Question 1

Which of the following best describes fixation? A)A procedure adopted to kill, harden and preserve the tissue for microscopic study by the use of substances like xylene. B)A procedure adopted to kill, harden and preserve the tissue for microscopic study by the use of substances like mercuric chloride. C)The procedure in which the ionic materials are removed from the tissue. D)The process of removing intracellular and extracellular H₂O.

Accepted Answer

A procedure adopted to kill, harden and preserve the tissue for microscopic study by the use of substances like mercuric chloride.
Fixation is best described as a procedure adopted to kill, harden and preserve the tissue for microscopic study by the use of substances like aldehydes (formaldehyde and glutaraldehyde), metallic fixatives (mercuric chloride), lead fixatives and other compound fixatives. Xylene is not used as fixative but rather as a clearing agent for de-alcoholization in the embedding process. Letter C is the description of the procedure that removes calcium from the tissue called as decalcification and letter D is the description of the process of removal of water in the tissue called as dehydration.

Question 2

What are the characteristics of a good fixative?
A)It must inhibit bacterial decomposition and autolysis.
B)It must permit rapid and even penetration of tissues.
C)Both A and B
D)None of the above

Accepted Answer

both A and B
The characteristics of a good fixative must inhibit bacterial decomposition and autolysis as well as it must permit rapid and even penetration of the tissues. Because a good fixative preserves the cellular structures and prevent it from cellular disintegration. That is why it is needed that the fixative used must rapidly permit even penetration of tissues. Therefore, both A and B are correct.

Question 3

Which of the following is not an example of a nuclear fixative?
A)Flemming's fluid
B)Newcomer's fluid
C)Heidenhain's Susa
D)Orth's fluid

Accepted Answer

Orth's fluid
The examples of nuclear fixatives are Felmming's fluid, Newcomer's Fluid, Heidenhain's Susa, Carnoy's fluid and Bouin's fluid. These nuclear fixatives contain glacial acetic acid as their primary component due to its affinity for nuclear chromatin. They have a pH of 4.6 or less. Orth's fluid is an example of a cytoplasmic fixative that never contains the glacial acetic acid which destroys mitochondria and golgi bodies of the cytoplasm.

Question 4

Which of the following is the advantage of glutaraldehyde over formaldehyde as a fixative?
A)It is cheap and readily available.
B)It produces less tissue shrinkage.
C)It is compatible with many stains.
D)All of the above.

Accepted Answer

It produces less tissue shrinkage.
The advantage of glutaraldehyde over formaldehyde is that it produces less tissue shrinkage. This is because one of the disadvantages of formaldehyde is it causes significant tissue shrinkage. Moreover, glutaraldehyde is more expensive than formaldehyde and it is not readily available because it needs to be prepared. Formaldehyde is also the fixative widely used because of its compatibility with most stains.

Question 5

What is the ideal preparation or concentration of formaldehyde?
A)15% solution
B)3% solution
C)8% solution
D)10% solution

Accepted Answer

10% solution
The ideal preparation or concentration of formaldehyde used in the laboratory is that of a 5% and a 10% solution. Therefore, it must be diluted by 1:10 parts with distilled water for a 10% solution, and 1:20 parts with distilled water for a 5% solution. A 10% formaldehyde solution preserves a wide range of tissues and has the advantage of being a versatile fixative.

Question 6

What is the usual fixation time when using 10% formaldehyde?
A)3 hours
B)12 hours
C)24 hours
D)72 hours

Accepted Answer

24 hours
The usual fixation time when using 10% formaldehyde is 24 hours. This is because it produces excellent morphological detail. "Over fixing" the tissue with formaldehyde could complicate sectioning and impair the staining process. On the other hand, "under fixing" with formaldehyde can produce some artifacts because of its exposure to alcohol. Other durations in the choices are not good fixation times when using formaldehyde.

Question 7

What is the formula needed to prepare a 10% formol-saline?
A)100ml of 40% formaldehyde, 9g of NaCl, and 900ml of distilled water
B)100ml of 10% formaldehyde, 10g of NaCl, and 1000ml of distilled water
C)100ml of 5% formaldehyde, 11g of NaCl, and 1200ml of distilled water
D)100ml of 20% formaldehyde, 5g of NaCl, and 1500ml of distilled water

Accepted Answer

100ml of 40% formaldehyde, 9g of NaCl, and 900ml of distilled water
The formula needed to prepare 10% formol-saline is mixing 2 aqueous solutions of 100ml of 40% formaldehyde and 900ml of distilled water, and adding 9 grams of NaCl. The other preparations are false and inaccurate.

Question 8

What is the ideal concentration of ethyl alcohol used when fixing blood, tissue films and smears?
A)70% ethyl alcohol
B)75% ethyl alcohol
C)85% ethyl alcohol
D)95% ethyl alcohol

Accepted Answer

95% ethyl alcohol
The ideal concentration of alcohol used when fixing blood, tissue films and smears is 95% ethyl alcohol. If lower concentrations are used, there's a tendency that the red blood cells become hemolyzed and the white blood cells are inadequately preserved. Other concentrations of ethyl alcohol are not ideal for use when fixing blood, tissue films, and smears.

Question 9

This is the fixative that is considered to be the most rapid fixative.
A)Newcomer's fluid
B)Flemming's solution
C)Carnoy's Fluid
D)Formalin

Accepted Answer

Carnoy's Fluid
The fixative that is considered to be the most rapid fixative is Carnoy's fluid. This is due to the reason that Carnoy's fluid fixes and dehydrates the tissue at the same time. The fixation time is about 1-3 hours. Other fixatives stated above have longer fixation times.

Question 10

Which of the following is used as dehydrating agent and as a fixative at the same time?
A)Acetone
B)Mercuric Chloride
C)Acetic acid
D)Both A and B

Accepted Answer

Acetone
The substance that is used as a fixative and as a dehydrating agent is acetone. Acetone has been used as a dehydrating agent in tissue processing. It is rapid-acting in nature but makes the tissue much more fragile if it is exposed extensively to acetone. Recent developments have also utilized acetone as a fixative in a technique known to combine acetone, methylbenzoate, and xylene. This requires overnight fixation of tissues in acetone at -20 degree Celsius. Other choices do not possess these two qualities.

Question 11

What substance is added to formaldehyde in order to remove the precipitate produced by prolonged storage?
A)Acetone
B)Acetic acid
C)Methanol
D)Distilled water

Accepted Answer

Methanol
Methanol is the substance that is added to formaldehyde in order to remove the precipitate produced by prolonged storage. Methanol prevents its decomposition to formic acid but it serves to denature protein, thereby rendering formaldehyde unsuitable as a fixative for electron microscopy.

Question 12

It is used in fixing brain tissues for the diagnosis of rabies.
A)Heat fixation
B)Alcohol
C)Acetone
D)Osmic acid

Accepted Answer

Acetone
The fixative used in fixing brain tissue is acetone. This is because it preserves the brain tissue better and does not interfere with fluorescent immunoglobulin test. Other fixatives are not ideally utilized for fixing brain tissues.

Question 13

Which of the following retards fixation of tissues?
A)Smaller and thinner tissues
B)Agitation
C)Moderate heat at about 37-56 degree Celsius.
D)Presence of fat

Accepted Answer

Presence of fat
One of the substances that will retard fixation of tissues is the presence of fats. Fatty tissues are cut into thin sections and are fixed longer. Other options do not retard the fixation of tissues.

Question 14

On which of the following specimens do you primarily use Sudan stains?
A)nerve tissue
B)fat
C)muscle fibers
D)bone

Accepted Answer

Fat
Sudan stains are used for the purpose of staining and demonstrating fats such as triglycerides, lipids, phospholipids and lipoproteins since they have a high affinity to fats. Specific Sudan stains can be Sudan black and Sudan IV. The other three types of specimens are not effectively demonstrated by a Sudan stain.

Question 15

Heat fixation should be used on the following except for:
A)Gram stain
B)Capsular staining
C)Endospore staining
D)Acid Fast stain

Accepted Answer

Capsular staining
Heat fixation will cause a bacterium's capsule to shrink, making it difficult to view once it is already stained. Therefore, heat fixation is never to be used on capsular staining. Instead, the sample is air dried and a negative stain is used for visualization. All the other choices should undergo heat fixation.

Question 16

Which of the following is not a purpose of fixation?
A)Acts to disable proteolytic enzymes that digest or damage the sample
B)Protects the sample from extrinsic damage
C)Prevents autolysis or putrefaction
D)Decreases the mechanical strength or stability of cells and tissues

Accepted Answer

Decreases the mechanical strength or stability of cells and tissues
Fixation is not used for the purpose of decreasing the mechanical strength of cells and tissues. Instead, it is applied to increase mechanical strength and stability. All the other three choices are other purposes of fixation.

Question 17

Which of the following statements does not accurately describe formaldehyde?
A)It penetrates the tissues rapidly
B)Formaldehyde fixes tissue specimens at a rapid rate of about 1mm per hour.
C)It is an ideal fixative for nucleic acids
D)It is one of the most commonly used aldehyde fixative

Accepted Answer

It is an ideal fixative for nucleic acids
The use of formaldehyde as a fixative does not preserve nucleic acids. Therefore, making it an ideal fixative for nucleic acids is a false statement. All the other choices accurately describe formaldehyde.

Question 18

Which of the following properties of Mercuric chloride makes it restricted for use?
A)Toxic
B)Corrosive
C)Dangerous to the environment
D)All of the above

Accepted Answer

All of the above
All of the above answers are the properties of mercuric chloride that makes it restricted for use. Utilizing mercuric chloride has been restricted since it was found out that this compound is toxic to living organisms, it is very corrosive, and it is deemed dangerous to the environment.

Question 19

Which of the following properties of microwave fixation makes it unsuitable for use in large specimens?
A)Microwaves can damage fine tissue structures
B)Microwave fixation is ideally used for 10-12mm tissue blocks
C)Using microwaves increases the rate of autolysis
D)Microwave fixation inadequately heats the core of a large specimen without it significantly overheating the exterior portion

Accepted Answer

Microwave fixation inadequately heats the core of a large specimen without significantly overheating the exterior portion
The significantly potent heating property of microwaves makes it unsuitable for use in large specimens since it cannot adequately penetrate the center of large and thick specimens without overheating the external side of a specimen. Other choices do not address why microwaves are not used for large specimens.

Question 20

Which among the following is not a property of acetic acid?
A)It causes the shrinkage of collagen
B)It is an agent used for denaturation
C)It does not generally fix proteins
D)It is a precipitating fixative

Accepted Answer

It causes the shrinkage of collagen
Acetic acid does not cause the shrinkage of collagen but it swells collagen instead. The other statements are properties of acetic acid as well.

Quiz 1: Fixation

Which of the following best describes fixation?

What are the characteristics of a good fixative?

Which of the following is not an example of a nuclear fixative?

Which of the following is the advantage of glutaraldehyde over formaldehyde as a fixative?

What is the ideal preparation or concentration of formaldehyde?

What is the usual fixation time when using 10% formaldehyde?

What is the formula needed to prepare a 10% formol-saline?

What is the ideal concentration of ethyl alcohol used when fixing blood, tissue films and smears?

This is the fixative that is considered to be the most rapid fixative.

Which of the following is used as dehydrating agent and as a fixative at the same time?

What substance is added to formaldehyde in order to remove the precipitate produced by prolonged storage?

It is used in fixing brain tissues for the diagnosis of rabies.

Which of the following retards fixation of tissues?

On which of the following specimens do you primarily use Sudan stains?

Heat fixation should be used on the following except for:

Which of the following is not a purpose of fixation?

Which of the following statements does not accurately describe formaldehyde?

Which of the following properties of Mercuric chloride makes it restricted for use?

Which of the following properties of microwave fixation makes it unsuitable for use in large specimens?

Which among the following is not a property of acetic acid?