IMPREGNATION AND EMBEDDING Flashcards
Is the process whereby the clearing agent is completely removed from the tissue and replaced by a medium that will completely fill all the tissue cavities, thereby a firm consistency to the specimen.
IMPREGNATION
Process whereby the impregnated tissue is placed into a precisely arranged position in a mold containing a medium
EMBEDDING, CASTING OR BLOCKING
Is a polycrystalline mixture of solid hydrocarbons
Simplest, most common and best embedding medium
Individual serial sections may be cut with ease
paraffin wax
paraffin wax melting point
39-68 deg celsius
paraffin wax is a rapid process, prepared within ___ hours
24
Tissue blocks and unstained mounted sections maybe stored for ___
indefinite period of time
disadvantage of paraffin wax
Overheated makes tissue brittle
Prolonged will cause excessive tissue shrinkage and hardening
Inadequate impregnation promotes retention of clearing agents, tissues become soft and shrunken, tissue blocks crumble when sectioned and break up when floated in water bath
what are difficult to impregnate and needs long immersion for proper support otherwise they will crumble
bones, teeth, brain, eyes
not recommended for fatty tissues
paraffin
After completely cleared, the tissue is submerged in 2 or more changes of melted paraffin wax either in
oven or incubator at 55 to 60 degree celsius
in modified paraffin waxes, the increase hardness is due to
stearic acid
in modified paraffin waxes, the decrease melting point is due to
phenanthrene
enhance tissue wax adhesion
modified paraffin wax
modified paraffin wax is added with
Added with piccolyte 115, plastic polymers and dimethyl sulphoxide.
Paraffin wax impregnation is the simplest, most common and best embedding medium used for routine processing.
impregnation
Factors Affecting Paraffin Wax Impregnation
- Nature of tissues
- Size of tissues
- Type of clearing agent
Recommended for neurological tissues
Does not require heating during processing; hence, producing minimum shrinkage and tissue distortion especially for cutting large bone tissues
Frozen section technique cannot be done
celloidin impregnation
Made up of series of interlocking plates resting on a flat metal base, forming several compartments.
Compound embedding unit
Consist of a special stainless steel base mold fitted with a plastic embedding ring.
Plastic embedding rings and base mold
Consists of 2 L-shaped strips of heavy brass or metal arranged on a flat metal plate and which can be moved to adjust the size of the mold to the size of the specimen.
Leuckhart’s embedding mold
Cheap and easy to make
Paper boat
Peeled off one at a time, as soon as the wax has solidified
Peel-Away
common wax melting points
45C, 52oC, 56 oC and 58oC.
routine work wax melting point
The 56oC wax is usually used in routine work
Hard tissues require wax with higher _____ than ____ tissues
Hard tissues require wax with higher melting point than soft tissues
3 ways of paraffin impregnation and embedding
By manual processing
By automatic processing
By vacuum embedding
in manual processing, At least ____ changes of waxes are required at ____ minutes interval (for removal of ____)
4; 15; clearing agent
in manual processing, Specimen is immersed into another_______ for___ hours for completely embedding/casting
fresh solution of melted paraffin for 3 hours
Fixes, dehydrates, clears and infiltrates tissues
automatic processing
in automatic processing, only ___ to ___ changes of waxes are required
2 to 3
in automatic processing, there is a constant ____ w/c accelrates and improve tissue penetration
agitation
example of automatic processing
Elliott Bench-Type Processor
The machine is mounted on rollers to permit the turning of platforms and easy access to beakers and wax baths
automatic processing
The presence of odor in the clearing agent during final paraffin wax bath indicates that the paraffin should be ____
changed
most critical stage in automatic processing
Dehydrating agents should be changed regularly since it is the most critical stage
In automatic tissue processing, inadequate dehydration is diificult to correct ____
since tissue is in paraffin
Clearing agents and dilute ethanol should be changed at least ____
once a week
in automatic processing, spillage should be ___.
avoided
fluid and wax container in automatic processing should be filled to the ____ level
appropriate
Wax bath thermostats should be at least ____ above melting point of the wax.
3 degrees
Fastest result
Involves wax impregnation under negative atmospheric pressure inside a embedding oven to hasten removal of air bubbles and clearing agent from the tissue block thereby promoting a more rapid wax impregnation
Removes residual air bubbles in lungs
vacuum embedding
vacuum embedding is used for
For urgent biopsies, brain connective tissue, decal bone eyes spleen CNS
time required is reduced by ___ in vacuum embedding
25-75%
Controlled water jacket usually maintained at _____ above melting point of wax
2 to 4 degree celsius
SUBSTITUTES FOR PARAFFIN WAX
Paraplast
Ester wax
Water soluble media (polyethylene glycols)
are used to investigate heat-and solvent-labile lipids and proteins
polyethylene glycols
Includes agar, gelatine, sodium carboxymethyl cellulose and polyvinyl alcohol
aqueous media
4 main types of mold-embedding
Traditional
Leuckart or dimmock irons or metal containers
Peel-away system using disposable plastic molds
Embedding rings or cassette bases w/c become integral part of the block and serve as the block holder in the microtome.
Most important step in embedding
orienting tissue in the block
Improper placement may result in ____ or ___ tissue portions during microtomy
missed or damaged
Tissues are blocked with the surface to be cut facing ___ in a mold
down
Elongated tissues are placed ______ across the block
diagonally
Tubular and walled specimens such as _____ are embedded en face so as to provide cross sections showing all tissue layers
cyst, fallopian tubes, and GIT
Tissues w/ epithelial surface such as skin are embedded to provide sections in a plane at a ____ angle to the surface
right
Multiple tissue pieces are aligned across the _____ and the center of the mold are not placed ___.
long axis; randomly
