Questions and Answers
What is the purpose of using a series of ethanol solutions in tissue preparation?
What is the term for the process of displacing ethanol with a solvent that is miscible with both ethanol and paraffin wax?
What is the typical temperature at which a histological wax is liquid?
What is the purpose of the microtome in tissue preparation?
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What is the purpose of staining in tissue preparation?
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What is the term for the process of enclosing the tissue in an embedding mould?
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What is the primary purpose of fixation in slide preparation?
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What is the main component of the media layer in elastic arteries?
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What is the recommended formalin-to-specimen volume ratio for optimal fixation?
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Which layer of the muscular artery is well-developed and has a prominent internal elastic lamina?
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What is the purpose of biopsy and aspiration?
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What is the diameter range of larger or muscular arterioles?
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Why is it important to handle fresh tissue specimens carefully?
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What is the main function of arterioles?
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What is the purpose of in vitro histology?
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What is the layer of the arteriole that is made up of a thin network of collagen fibers?
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What is the characteristic feature of the media layer in muscular arteries?
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What is the purpose of dehydration in tissue preparation?
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What is the next structure in the blood vessel system after the terminal arterioles?
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What is the common fixative used for most tissue samples?
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What is the characteristic feature of the adventitia layer in elastic arteries?
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What is the time frame for adequate fixation of tissues?
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What is autoradiography used for?
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What is the purpose of enzyme histochemistry?
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What is the function of the enzymes secreted by osteoclasts?
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What is the main component of organic bone matrix?
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What can cause swelling and shrinkage of tissue components?
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What is a common artifact in tissue samples?
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What is the function of the periosteum?
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What is the main component of inorganic bone matrix?
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What is a characteristic of neurons?
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What are the two main types of cells in the nervous system?
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What type of bone is found in the inner part of bones and is more abundant in the epiphysis?
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What is the structure formed by the parallel layers of calcified type 1 collagen in compact bone?
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What is a property of the nervous system?
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What is the function of the endosteum?
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What is the abbreviation for Peripheral Nervous System?
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What is the outer covering of a bone?
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Study Notes
Histological Techniques
- Histological techniques are procedures used in the acquisition, processing, and viewing of histologic samples.
- If well carried out, they yield quality results.
Biopsy and Aspiration
- Biopsy is a method of acquiring tissue samples for study.
- A small portion of the specimen is excised with a sharp blade or a fluid specimen is aspirated with the aid of a needle.
- Fresh tissue specimens can come from various sources and can be easily damaged during removal from the patient or experimental animal.
- They should be handled carefully and fixed as soon as possible after dissection.
Fixation
- Slide preparation begins with the fixation of the tissue specimen to preserve tissue structure.
- The purpose of fixation is to prevent tissue autolysis and putrefaction.
- For best results, biological tissue samples should be transferred into a fixative immediately after collection.
- Most specimens are fixed in 10% neutral buffered formalin.
- The optimum formalin-to-specimen volume ratio should be at least 10:1 (e.g., 10ml of formalin per 1cm3 of tissue).
- This will allow most tissues to become adequately fixed within 6-24 hours.
Dehydration
- Water in a specimen must be removed before it can be infiltrated with wax.
- Dehydration is carried out by immersing specimens in a series of ethanol (alcohol) solutions of increasing concentration.
- Ethanol is miscible with water and progressively replaces the water in the specimen.
Clearing
- Wax and ethanol are largely immiscible.
- A solvent miscible with both ethanol and paraffin wax is used to displace the ethanol in the tissue.
- This stage in the process is called "clearing" and the reagent used is called a "clearing agent".
Wax Infiltration
- The tissue can now be infiltrated with a suitable histological wax.
- A typical wax is liquid at 60°C and can be infiltrated into tissue at this temperature.
- It is actually done in an oven.
Embedding
- The process of enclosing the tissue in the embedding mould.
- The mould is filled with melted wax and the specimen is placed on it.
- The embedding mould is used to orient the specimen well.
Sectioning and Mounting
- A microtome is used to slice thin tissue sections off the block in the form of a ribbon.
- The microtome can be pre-set to cut different thicknesses.
Staining
- Stains are dyes applied to tissue specimens to make them conspicuous and distinguishable from one another.
- A sample of culture is mounted on the slide for viewing.
Autoradiography
- Autoradiography is a technique that uses photographic film to determine where within a cell a specific radioactively labeled compound is at the time the cell is fixed and sectioned for microscopy.
Enzyme Histochemistry
- This is a method for localizing cellular structures using specific enzymatic activity.
- Examples of enzymes detectable are phosphatases, dehydrogenases, and peroxidase.
Artifacts
- Artifacts are the result of changes in a tissue's structure or the addition of new structure.
- They include swelling and shrinkage of tissue components, wrinkles in sections, tears in sections, air bubbles, and dust.
- These can result from poor fixation and/or dehydration techniques, poor sectioning technique, or poor technique during mounting of sections.
Nervous Tissue
- The nervous system is made up of two cell types: nerve cells (neurons) and glial cells (neuroglia).
- Neurons are excitable, independent anatomic and functional units with complex morphological characteristics.
Arteries
- Arteries are classified into two types: elastic arteries and muscular arteries.
- Elastic arteries have a relatively thin adventitia with a greater proportion of elastic fibers.
- Muscular arteries have a thicker adventitia with a smaller proportion of elastic fibers.
Arterioles
- Arterioles are the main regulators of peripheral vascular resistance.
- Contraction and relaxation of the smooth muscles present in the walls of the arterioles can alter the peripheral vascular resistance (or blood pressure) and the blood flow.
Capillaries
- Terminal arterioles are continued into a capillary plexus that pervades the tissue supplied.
- Capillaries have a thin wall that allows for the exchange of substances between the blood and the tissue.
Bone Matrix
- Bone matrix consists of two components: organic components (type 1 collagen, chondroitin sulfate) and inorganic components (calcium and phosphorus forming hydroxyapatite crystals).
- The bone matrix is acidophilic in H&E section and shows the collagen type 1 and the bone cells.
- The bundles of collagen in the matrix form parallel layers called bone lamellae.
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Description
This quiz covers the various methods and techniques used in histology, including in vitro studies, histological techniques, and biopsy and aspiration methods.
