is commonly used in tissue processing?

Accepted Answer

Paraffin wax

Answer

Paraffin wax is the most commonly used embedding medium in routine histology due to its excellent sectioning properties and ease of use. It provides firm support to the delicate tissue, allowing for very thin sections to be cut without distortion or damage. While other media exist for specialized purposes, paraffin remains the standard for general diagnostic work.

Question 5

How does tissue fixation help preserve the sample?

Accepted Answer

By preventing cellular breakdown.

Answer

Tissue fixation preserves the sample by rapidly halting all cellular processes, including autolysis (self-digestion by enzymes) and putrefaction (decomposition by bacteria). This prevents the breakdown of cellular components and maintains the tissue's structural integrity and molecular composition. Effective fixation is crucial for accurate microscopic examination and diagnosis, ensuring the tissue remains in a life-like state.

(HT) Histotechnician Certification Practice Test

(HT) Histotechnician Certification Practice Test

HT Tissue Processing