Histology Chapter 1

Front 1

What is histology?

Back 1

The study of cells and the extracellular matrix.

Front 2

What are tissues composed of?

Back 2

Interacting components: cells and extracellular matrix.

Front 3

What are the four different types of tissues?

Back 3

Connective, epithelial, muscle and nervous.

Front 4

Compound light microscope: Condenser lens

Back 4

Collects light from illumination source and focuses light on specimen.

No magnification

Front 5

Compound light microscope: objective lens

Back 5

Collects light passing through specimen and forms primary image.

Magnifies primary image (10x, 40x, 100x).

Front 6

Compound light microscope: Ocular lens

Back 6

Enlarges primary image (10x)

Front 7

Magnification

Back 7

Increase in size of object made possible by lenses.

Front 8

Resolution

Back 8

Ability to distinguish two objects as being separate.

Depends on quality of sample and of light.

Front 9

Limit of Resolution

Back 9

Minimal distance separating two objects that still appear separate.

Front 10

Empty Resolution

Back 10

Increase in magnification provides no additional information.

Front 11

Tissue Prep: Fixation

Back 11

Chemical or physical treatment of tissue that preserves natural tissue structure and prevents degradation.

Goal: to mimic normal morphology.

Front 12

Four properties of fixatives

Back 12

1. Penetrate rapidly to prevent postmortem changes.

2. Coagulate cell contents into insoluble substances.

3. Protect tissue against swelling and shrinkage.

4. Allow cell parts to selectively take up dyes.

Front 13

Common Fixatives

Back 13

Single chemicals do not have all properties of fixatives.

Common fixatives must use combinations for best results.

Front 14

Make up of Bouin's Fixative

Back 14

Formaldehyde (75mL), picric acid (25mL), acetic acid (5mL)

Front 15

Purpose of formaldehyde in bouin's fixative

Back 15

Fixes cytoplasm but not nucleus.

Retards paraffin penetration.

Front 16

Purpose of picric acid in Bouin's Fixative

Back 16

Coagulates cytoplasm to aid paraffin entry.

Fixes chromatin

Shrinks the tissue

Front 17

Purpose of acetic acid in Bouin's Fixative

Back 17

Compensates for defects of formaldehyde and picric acid.

Front 18

Common Fixative: Formalin

Back 18

37% formaldehyde

Cheap and effective

Interacts with proteins but not lipids

Front 19

Properties of fixatives

Back 19

Typically aqueous solutions.

Harden tissue but not enough for sectioning.

Must replace water with something that allows for sectioning: paraffin or plastic.

Front 20

Why must dehydration follow fixing?

Back 20

water is incompatible with paraffin or plastic.

must remove water with graded series of alcohol washes to 100%

Front 21

What is clearing?

Back 21

Replacement of alcohol (from dehydration) with something miscible with paraffin.

Liquid hydrocarbons: toluene and xylene.

Front 22

What steps are involved in embedding?

Back 22

Warm tissue and organic solvent.

Add chips of paraffin to warm solution to dissolve paraffin.

Continue adding more paraffin then transfer tissue to 100% soluble paraffin,

Allow wax to harden.

Front 23

What is used to section?

Back 23

Microtome cuts tissue into 5-7 µm.

Front 24

Why are stains aquous?

Back 24

They are incompatible with wax,

Front 25

How do you stain tissue?

Back 25

Remove parafffin by transferring slides into xylene, then pass slides through graded series of increasing concentrations of water.

Immerse in stain.

Front 26

What are the three general types of stains?

Back 26

1. Differentiate between acidic and basic.

2. Specialized for fibrous parts of ECM.

3. Metallic salts ttat precipitate on tissues.

Front 27

H&E

Back 27

Hematoxylin and Eosin stain.

Hematoxylin: aqueous base that colors acidic components bluish or purplish--RNA and DNA.

Eosin: alcoholic acid that colors basic components pinkish--proteins.

Front 28

Basophilic

Back 28

Something that is acidic and is stained by a basic dye.

Front 29

Acidophilic

Back 29

Something that is basic and is stained by an acidic dye.

Front 30

Histochemistry

Back 30

science of using chemical reactions between laboratory chemicals and components within tissue.

Front 31

Cytochemistry

Back 31

biochemistry of cells, especially that of the macromolecules responsible for cell structure and function

Front 32

Immunochemistry

Back 32

process of detecting antigens (e.g., proteins) in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues.

Front 33

Fluorescence (immunofluoresence)

Back 33

when certain substances are irradiated by light of a certain wavelength, they emit light with a longer wavelength.

Front 34

Autoradiography

Back 34

• Method of localizing newly synthesized macromolecules (DNA, RNA, protein, glycoproteins and polysaccharides) in cells or tissue sections.

Front 35

Viewing living cells: phase contrast

Back 35

is an optical microscopy illumination technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image.

Front 36

Viewing living cells: differential interference

Back 36

also known as Nomarski Interference Contrast (NIC) or Nomarski microscopy, is an optical microscopy illumination technique used to enhance the contrast in unstained, transparent samples.

Front 37

Viewing living cells: dark field

Back 37

describes microscopy methods, in both light and electron microscopy, which exclude the unscattered beam from the image. As a result, the field around the specimen (i.e. where there is no specimen to scatter the beam) is generally dark.

Front 38

Electron microscopy

Back 38

uses a beam of electrons to illuminate the specimen and produce a magnified image.

Front 39

Fixation

Back 39

pieces of organs are promptly and adequately treated after being removed from an animal’s body to avoid tissue digestion via autolysis or bacteria and to preserve molecular composition.

Front 40

Fixatives

Back 40

solutions of stabilizing or cross-linking agents used in chemical fixaition.

Front 41

Formalin

Back 41

buffered isotonic solution of 37% formaldehyde; best fixative for light microscopy.

Front 42

Osmium tetroxide

Back 42

used to preserve and stain lipids and proteins. Useful for high resolution (electron) microscopy.

Front 43

Dehydration

Back 43

step 1 of paraffin embedding. Water is extracted from fragments to be embedded by bathing them successively in a graded series of mixtures of ethanol and water (70%-100% ethanol)

Front 44

Clearing

Back 44

step 2 of paraffin embedding. Ethanol (from dehydration) is replaced with a solvent miscible with both alcohol and the embedding medium. As tissues are infiltrated with this solvent, they generally become transparent.

Front 45

Microtome

Back 45

instrument used for sectioning paraffin-embedded tissue for light microscopy.

Front 46

Cryostat

Back 46

freezing microtome. Physically freezes tissue samples, making them hard and ready to be sectioned.

Front 47

Basophilic

Back 47

tissue components with negative charge (anionic) that stain more readily with basic dyes.

Front 48

Acidophilic

Back 48

cationic components (proteins with many ionized amino groups) have affinity for acidic dyes.

Front 49

Hematoxylin and eosin (H&E)

Back 49

most common combination of dyes.

Hematoxylin stains DNA of cell nucleus and other acidic structures (RNA-rich portions of cytoplasm and matrix of cartilage) blue.

Eosin, in contrast, stains other cytoplasmic components and collagen pink.

Front 50

Trichromes

Back 50

e.g. Mallory stain, Masson stain, show nuclei and cytoplasm. Help to distinguish extracellular tissue components better than H&E.

Front 51

Cell line

Back 51

many types of cells, once isolated from normal or pathological tissue, have been maintained in vitro because they have been immortalized and now constitute a permanent cell line.

Front 52

Hybridization

Back 52

binding between two single strands of nucleic acids (DNA with DNA, RNA with RNA or RNA with DNA) that recognize each other if the strands are complimentary.

Front 53

in situ hybridization (ISH)

Back 53

hybridization occurs when solution of nucleic acid is applied directly to cells and tissue sections.

Front 54

Serial sections

Back 54

parallel sections

Front 55

Freeze fracture

Back 55

a preparation method useful for examining lipid membranes and their incorporated proteins in "face on" view.

Front 56

Cryofracture

Back 56

a procedure for preparing cells or other biologic samples for electron microscopy in which the sample is frozen quickly and then broken with a sharp blow.

Front 57

freeze etched

Back 57

A method of specimen preparation for electron microscopy in which a replica is made from a sample that has been rapidly frozen and then fractured along natural planes of weakness to reveal its internal structure.

Front 58

primary culture of cells

Back 58

Once isolated, cells can be cultivated in clear dish, to which they adhere, usually as single layer of cells.

Front 59

Birefringence

Back 59

ability to rotate the direction of vibration of polarized light.

Feature of crystalline substances or substances containing highly oriented molecules, such as cellulose, collagen, microtubules and microfilaments.

Front 60

Normanski differential interference microscopy

Back 60

produces an image with a more apparent three-dimensional aspect than in routine phase-contrast microscopy.

Front 61

Phase-contrast microscorpy

Back 61

uses a lens system that produces visible images from transparent objects.

Front 62

Resolving power

Back 62

smallest distance between two particles at which they can be seen as separate objects. Max resolving power in light microscopes is 0.2µm.

Front 63

Bright-field microscope

Back 63

stained preparations are examined by means of ordinary light that passes through the specimen.

Front 64

Metal impregnation techniques

Back 64

usually use silver salts as common method of visualizing certain ECM fibers and specific cellular elements in nervous tissue.

Front 65

Lipid-soluble dyes

Back 65

used to reveal lipid-rich structures.

Front 66

Counterstain

Back 66

usually a single stain that is applied to a section by another method to allow better recognition of nuclei or other structures.

Front 67

Enzyme digestion

Back 67

pretreatment of a tissue section with an enzyme that specifically digests one substrate, leaving other adjacent sections untreated.

Front 68

Proteoglycans

Back 68

proteins that are heavily glycosylated—core protein with one or more GAG chains.

Front 69

Glycosaminoglycans (GAGs)

Back 69

anionic, unbranched long-chain polysaccharides containing aminated sugars.

Front 70

Periodic acid and Schiff reagent (PAS)

Back 70

used in Fuelgen reaction to identify and quantify DNA by hydrolysis of deoxyribose.

Front 71

Glycogen

Back 71

ubiquitous free polysaccharide in animal cells. Can be demonstrated by PAS in liver, striated muscle and other tissues where it accumulates.

Front 72

Oligosaccharides

Back 72

short branched chains of sugars. Chains of these called glycans.

Front 73

Glycoproteins

Back 73

proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide side-chains.