Session 1 - Introduction To And Method Of Studying Tissues Of The Body

Question 1

What are the factors that should be taken into consideration when collecting tissue?

Answer 1

1. Time since ‘since’ death - tissue begins decays immediately after death
2. Atmospheric oxygen - the oxygen in the atmosphere causes oxidation of the tissue and thus causing it to break down
3. Sample size - the tissue sample needs to be large enough so that all that needs to be observed can be observed but not too large as that would cause it to not fixate properly
4. Temperature - high temperatures cause the fixative to penetrate the tissue much faster but the rate of decay also increases. Lower temperatures decrease the rate of decay but cause the fixative to penetrate the tissue much slower.
5. Light - visible light, uv light and infrared light cause damage to the tissue
6. Type of test, stain and fixative - the type of test that will be conducted will influence the type of stain or dye and fixative used.

Question 2

Name the steps of tissue preparation

Answer 2

Collection
Fixation
Cutting into sections
Mounting on microscope plate
Staining/contrast
Investigating with microscope

Question 3

What is the purpose of tissue fixation?

Answer 3

To:

1. Terminate cell metabolism
2. Prevent enzymatic degradation of cells and tissues by autolysis
3. To kill pathogens
4. To harden the tissue

Question 4

What does tissue fixation entail?

Answer 4

It is composed of two parts, processing and embedding.

During processing, the cell is dehydrated so as to allow the embedding medium to adhere and stay inside the cells of the tissue as it is not water-based.

During embedding the cell is impregnated with the embedding medium to allow the tissue to be embedded, then the tissue is embedded.

Question 5

Name 3 fixatives

Answer 5

Formalin
Alcohol
Permanganate

Question 6

Why is it necessary for tissues to be stained?

Answer 6

Tissues are typically colourless and so observing the various structures in cells is nearly impossible. Staining the tissue adds colour and contrast to the cells and allows for the observation of individual structures in cells.

Question 7

Explain acidic stain/dye

Answer 7

It a has a nett negative charge and reacts to cationic groups in tissue (acidophylic tissue) and therefore stains acidophylic tissue.

Question 8

Explain basic stain/dye

Answer 8

It has a nett positive charge and reacts to anionic groups in tissue (basophylic tissue) and therefore stains basophylic tissue.

Question 9

What is basophylic tissue?

Answer 9

Tissue that has an acidic pH. Acidic tissue.

Question 10

What is acidophylic tissue?

Answer 10

Tissue that has a basic pH. Basic Tissue.

Question 11

List examples of acidophylic tissue.

Answer 11

Cytoplasm
Most intracellular organelles
Extracellular fibres (e.g collagen)

Question 12

List examples of basophylic tissue

Answer 12

Heterochromatin
Nucleoli
Ergastoplasma (ribosomes, rRNA)
Cartilage matrix (sulphate groups)

Question 13

Name 3 examples of acidic stains/dyes

Answer 13

Eosin
Acid fuchsin
Anilin blue

Question 14

Name 3 examples of basic stains/dyes.

Answer 14

Hematoxylin
Methyl green
Pyronin G

Question 15

Name 3 components that are visible without staining.

Answer 15

Pigments:

Haemoglobin
Melanin
Myoglobin

Question 16

Name 6 components that are lost during tissue preparation

Answer 16

1. Lipids and cholesterol
2. Small proteins
3. Small nucleic acids
4. Glycogen
5. Ions
6. Glucose

Question 17

What may be the reason that some components are lost during tissue preparation?

Answer 17

They may be washed out of the cells during the process of fixation.

Question 18

Give the reasons why some components are not visible with the light microscope.

Answer 18

1. Components were not part of the tissue to begin with
2. Components are lost during fixation
3. Components are not stained
4. Components are not stained differently from the surrounding structures/tissue and thus blend in
5. The resolving power of the microscope is too low.

Question 19

What is resolving power?

Answer 19

The ability of an optical system to produce separate images of closely positioned objects.

The shortest distance between 2 dots, where the 2 dots are visible as separate objects.

Question 20

Name the structures that are visible with light microscope.

Answer 20

Cytoplasm
Some mitochondria

Question 21

List the three methods of staining.

Answer 21

1. Immersion of tissue in stain or dye
2. Injection of tissue sample with stain or dye
3. Injection of living animal with stain or dye

Question 22

What is the effective resolution obtainable by a light microscope?

Answer 22

0,2 micrometers

Question 23

What is the effective resolution obtainable by the human eye?

Answer 23

0,2 mm

Question 24

What is the effective resolution obtainable by an electron microscope?

Answer 24

0,05 - 1 nanometer

Question 25

What is another term for acidophylic?

Answer 25

Eosinophilic

Question 26

What is the most used acidic stain?

Answer 26

Eosin

Question 27

What is the most used basic stain?

Answer 27

Hematoxylin