Intro To Histology

Question 1

What is histology?

Answer 1

The microscopic study of normal cells and tissues

Question 2

What is disease typically associated with in relation to tissue structure and function?

Answer 2

Usually associated with disruption of normal tissue structure and function

Question 3

That is pathology?

Answer 3

The microscopic study of disease cells and tissues

Question 4

What is dysplasia of squamous cells?

Answer 4

Refers to abnormalities in squamous epithelium, the epithelium being the layer of cells that lines the cavity or surface in the body

Question 5

What are examples of physical and chemical insults that induce alterations in tissue architecture?

Answer 5

• Infection
• Extreme heat/cold
• Cuts or fractures
• Poison/drugs
• Genetic and congenital changes
• Aging, wear and tear
• Cancer

Question 6

What is required to visualise tissue structure?

Answer 6

Microscopes as cells are too small to see by the naked eye

Question 7

What 2 microscopes are used to look at tissue samples?

Answer 7

• Light microscope

- Electron microscope

Question 8

What does a light microscope reveal of the tissue?

Answer 8

Basic cellular structure

Question 9

What does an electron microscope reveal of the tissue?

Answer 9

Ultrastructure - structures only able to see through electron microscope

Question 10

Which microscope is most commonly used for routine histopathology?

Answer 10

Light microscope

Question 11

What are the 7 steps for making thin tissue samples for viewing?

Answer 11

1. Specimen collection
2. Fixation
3. Dehydration
4. Embedding
5. Sectioning
6. Staining
7. Viewing

Question 12

What are the 3 types of biopsy?

Answer 12

• Incision or punch biopsy
• Needle biopsy
• Endoscopic biopsy

Question 13

What is an incision or punch biopsy of?

Answer 13

Skin/oral surfaces

Question 14

What is a needle biopsy of?

Answer 14

Organs or lumps below the skin

Question 15

What is an endoscopic biopsy?

Answer 15

Flexible tube with light and camera. Cutting tools can be used to collect tissue specimens

Question 16

What imaging techniques are often used to guide biopsy?

Answer 16

X-ray, MRI

Question 17

What does fixation of tissue do?

Answer 17

• Preserves the structural arrangement between cells and extracellular components
• Terminates all biochemical reactions and so prevents tissue decomposition

Question 18

What are 2 common fixatives?

Answer 18

• Formaldehyde

- Glutaraldehyde

Question 19

What is dehydration of tissue to produce a tissue sample?

Answer 19

• Water is removed from tissue using a series of graded alcohols
• Water is removed gradually to prevent distortion

Question 20

Why does tissue need to be dehydrated for tissue sampling?

Answer 20

Since paraffin in immiscible with water, the main constituent of tissue, Samples need to be dehydrated by progressively more concentrated ethanol baths. This if followed by a clearing agent, usually xylene, to remove the ethanol. Finally molten paraffin wax infiltrates the sample and replaces the xylene

Question 21

What materials are most commonly used for embedding?

Answer 21

• Resins

- Paraffin wax

Question 22

Why does tissues for sample need to be embedded?

Answer 22

• Thin tissue sections are required for microscopy BUT most tissues are delicate and easily distorted, so tissues must be supported to allow thin sections to be cut

Question 23

Paraffin is not compatible with alcohol, so what is alcohol replaced with to allow embedding to occur?

Answer 23

Xylene

Question 24

What must the characteristics of tissue sections be?

Answer 24

• Thin and flat
• Ideally a single layer of cells
• Should be transparent

Question 25

What is a microtome?

Answer 25

• What embedded specimens are sectioned using

- A tool used to cut extremely thin slices of material

Question 26

What can tissue sectioning in different areas of the tissue cause?

Answer 26

Can make a big difference to tissue architecture

Question 27

Why do most cells need some sort of staining?

Answer 27

• Most of them are colourless and transparent
• Staining makes cells and their components more visible
• Allows the identifications of different cell and tissue features

Question 28

What is the composition of most LM stains?

Answer 28

• Aqueous

Question 29

Some stains for tissue examination are not compatible with paraffin, what needs to be done to fix this?

Answer 29

• Reversal of dehydration steps to remove paraffin wax and replace with water

Question 30

What is the most commonly used stain?

Answer 30

Haematoxylin and Eosin (H&E)

Question 31

What is haematoxylin?

Answer 31

A basic dye, which stains acidic structures (such as nucleic acids) BLUE/PURPLE

Question 32

What is eosin?

Answer 32

An acidic dye that stains basic structures (such as cytoplasmic proteins) RED or PINK

Question 33

What does periodic acid-Schiff reaction stain?

Answer 33

Complex carbohydrates MAGENTA (such as mucins, produced by goblet cells, brush borders and basement membranes)

Question 34

What does Masson trichrome stain?

Answer 34

• Stains connective tissues
• Nuclei and other basophilic structures stain BLUE
• Collagen stains GREEN/BLUE
• Cytoplasm, muscle, red blood cells ad keratin stain RED

Question 35

What is immunohistochemistry?

Answer 35

Refers to the process of detecting antigens in cells of a tissue section via antigen reveal. This is carried out by exploiting the principle of antibodies binding specifically to antigens in biological tissues

Question 36

How do you make permanent mounts of tissue samples?

Answer 36

• Stained sections are dehydrated once again to replace water with xylene
• Mounting medium and a coverslip seal to protect sections