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Histology > Histology - Overview and Staining methods > Flashcards

Histology - Overview and Staining methods Flashcards

1
Q

what are the 4 main building blocks of life

A
  • proteins
  • lipids
  • nucleic acid
  • carbohydrates
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2
Q

what is histology

A

a microscopic study of normal cells and tissues, looking at how structure is related to tissue function, and how disease is associated with disruption of normal cell structure and function

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3
Q

what is pathology

A

a microscopic study of diseased cells and tissues

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4
Q

what are the 4 main tissue types

A

epithelial
connective
muscle
nervous

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5
Q

what are the two main methods of microscopy

A

light microscopy and electron microscopy

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6
Q

what is light microscopy

A

low resolution microscopy used to view basic cell structure

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7
Q

what is electron microscopy

A

method for viewing the ultrastructure of the cell

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8
Q

what is the microscopy technique used in routine histology

A

light microscopy

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9
Q

what are the steps to microscopy

A
  • specimen collection
  • fixation
  • dehydration
  • embedding
  • sectioning
  • staining
  • viewing
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10
Q

why are tissue samples cut into thin sections prior to the microscopy

A

most tissue samples are too thick to be examined directly under a microscope and must first be cut into very thin sections to enable light or electrons to pass through the tissue and make the structure visible

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11
Q

what are the different technique to specimen collection

A
  • incision or a punch biopsy
  • needle biopsy
  • endoscopic biopsy
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12
Q

what are incision or punch biospies used for

A

specimen collection from skin or oral surfaces

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13
Q

what are needle biopsies used for

A

specimen collection from organs or lumps below the skin. to guide the biopsy, imaging techniques like x rays and mris can be used

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14
Q

what does endoscopic biopsy involve

A

a flexible tube with light and a camera - cutting tools can be used to collect tissue specimens

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15
Q

where would an endoscopic biopsy be used in the body

A
  • trachea
  • bronchus
  • lungs
  • esophagus
  • stomach
  • small intestine
  • colon and rectum
  • mainly bladder
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16
Q

where would a needle biopsy be used

A

the brain
eye
thyroid
lymph nodes
breast
lung and pleura
liver
kidney
bone and bone marrow
testis
skeletal muscle

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17
Q

what kind of biopsy is used for the heart and the liver

A

transvascular biopsy

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18
Q

what do cells release as they die

A

enzymes that degrade components for the tissue

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19
Q

what does fixation do

A

terminates all biochemical reactions and so prevents the release and activity of degradative enzymes as well as inhibiting microbial growth and so prevents tissue decomposition

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20
Q

what are some common fixatives

A

formaldehyde and glutaraldehyde

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21
Q

why is fixation important during microscopy

A

it preserves the structural arrangement betwen cells and extracellular components

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22
Q

is paraffin embedding compatible with water

A

no

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23
Q

how is water removed from tissues during dehydration

A

using a series of graded alcohols, done gradually to be prevent distortion

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24
Q

why should water not be removed from the tissue sample in a single step

A

the tissue would shrink rapidly and the structural arrangement would be distorted

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25
Q

why do tissues require embedding

A

thin tissue sections are delicate and soft and easily distorted, and must be embedded in a hard substance as support

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26
Q

what are most commonly used to embed tissue samples

A

resin and paraffin

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27
Q

what are tissue samples submersed in prior to embedding and why

A

resin and paraffin are not compatible with water or alcohol, so after dehydration the sample is then immersed for a period of time in a strong solvent like xylene to replace the alcohol

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28
Q

how should tissue be cut to be viewed under a microscope

A

thin and flat, ideally just a single layer of cells

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29
Q

why should tissue samples be cut into thin and flat sections

A

so they are transparent, as this allows the beam of light or electrons to pass through the tissue to enable visualisation

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30
Q

how are embedded speciments sectioned

A

using a microtome

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31
Q

what is a microtome

A

a machine that cuts embedded tissues into sections around 7 nanometres thick

32
Q

what are tissue sections mounted on

A

glass slides

33
Q

why are tissue sections mounted on glass slides

A

for protection

34
Q

why is staining another important step in microscopy

A

most cells are colourless and transparent, so staining makes cells and their components more visible

35
Q

is there a limited number of staining methods available for light microscopy

A

no there is a wide variety

36
Q

what does staining allow

A

identification of different cell and tissue features

37
Q

what state are most stains for light microscopy

A

aqueous

38
Q

are stains compatible with paraffin

A

no

39
Q

why are stains not compatible with paraffin

A

they are aqueous

40
Q

how do you use stains incompatible with paraffin

A

reversal of the dehydration steps used earlier, so the embedded sample is first submerged in xylene before then being passed through the graded series of alcohol in order to replace the alcohol with water and leave it ready for staining

41
Q

does where the tissues are sectioned make much of a difference to tissue architecture

A

yes

42
Q

what is the most commonly used staining technique

A

haematoxylin and eosin (H&E)

43
Q

what is haematoxylin

A

a basic dye that stains acidic structures like nucleic acid blue/purple

44
Q

what is eosin

A

an acidic dye that stains basic structures such as cytoplasmic proteins red or pink

45
Q

are epithelial tissues highly cellular

A

yes - there is very little extracellular material

46
Q

what is the periodic acid-schiff reaction (PAS)

A

a method that stains complex carbohydrates magenta

47
Q

what are mucins produced by

A

goblet cells

48
Q

what are examples of PAS-positive molecules

A

muines produced by goblet cells, brush borders and basement membranes

49
Q

what is the proximal convoluted tubule

A

part of the nephron in the kidney. involved in reabsorption of essential nutrients and water to prevent them being excreted within urine

50
Q

why does the proximated convoluted tubule require a large surface area

A

it is involved in reabsorption of essential nutrients and water

51
Q

what does the PAS staining method reveal in the proximated convulated tubule

A

the prominent brush border projecting into the lumen of the tubule, as well as the basement membrane, as both are strongly PAS positive.

52
Q

what is the oesophagus

A

a strong muscular tube that conveys food from the throat to the stomach

53
Q

how is the mucosa found when in a relaxed state

A

deeply folded

54
Q

what do the different colours of masson trichrome represent

A

the blue purple colour is the nuclei, and other basophilic structures

the green blue is collagen

the red is the cytoplasm, muscle, red blood cells and keratin

55
Q

explain the immunohisotochemistry technique for staining

A

utilises antibody specifity for antigen. antibodies are required to identify substances of interest. the antibody is conjugated to an indicator, whether enzymatic or fluorescecnt

56
Q

what is the most specific staining method

A

immunohistochemistry

57
Q

what does immunohistochemistry use antibodies to do

A

stain specific cellular proteins by using antibodies specific for their antigen to reveal the components by joining the antibody to some sort of colour indicator

58
Q

what is the alcian blue staining method

A
  • stains mucin and cartilage blue, and can be combined with other stains like H&E
59
Q

what is the van gieson staining technique

A

stains collagen red, nuclei and erythrocytes and cytoplasm yellow

60
Q

what are reticulin fibres components of

A

connective tissue

61
Q

what is the reticulin stain

A

this stains reticulin fibres blue black, and is often combined with H&E

62
Q

what is the most common form of methods used in histology

A

light microscopy

63
Q

how can light microscopy be subdivided

A

bright field, immunofluorescence and dark field microscopy

64
Q

give a breakdown of periodic acid schiff

A

this is a method that stains complex carbohydrates a dark red or magenta. it identifies glycogen in cells

65
Q

what are the main steps to preparing tissue for bright field microscopy

A
  • fix the tissue using formalin
  • process the tissue (remove water with ethanol, remove ethanol with xylene. embed in paraffin - removes xylene)
  • section
66
Q

what happens once the paraffin embedded tissue samples are sliced accordingly

A

they are mounted on glass slides. staining makes it easier to then see under the microscope and identify the cell components

67
Q

what is the most common staining method used in bright field microscopy

A

haemotoxylin and eosin (H&E)

68
Q

give a breakdown on how H&E staining works

A

the haemotoxylin is positively charged and stains basophilic structures, which are negatively charged. these include nuclei, ribosomes, cartilage matrix and the rough endoplasmic reticulum
the eosin is negatively charged and stains eosinophilic structures, which are positively charged, pink. these include collagen, cytoplasmic proteins and mitochondria

69
Q

how does the giemsa stain technique work

A

this is the standard stain for blood and bone marrow smears

70
Q

how does alcian blue stain work

A

this stains acidic polysaccharides blue, like mucin and cartilage

71
Q

what does van gieson stain

A

blood vessels and the skin

72
Q

explain the different staining colours of masson trichrome

A

stains connective tissue blue
stains nuclei dark red or purple
stains cytoplasm, kertain, and erythro red or pink

73
Q

what does masson trichrome stain

A

supporting tissues like collagen

74
Q

what is PAS

A

periodic acid schiff

75
Q
A
76
Q

what is the masson trichrome staining technique used for

A

staining connective tissue - useful for differentiating different types of tissues

Histology (10 decks)

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