CHAPTER 1 Pt. 1 Histology and Its Methods of Study Flashcards
The study of tissues of the body and how these tissues are arranged to constitute organs
Histology
Tissue’s 2 interacting components
cell; extracellular matrix
ECM two components
fibers; ground substance
supports the cells and contains the fluid transporting nutrients to the cells, and carrying away their wastes and secretory products
ECM
produce the ECM locally and are in turn strongly influenced by matrix molecules
Cells
many of the matrix components bind to _________________that span the cell membranes and connect
to structural components inside the cells, forming a continuum in which cells and the ECM function together in a well-coordinated manner.
specific cell receptors
become functionally specialized and give rise to fundamental types of tissues with characteristic structural features.
cells and their associated matrix
formed by an orderly combination of these tissues,
and their precise arrangement allows the functioning of each
organ and of the organism as a whole
Organs
The most common procedure used in histologic research
preparation of tissue slices or “sections”
most common microscope
bright field
The ideal microscopic preparation is preserved so that the
tissue on the slide has the same structural features it had in the
body. However, this is often not feasible because the preparation process can remove ___________, with slight distortions
of cell structure.
cellular lipid
Basic Steps used in tissue preparation for light microscopy (Fix, De, Cle, In, Em, Tri)
Fixation
Dehydration
Clearing
Infiltration
Embedding
Trimming
most critical step in tissue processing
Fixation
aka preservation
Fixation
To preserve tissue structure and prevent degradation by
enzymes released from the cells or microorganisms, pieces of organs are placed as soon as possible after removal from the
body in solutions of stabilizing or cross-linking compounds
called __________
fixatives
fixatives are often
introduced via blood vessels, with vascular perfusion allowing
fixation rapidly throughout the tissues to
improve ________________ in large organs
cell preservation
widely used fixative for light microscopy
Formalin
how does formalin form?
Formaldehyde is dissolved in water forming 37% formaldehyde buffered isotonic solution
fixative used for electron microscopy
formalin and glutaraldehyde
formalin and glutaraldehyde react with _________ groups of proteins preventing their degradation by common proteases
amine (NH2)
also cross-links adjacent proteins, reinforcing cell and
ECM structures.
Glutaraldehyde
provides much greater magnification and resolution of very small cellular structures,
and fixation must be done very carefully to preserve additional “ultrastructural” detail.
electron microscopy
For “ultrastructural” detail, glutaraldehyde-treated tissue is then immersed in
buffered
osmium tetroxide
preserves (and stains) cellular lipids as well as proteins.
osmium tetroxide
Embedding materials include ________, used routinely for light
microscopy, and __________, which are adapted for both
light and electron microscopy.
paraffin; plastic resins
having its water extracted gradually
dehydration
reagent for dehydration
ethanol
alternative reagent for dehydration
Isopropanol
clearing is aka
dealcoholization
The ethanol is then replaced by an
organic solvent miscible with both alcohol and the embedding
medium; infiltration with
the reagents used here gives the tissue a translucent appearance.
clearing
reagent for Clearing
cylin (cylon)
alternative reagent for clearing
toluene
The fully cleared tissue is then placed in melted paraffin
in an oven at 52°-60°C, which evaporates the clearing solvent
and promotes ________ of the tissue with _______
inflitration; paraffin
paraffin _________spaces in tissue
infiltrates
the infiltrated tissue is buried in
paraffin wax
embedded by allowing it to harden in a small container of
paraffin at ___________.
room temperature
Tissues to be embedded with
_________ are also dehydrated in ethanol and then infiltrated
with plastic solvents that harden when cross-linking polymerizers are added
plastic resin
avoids the higher temperatures needed with paraffin, which helps avoid tissue distortion.
Plastic embedding
The hardened block with tissue and surrounding embedding medium is trimmed and placed for sectioning in an
instrument called a
a microtome
Paraffin sections are typically cut at ______ thickness for light microscopy
3-10 μm
electron microscopy requires sections less than _____ thick
1 μm
A microtome called a ________in a cabinet at subfreezing temperature is used to section the block
with tissue, and the frozen sections are placed on slides for
rapid staining and microscopic examination by a pathologist.
cryostat
embedding aka
casting/blocking
microtome aka
rotary/minot
Cell components with a net negative charge (anionic), have an affinity for
basic dyes
have an affinity for
basic dyes and are termed
basophilic
Cell components with cationic components,
such as proteins with many ionized amino groups, stain more
readily with
acidic dyes
proteins with many ionized amino groups, stain more
readily with acidic dyes and are termed ___________.
acidophilic
Examples of basic dyes include
toluidine blue
alcian blue
methylene blue.
a dye that has net + charge attracting substances that are negatively charged
basic dye
a dye that has net - charge repelling a negatively charged substances
acidic dye
simple combination of staining methods
hematoxylin and eosin (H&E)
Hematoxylin stains:
- DNA in the cell nucleus
- RNA-rich portions of the cytoplasm
- matrix of cartilage
Eosin is considered a ____
counterstain - to distinguish additional features of a tissue
utilizes the
hexose rings of polysaccharides and other carbohydrate-rich
tissue structures and stains such macromolecules distinctly
purple or magenta
periodic acid–Schiff (PAS) reaction
The
DNA of cell nuclei can be specifically stained using a modification of the PAS procedure called the
Feulgen reaction.
Lipid-rich structures of cells are revealed by avoiding the processing steps that remove lipids, such as treatment with
heat and organic solvents, and staining with lipid-soluble dyes such as _____
Sudan black
typically using solutions of silver salts to visual certain
ECM fibers and specific cellular elements in nervous tissue.
metal impregnation techniques
