Introduction to Histology

Question 1

histology definition

Answer 1

the microscopic study of normal cells and tissues

Question 2

What is associated with disruption of normal structure and function?

Answer 2

Disease

Question 3

Pathology definition

Answer 3

the microscopic study of diseased cells and tissues

Question 4

What are the levels of structural organisation?

Answer 4

Cells, tissues, organs, body systems

Question 5

Definition of tissue

Answer 5

a group of similar cells working together to perform a particular function

Question 5

Definition of an organ

Answer 5

two or more different tissues interacting to perform a function

Question 6

Definition of organ system

Answer 6

A group of organs with related functions working together to perform a life function

Question 7

what are the 4 main tissue types?

Answer 7

Connective, epithelial, muscle, nervous

Question 8

Function of epithelial tissue?

Answer 8

Barrier and lining tissue e.g. outer layer of skin

Question 9

function of connective tissue?

Answer 9

provides structural and functional support e.g. bone, cartilage, (blood)

Question 10

Function of muscle tissue?

Answer 10

specialised for contraction e.g. cardiac cells

Question 11

function of nervous tissue

Answer 11

carries information throughout the body via electrical impulses e.g. nerves

Question 12

two methods of illuminating tissue samples

Answer 12

beam of light or electrons

Question 13

Which form of microscopy reveals ultrastructure?

Answer 13

Electron microscopy

Question 14

Resolutions of LM and EM

Answer 14

LM: 0.2uM
EM: 1nm (200 times greater)

Question 15

Which microscope is commonly used for routine histopathology?

Answer 15

LM

Question 16

Describe the stages required to collect and prepare tissues for histological examination

Answer 16

1. specimen collection
2. fixation
3. dehydration
4. embedding
5. sectioning
6. staining
7. viewing

Question 17

3 ways to obtain a specimen

Answer 17

incision or punch biopsy, needle biopsy, endoscoping biopsy

Question 18

What part of the body would punch biopsy be used for?

Answer 18

Skin/oral surfaces

Question 19

What part of the body is needle biopsy used for? How is it guided?

Answer 19

organs or lumps below the skin. Imaging techniques (MRI, Xray) are often used to guide the biopsy

Question 20

What part of the body would an endoscopic biopsy be used for?

Answer 20

Body part with a tract e.g. respiratory, alimentary, urinary tract.

Question 21

Description of endoscopic biopsy

Answer 21

a flexible tube with a light and camera. cutting tools can be used to collect tissue samples.

Question 22

What is the purpose of the fixation step in specimen preparation?

Answer 22

Preserves the structural arrangement between cells and extracellular components

Question 23

How does fixation preserve the specimen and prevent tissue decomposition?

Answer 23

terminates all biochemical reactions

Question 24

Examples of common fixatives

Answer 24

formaldehyde and glutaraldehyde

Question 25

Why do you need to dehydrate a specimen when preparing it?

Answer 25

Paraffin is used in the next step (embedding) and is not compatible with water

Question 26

How is a specimen dehydrated?

Answer 26

Gradually to prevent distortion using a series of graded alcohols. (water leaves sample via osmosis).

Question 27

Why is embedding required when preparing a specimen?

Answer 27

To support the tissue which allows thin sections to be cut

Question 28

What substances are commonly used for embedding?

Answer 28

Paraffin wax and resins

Question 29

During embedding, what substance is the alcohol (from dehydration) replaced with and why?

Answer 29

Alcohol is replaced with xylene because paraffin is not compatible with alcohol.

Question 30

What equipment is used to section an embedded specimen?

Answer 30

Microtome

Question 31

How thick should the specimen sections be?

Answer 31

approx 7uM

Question 32

Why is staining needed?

Answer 32

To make components visible and allow the identification of cell and tissue features

Question 33

Why must paraffin wax be removed and replaced with water before staining?

Answer 33

Most stains are aqueous and therefore not compatible with paraffin.

Question 34

How is paraffin wax replaced with before staining?

Answer 34

Reversal of dehydration steps - series of more diluted alcohol

Question 35

Which is the most commonly used stain?

Answer 35

Haematoxylin and eosin (H&E)

Question 36

How does H&E stain?

Answer 36

Haematoxylin is basic so stains acidic structures (nucleic acids) blue/purple. Eosin is acidic so stains basic structures (cytoplasmic proteins) pink/red.

Question 37

What does PAS stand for?

Answer 37

Periodic acid-schiff reaction

Question 38

What does PAS stain?

Answer 38

Complex carbohydrates are stained magenta e.g. mucins produced by goblet cells, brush borders, basement membranes.

Question 39

What structure does masson trichrome stain?

Answer 39

Connective tissues

Question 40

What colour are structures stained with masson trichrome

Answer 40

Nuclei (basophilic) - blue/purple
collagen - green/blue
cytoplasm, RBC, keratin - red

Question 41

Which stain utilises antibody-antigen specificity?

Answer 41

Immunohistochemistry

Question 42

How does immunohistochemistry staining work?

Answer 42

It uses antibodies complementary to the antigens of the desired structure. The antibodies are bound to an enzymatic or fluorescent indicator.

Question 43

What does alcian blue stain?

Answer 43

Mucin and cartilage stained blue

Question 44

what does van Gieson stain?

Answer 44

Collagen - red
nuclei, erythrocytes and cytoplasm - yellow

Question 45

what does reticulin stain?

Answer 45

reticulin fibres (component of CT) stained blue/black. Usually combined with H&E

Question 46

Which staining technique can be used to reveal information about the functional properties of cells?

Answer 46

Immunhistochemistry can be used to identify individual cellular proteins and so conveys functional information about cells.