Methods In Light Microscopy

Question 0

What are the four classifications of tissues?

Answer 0

Epithelial tissue, connective tissue, nervous tissue, muscle tissue.

Question 1

What is a tissue?

Answer 1

A collection of cells specialised to perform a particular function

Question 2

What is the value of histology in diagnosis?

Answer 2

Can give a definitive diagnosis for conditions like cancer and Crohn’s disease (ulcerative colitis)
Can inform therapies by giving specific information on the type of disease and tissues involved.

Question 3

What is the relationship between milli, micro and nano meters?

Answer 3

1mm=10^-3m
1um=10^-6m
1nm=10^-9m

Question 4

What is the average diameter of a human cell?

Answer 4

10-20um

Question 5

What is the diameter of an oocyte?

Answer 5

100um

Question 6

What is the diameter of a red blood cell?

Answer 6

7.2um.

Question 7

What is a biopsy?

Answer 7

The removal of a small piece of tissue from an organ or part of the body for microscopic examination.

Question 8

What would a smear biopsy be used for?

Answer 8

Cervix or buccal cavity

Question 9

What would a curretage biopsy be used for?

Answer 9

Endometrium.

Question 10

What would a transvascular biopsy be used for?

Answer 10

Heart, liver

Question 11

What would a needle biopsy be used for?

Answer 11

Brain, breast, liver, kidney, muscle

Question 12

What tissues would be biopsied using direct incision?

Answer 12

Skin, mouth, larynx.

Question 13

What tissues would be biopsied using endoscopy?

Answer 13

Lung, intestine, bladder.

Question 14

What is used to cut thin slices of a specimen embedded in wax?

Answer 14

Microtome and steel blade.

Question 15

Why do tissues need to be fixed?

Answer 15

It cross links macromolecules which preserves cellular structure, prevents autolysis and putrefaction.

Question 16

What two fixatives can be used?

Answer 16

Glutaraldehyde, formaldehyde.

Question 17

What is the process by which a fixed biopsy is embedded in and impregnated with wax?

Answer 17

Dehydration - ethanol replaces water
Clearing - xylene or toluene replace ethanol
Embed in wax at 56 degrees Celsius.

Question 18

Describe the process by which a specimen embedded in wax becomes a stained histological slide

Answer 18

Section it.
Rehydrate it (xylene->ethanol->water)
Stain it (most stains water soluble)
Dehydrate it (water->ethanol->xylene)
Mount it

Question 19

What does haematoxylin stain and what colour?

Answer 19

Acidic components of cells purple (nucleolus, chromatin)

Question 20

What does eosin stain and what colour?

Answer 20

Basic components of cells pink (cytoplasm, extracellular fibres)

Question 21

What does the Periodic Acid-Schiff method stain, and what colour?

Answer 21

Carbohydrates and glycoproteins magenta (for example mucous)

Question 22

What stains elastic fibres?

Answer 22

Weigert’s elastin.

Question 23

What does Elastic Van Gieson stain, and what colour?

Answer 23

Muscle yellow
Collagen pink/red
Elastin blue/black

Question 24

What are three possible sections?

Answer 24

Oblique, transverse, longitudinal.

Question 25

What is the advantage of phase contrast microscopy?

Answer 25

Can see detail in living cells

Question 26

What can dark field microscopy be used for?

Answer 26

Diagnosis of syphilis and malaria

Question 27

What is fluorescence microscopy?

Answer 27

Use antibodies to fluorescently stain particular components of the cell.

Question 28

When is confocal microscopy used, and what does it eliminate?
What can it be used for, why?

Answer 28

Used to image tissues that have been labelled with fluorescent probes.
Eliminates out of focus flare.
Can section tissue in non invasive way, image living specimens.