Intro to the use of Microscopes

Question 1

Clinical relevance of microscopy

Answer 1

Distinguish normal tissue from abnormal tissue

Question 2

How are tissues prepared for microscopy?

Answer 2

Fixation
Section
Shape
Staining

Question 3

Fixation

Answer 3

Denaturation of proteins - heat, chemicals (formaldehyde, glutaraldehyde, alcohol) and freezing

Question 4

Sections

Answer 4

Wax and tissue placed on slides
Section taken
Remove wax with alcohol

Question 5

Shape

Answer 5

Depending on plane of section taken
Transverse: horizontal
Oblique
Longitudinal: vertical

Question 6

Staining

Answer 6

Haematoxylin: stains acid components of cell purple-blue
Basophilic, eg. Nuclei
Eosin: acidic dye, stains basic components of cell pink
Acidophilic, eg. Most of cytoplasm
Periodic Acid Schiff: oxidises sugars and stains resulting aldehydes
bright pink-purple from colourless
Trichrome: show up connective tissue and muscle
Other stain: Weigert’s elastin

Question 7

Magnification vs resolution

Answer 7

M: ability to make small objects seem larger
R: ability to distinguish two objects from each other

Question 8

How to focus microscope

Answer 8

Objective lens: x4, x10, x40
Coarse focus: low power
Fine focus: lenses are approx parfocal
Eyepieces: to suit your eyes interocular distance

Question 9

Convert 1um to mm

Answer 9

1um = 0.001 mm

Question 10

Illuminating the slide

Answer 10

Brightness control
Field diaphragm
Condenser
Condenser diaphragm 
Condenser focus control

Question 11

Routine setting up of microscope

Answer 11

1. Above the stage
   Set lamp brightness at low power; place slide on stage; focus specimen at low power using coarse then fine focus; adjust individual eyepieces and interocular distance
2. Below stage
   Close the field diaphragm; focus image of diaphragm using condenser; centre illumination; adjust condenser diaphragm so just brightest