Histology Lecture #1 Flashcards

1
Q

Histomorphology

A

Histo = Tissue

Morphology = Structure

Histomorphology = looking at the structure of tissues
- This is what we see on microscope slides

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2
Q

Why is Histology hard to understand?

A
  1. Unfamiliarity with tissue structures and microscopicpictures of them
  2. 2D to 3D view of an object - get a 2D slices form 3D object and you need to translate 2D to 3D
  3. Problems of Scale (You want to knw the magnification of an image or know if it is zoomed in and without that information it is hard to tell what the image is)
  4. Complexity
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3
Q

Making Histology Slides

A

Take sample –> Formalin fix using FFPE –> then remove all the aqueous components using ethonol –> then then embed in wax –> then slice the block

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4
Q

Formalin fixation

A

Emerge the sample in formadheyhe
- This cross links and stabilizes the tissue allow you to cut it

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5
Q

Thickness of histology slide

A

4-5 micrometers thick (thinner than seran wrap and the thickness of 2 bacteria)

Being so thin allows you to put the slice on a slide

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6
Q

Why do you stain

A

Because the slice is so thin without the stain you can’t see anything - color allows you to see better

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7
Q

Most common Stain

A

Homotoxin and Eosin (H and E; H/E)

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8
Q

Example of unfamiliarity with structures

A

Skin - the skin has different components but looking a slide means it is hard to know what it looks like in 3D unless you know the structure of skin
- If you know 3D then you can make sense of the shape of the structire

Image - can see that if you know the 3D structure then teh 2D stucture because eaiser to understand

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9
Q

2D to 3D issue

A

When looking at a slide you have a 3D structure that has a shape
- What you see on the slde depends on the cutting plane (Depending on how it is cut affects the shape hat you get)

Example – see different cuts in cone you get different shapes

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10
Q

Slice fruit exmaple

A

Shows that depending how how you cut (the plane that you cut in) you will get a different shape/different pattern

ALSO depending on the location that you cut you will get a different image
- Example - different place you cut on orange = get different shape

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11
Q

Tube-like structures in Histology

A

Many tissues have tube-like structures (Example - have nerves, ducts, and Blood vessels)
- These tubes will live around in 3D space (bend or folds) or can branch

Issue = depending on the cutting plane you can get different images + depending on where you cut you get a different shape/image –> get different shape = don’t know what your looking at

Example image - Circle cut out of bend - if i image the circle is made of cells = this would be circle of cells and you might think its a sphere shape

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12
Q

White space in histology

A

Often the center of a structure (tube or a duct) - shows an opening
- Means that there was something there that had contents (Ducts or storage structure)

Example in image - see white is a duct and that the duct branches

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13
Q

Issue of complexity

A

In a textbook you often have a clear cartoon image that is simplified to be less confusing BUT on a slide it is not a simplified cartoon (more complicated)

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14
Q

Issue of problem with scale

A

In images they often do not tell you the scale = don’t know the magnification or if the image is zoomed in
- You might assume they are all the same magnification and this makes it harder to understand the image

Example - When looking at a map - when all the way zoomed out you can’t see houses -> then zoom in and see a bunch of houses –> then zoom in on one house and see the car in the driveway

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15
Q

Example of Scale issue

A

Image is of a Kidney –> can see the ducts
- White = interior of ducts

When zoom in = can see things that you didn’t see before (now can see the cells and more ducts)

THEN zoom more on the Glomerulus - now see things that you didn’t see before (see fine details)

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16
Q

Solutions to Issues

A
  1. Gain familiarity
  2. Learn to recognize common elements
  3. Keep the 3rd dimension in mind
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17
Q

Common elements in histology

A
  1. RBCs (very pik/organy red)
  2. Nucelri/nuc shapes
  3. White spaces
  4. Form follows function
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18
Q

Form follows function examples

A

Top Image - Lungs - oxygenates blood = need many blood vessels + many air spaces = see lots of open space + Lots of RBCs + Lots of capillaries
- See blodd vessels and air

Bottom Image - Kidney - filters blood –> had many blood vessels = in image should see manu blood vessels and ducts
- See many ducts for blood filtration

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19
Q

Using Landmarks

A

Can use landmarks to determine scale

Example 0 Use RBCs (Fairly uniform - 7 microns) –> if see RBCs in tissue = know the scale + RBCs can give you a sense of what organ you are in
- Know size of RBCs = can know the size of other things (Ex. know the size of nuclei are similar because see that they are similar in size to RBCs)

20
Q

Histology

A

The study of the microscopic structure of tissues and ____
- Looks at morphology of cells
- Used for diagnosis of diseases (infections + cancer etc.)

21
Q

What is often used in histology?

A

Histology is enhanced using stains –> stains brings out part of the tissue to make it more visible

22
Q

Types of stains

A
  1. H and E
  2. Special stains (Trichrome, PAS, Gram)
  3. Imunohistchemistry (IHC)
23
Q

How do we make a slide

A
  1. Place tissue (peice or whole organ) in forlmalin
  2. Trim the tissue and place in cassetes
    • Indictae to technition what tissues are on the slide + often place it in how you want them cut (shows how to orient them)
  3. Process the Tissue - Remove the formaline and replace with enthnol to remove the water
  4. Embed in parafin - ethonol in the tisue is replaced with wax
  5. Section and place on slide - cuts 5-10 microns (thin enough to be translucent)
  6. Stain slide
24
Q

Purpose of Formalin

A

Preserves the tissue - Kills microbes and stops enzymatic activity (Prevents aitosis)

  1. Prolonged fixation - cross-links the proteins
    • This could INTERFERE with IGC = don’t leave it for too long if doing IHC
25
Q

What does ethonol do in slide preperation

A

Removes the water - when you replace formalin with ethonol the water is removed
- Need to remove the water for parafin infiltration

26
Q

Why embed in Parafin

A

The parafin provides a stable medium that allows you to section the tissue and store the tissue for long periods of time

27
Q

Why stain slide

A

Done to visualize the tumor/microbe/cell/protein/nucelic acid of interest
- H/E = can see cells and nucelus
- IHC = can see proteins + nucelc acids

28
Q

Hematoxylin and Eosin

A

Hemotaxalin is a blue/purple dye - blue parts = nucleus, RNA-rich parts of the crtoplams + hyaline cartalige matrrix (colors the basophilic structures)
- Basophilic stains purple because of chromatin

Eosin is a pink/red stain - stains the cytoplasm and collogen (Stains eosinphilic parts)

***H/E is hydrophilic and will not stain hydrophobic cells (lipids and fats)

29
Q

What affects the color of H and E staining

A

Color is different depending on how the stain is appplied + how long it is applied for

30
Q

Example H and E Staining

A

Left image - arrow points to capsid (Satined with eosin)

Bottom right - Nucleus stains purple; cytoplasm stains pink

31
Q

Peiodic Acid-Schiff (PAS)

A

Overall: Reaction involved the oxidation of 1,2 glyceral groups of vicinal diols to oxidize to aldehydes
- Schiff reagent reacts with oxidized glycerols to produce deposits of aldeamines

Used to stain glycogens (polysaccrides) + glycoproteins + Basement membranes

32
Q

When do you use PAS

A

Use if have a disease that affects basement membranes (because it stains basement membranes) + used for glycogen storgae disorders

33
Q

PAS example

A

Staining of basement membrane - doesnt stain the surrounding ___ + see bowman’s capsule in dark purple

*CHECK SLIDE 21

34
Q

Type of cells that are PAS positive

A

Globlet cells are PAS positive
- Goblet cells = line the intestine + produce muscus
- Goblet cells = basophilic color = shows PAS positive

35
Q

Masson’s Trichrome (TRI)

A

Overall: Uses 3 dyes for different structires

Distictive feature = stans collegen blue
- Stains nuclei brown + cytoplasm red
- Distiguishes cells from extracellular compenents –> allows the pathologst to asses for fibrosis (scarring) of tissues

Use - used t asses fibrosis

36
Q

Dyes used in TRI

A
  1. Iron hematoxylin
  2. Biebrich scarlet
  3. Anilline Blue
37
Q

Example TRI #1

A

Shows fibrosis in Macaque heart - seen by the adundant abount of collegen (see collegen in the blue fibers)
- Stain difefrentiates collegen fibers

38
Q

Example TRI #2

A

Shows collegen fibers in the dermins (shows the collegen stains blue)
- Other cells stain other colors

39
Q

Verhoef-Van Gieson (VVG)

A

Overall: Iron hematoxylin interacts with elastic fibers (Elastin) – stains elastin black
- Stains collogen red
- Other structires stain yellow

Use - identifies elastic fibers/bands (Especially within blood vessels)

40
Q

Example VVG

A

Shows difference for artiers and veins
- Dfference between artery and vein has to do with the number of elastin fibers = looking at amount alllows you to differentate between the two

Image = can see elastic lamina stains black in artery

41
Q

Epithelium Definition

A

One or more layers of cells that together form a barrier betweeen two different envirnments

Location - Lining the outter surface (skin) andinnercavities of the body (ex. lungs + GU tract + reproductive and urinary tract + blood/lymph circulatory systems)

Function = Secretion + absorbtion _+ protection + transprotaion + Sensation

42
Q

Types of Epithelium

A
43
Q

Epithelium Example 1 (blood vessels)

A

Epithelium lining BV = endothelium
- Type = Simple squamous epithelium

Function = transport + clotting/homeostasis + inflamation + blood pressure control

44
Q

Epithelium Example 2 (GI tract)

A

Slide 34 ____ Epithelium lines lumen of the GI tract
- can see goblet cells = PAS positive
- Type = Simple columnar epithelium

Function - Absorptive cells take in nutrients + goblet cells secrete mucus

45
Q

Connective Tissue

A