MA1 - Intro to Microanatomy Flashcards
What are the five types of tissue?
blood/lymphoid
muscle
nervous
epithelial
connecive
[mnemonic: Bloody Maries Cause Epithelial Necrosis]
What is the primary function/feature of blood/lymphoid tissue? (2)
transport of gases; immune function
What is the function of muscle tissue? (2)
generates contractile forces that drive internal motion of organ
drives movement of organism itself
What are the three types of muscle tissue?
skeletal muscle
smooth muscle
cardiac muscle
What is the function of nervous tissue?
provides rapid, long-range communication to and from cells/tissues
What are the two types of nervous tissue? (2)
CNS tissue (brain, spinal cord, eye)
PNS tissue (somatic and autonomic nervous systems)
What is epithelial tissue?
sheets of cells (epithelia) that cover internal and external surfaces
Epithelial tissue forms
secretory and ductal elements of glands
What is the function of connective tissue?
supports, insulates, separates, and protects other tissues
The epithelium that forms the innermost tissue layer of intestines is primarily composed of what kind of cells?
absorptive cells (enterocytes) + goblet cells
What is the function of enterocytes in the small intestine?
absorb nutrients
What is the function of enterocytes in the colon?
absorb water
What do goblet cells do?
produce mucus that coats and protects luminal surface
Lamina propria is made of what kind of tissue?
connective tissue
Describe the lamina propria. (2)
contains blood + lymphatic vessels that transport materials to and from epithelium
site of immune reactions
In which cellular structure do immune reactions occur?
lamina propria
List the order of tissue structures, from epithelium at the top to those below.
epithelium
lamina propria
muscularis mucosae
submucosa
muscularis propria
serosa
(mnemonic: ELMo can’t send SMSes)
What structures comprise the mucosa?
epithelium + lamina propria + muscularis mucosae
Describe the muscularis mucosae.
thin layer of smooth muscle
Describe the submucosa.
richer in collagen than lamina propria
The submucosa is responsible for providing support to which structures?
blood vessels
lymphatic vessels
PNS nerves/ganglia that innervate mucosa
Describe the composition of the muscularis propria.
inner circular layer perpendicular to intestinal axis
outer longitudinal layer parallel to intestinal axis
What is the significance of the space between the two layers of the muscularis propria?
ganglia of enteric nervous system reside in space between and control the musclaris propria
Describe the composition of the serosa.
squamous epithelium (mesothelium) that faces peritoneal cavity
thin layer of connective tissue b/w mesothelium and outer smooth muscle layer of the muscularis propria
What are mesothelial cells?
[Alt.] What is the mesothelium?
simple squamous epithelium that lines internal body cavities
lines the serosa
What is the adventitia?
outermost layer of many tubular structures, such as the GI tract
What is the composition of the adventitia? (3)
mostly composed of dense connective tissue
if smooth muscle is present it commonly runs parallel to the tube and serves a support role
lacks mesothelium
What are the steps in histological sample preparation?
sample acquisition
fixation
processing
sectioning
staining
(mnemonic: SFPSS)
What is the purpose of fixation?
to preserve tissue and tissue structure
How is fixation performed?
using chemical fixatives
What are the two types of chemical fixatives used in fixation?
crosslinking fixatives (formaldehyde)
oxidizing fixatives (osmium tetroxide)
What is the difference between immersion and perfusion in fixation?
immersion = sample soaked in fixative - preserves blood cells in vessels
perfusion = fixative introduced into sample through vasculature - blood cells lost
What is the purpose of processing in sample preparation?
replace water with a stiff matrix to facilitate sectioning
What are the two steps of processing in sample preparation?
dehydration
embedding
Describe the dehydration step of processing in sample preparation.
ethanol followed by clearing agent (xylene) to facilitate infiltration by embedding agents
Describe the embedding step of processing in sample preparation. (2)
generates a “block” in which tissue is suspended in solid matrix
waxes such as paraffin or acrylic resins such as methacrylate are used
What happens in sectioning of sample preparation?
block is cut with a microtome = expensive meat slicer
What are the types of stains? (5)
ionic stains
redox stains
fluorescent dyes
heavy metals (EM)
immunostains (IHC, IF, IG)
Basic dyes bind to what charges?
basic dyes (positive charges) bind to negative charges
Acidic dyes bind to what charges?
acidic dyes (negative charges) bind to positive charges
What is the most commonly used stain in histology?
hematoxylin & eosin (H&E)
Describe the components of the H&E dye.
hematoxylin = blue basic dye
eosin = red acidic dye
What happens when H&E staining is carried out under acidic conditions?
hematoxylin binds to macromolecules rich in phosphates (DNA/RNA → thus stains nuclei/ribosomes) and sulfates (proteoglycans)
eosion binds to proteins (which are positively charged), staining them red (therefore stains collagen, actinomyosin, etc.)
Distinguish between the terms basophilic and eosinophilic.
basophilic = stained with hematoxylin → negatively charged area → DNA/RNA/nuclei/ribosomes
eosinophilic = stained with eosin → positively charged area → protein/collagen/actinomyosin
Compare H&E and toluidine blue staining.
Toluidine blue staining has superior contrast
Describe the outcome of toluidine blue staining.
stains nucleic acids and other negatively-charged species blue
stains glycosaminoglycan (i.e. secretory granules of mast cells) reddish-purple
Toluidine blue is commonly used to visualize what specific structure?
mast cells
What is the function of Masson’s trichrome and how does it stain?
used to identify areas of fibrosis
protein-rich areas stained red
collagen stained blue
nuclei stained black
When is Gomori trichrome used?
used to stain skeletal muscle
How does Gomori trichrome stain?
myofilaments of muscle fibers = greenish blue
nuclei = reddish-purple
collagen = green
compacted membranes (i.e. cristae of mitochondria) = red
What stain is used to identify mitochondrial myopathies?
Gomori trichrome
Verhoeff and Gallego stains are used to visualize
elastic fibers
Describe how Verhoeff and Gallego stains visualize fibers.
Verhoeff stains = gives elastic fibers black color but doesn’t stain other structures well
Gallego stains = gives elastic fibers reddish color but stains fibrillar collagens yellow or green
What are the two primary redox stains?
Periodic Acid-Schiff (PAS)
Silver reticulin
Describe the properties of the PAS stain.
reacts with/stains areas rich with polysaccharides
The PAS stain is commonly used to target which cells?
mucus of goblet cells
glycocalyx of enterocytes
external laminae of muscle
basement membrane of epithelia
The PAS stain is used as a diagnostic probe for which kinds of infections?
yeast and fungal infections (since their cell walls have lots of polysaccharides)
Describe the properties of the silver reticulin stain.
redox reaction in which silver ions are reduced to metallic silver by macromolecules
Describe how silver reticulin stains.
stained appears appear black
Silver reticulin is commonly used to visualize
reticular fibers (type III collagen)
Describe how fluorescent dyes are used to visualize structures.
fluorescent dyes fluoresce when excited by specific wavelengths of light
Describe how heavy metals (EM stains) ar used to visualize structures.
heavy metals/EM stains bind to structures and scatter electrons in an electron beam
Describe the role of primary and secondary antibodies in immunostains.
primary antibodies = bind to antigen of interest in the tissue
secondary antibodies = conjugated with enzyme/fluorophore/heavy metal and detect the primary antibody (actually performs the staining)
Describe immunohistochemistry.
uses enzyme-conjugated secondary antibodies (most commonly, horseradish peroxidase)
How does horseradish peroxidase stain?
stains brown where the primary antibody is found
Immunohistochemistry is best used for the visualization of
cells, but not useful for visualizing subcellular structures
Describe immunofluorescence.
uses fluorophore-conjugated secondary antibodies
Immunofluorescence is useful for visualizing
subcellular structures
Describe immunogold.
uses colloidal gold-conjugated secondary antibodies
Immunogold staining is typically combined with what other staining method?
combined with heavy metal stains
Which method is best for visualizing subcellular locations?
immunogold
What are the two types of light microscopes?
transmitted light microscope
fluorescence microscope
What are the two types of electron microscopes?
transmission electron microscope
scanning electron microscope
Describe the properties of transmitted light microscopes.
light is co-linear w/ objective
Describe the properties of fluorescence microscopes.
illuminating light not co-linear w/ objective
stains excited by incident light generate photos (i.e. they fluoresce)
greater specificity than transmitted light microscopy
Which microscopy technique is most commonly used in diagnostic pathology?
transmitted light microscope
Describe the properties of transmission electron microscopes. (3)
TEM generates electron beam that focuses on and passes through sample
beam spread from sample generates magnified image
atoms in sample deflect electrons as function of size of electron shells
How do heavy metals appear in TEM?
heavy metals have large electron shells, so they appear dark on TEM images
Describe the properties of scanning electron microscopes.
SEM uses metal (gold/palladium) plated whole mount samples
electron beam reflects off sample and is imaged at 90° to the beam
rotation of sample allows for generation of 3D image of sample surface
Define scale.
fold difference in size
Define magnification. (2)
ratio of apparent size to true size
is a function of the lens used
Define resolution.
limiting distance at which two discrete objects can be visually distinguished
What factors limit resolution?
resolution limited by wavelength of incident radiation
Write out the formula to calculate resolution. Identify the terms.
d = resolution
lambda = wavelength
NA = numerical aperture
What are the resolution limits for visible light and EM?
visible light = 0.2 um
EM = 1 nm
