EMBEDDING Flashcards
EMBEDDING
• a.k.a.
Casting, Blocking, Molding
• Placing the impregnated tissue into a mold with embedding media, and then allowing the media to solidify
Embedding
: Arrangement of the tissue in a precise position in the mold during embedding
Orientation
• Surface to be cut should be_____ to bottom of the mold
parallel
• Molds should bear the
accession number
3 tyoes of orientation
Embedding
Sectioning
Fish out
Orientation
Tubular tissue:
All layers in transverse sections
Orientation
Skin:
All layers should come (pahigda)
Orientation
Endometrial curetting:
Keep in center
Orientation
Long tissue:
Keep diagonally
Orientation
Intestine:
All layers should come
Orientation
Membrane:
Swiss roll
Cold plate temperature
-20C
TYPE OF MOLDS
Leuckhart’s embedding mold
Compound embedding unit
Plastic embedding rings and base mold
Disposable embedding molds
• It has two (2) L-shaped metal plates, strips of heavy brass metal.
• This is adjustable depending on the size of the tissue.
Leuckhart’s Embedding Mold
• This used for batch embedding thus one of its disadvantages is being prone to the interchanging of samples.
• This is made of interlocking plates and there is a heavy base at the bottom.
Compound Embedding Unit
• In plastic ice trays, we need to grease it first with glycerin/liquid paraffin wax before the process of embedding.
• This is for the ease of separation of the tissue block from the mold after it solidifies.
Disposable Embedding Molds
OTHER EMBEDDING METHODS
Double-embedding method
Plastic resin embedding
• For large blocks of dense tissues; obsolete
DOUBLE-EMBEDDING METHOD
Tissues are first infiltrated with Celloidin and subsequently embedded in a paraffin mass
DOUBLE-EMBEDDING METHOD
• For high resolution light microscopy of thinner than usual sections, renal biopsies, BM biopsies
(1) Epoxy, (2) Polyester, (3) Acrylic Plastic
PLASTIC RESIN EMBEDDING
PLASTIC RESIN EMBEDDING (3)
(1) Epoxy
(2) Polyester
(3) Acrylic Plastic
• For electron microscopy
• Most widely applied, but carcinogenic due to vinylcyclohexane dioxide (VCD) component
EPOXY
Types of epoxy
• Bisphenol A (Araldite)
• Glycerol (Epon)
• Cyclohexene dioxide (Spurr)
Types of epoxy
slow
low viscosity
very low viscosity; fastest
Bisphenol A (Araldite)
Glycerol (Epon)
Cyclohexene dioxide (Spurr)
• For electron microscopy; seldom used
POLYESTER
• For high resolution light microscopy
ACRYLIC PLASTICS
Acrylic plastics
• Examples:
• Plyglycol methacrylate (GMA)
• Methyl methacrylate (MMA)
: catalyst; forms radicals
which are site for polymerization
Benzoyl peroxide
• Acrylic plastics must be stored in ______to prevent radical formation and
premature polymerization
dark bottles
If the embedding medium is too____ for the material, the tissue will not be supported and sections will be torn or shredded.
If the medium is too____ for the tissue, sections will be brittle and will shatter.
soft
hard
To infiltrate the tissues with supporting embedding medium, tissues must be free of all…
water
Paraffin embedded tissues are arranged at the bottom of the mold together with their proper labels and immersed in melted paraffin at a temperature between_____ its melting point and then cooled rapidly in a refrigerator at_____ or immersed in cold water to solidify.
5-10°C above
-5°C
The process by which a tissue is arranged in precise positions in the mold during embedding, on the microtome before cutting, and on the slide before staining, is known as…
Orientation
consists of two 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
Blocks produced are even, with parallel sides, and with a fairly shaped initial setting of the wax.
Leuckhart’s
The mold is adjustable to give a wide variety of sizes to fit the size of the tissue block for casting. It is recommended for routine use, although, too slow and cumbersome for use in a busy laboratory.
Leuckhart’s
is made up of a series of interlocking plates resting on a flat metal base, forming several compartments.
It has the advantage of embedding more specimens at a time, thereby reducing the time needed for blocking.
Compound Embedding Unit
-consist of a special stainless steel base mold fitted with a plastic embedding ring, which later serves as the block holder during cutting.
Plastic Embedding Rings and Base Mold
disposable thin plastic embedding molds, available in 3 different sizes, are simply peeled off one at a time, as soon as the wax has solidified, giving perfect even block without trimming.
It may be placed directly in the chuck or block holder of the microtome.
Peel-Away
-such as those used in ordinary refrigerators may be recommended for busy routine laboratories.
Each compartment may be utilized for embedding one tissue block, which may then be removed by bending the plastic tray once the wax has solidified or by smearing the inner mold with glycerin or liquid paraffin before embedding.
Plastic Ice Trays
are normally utilized for embedding celloidin blocks but are equally useful for paraffin wax blocks.
They have the advantage of being cheap and easy to make.
They provide easy and accurate identification of specimen, thereby avoiding confusion and interchange of tissue blocks.
Rapid embedding of small or large volume of individual specimen is possible, since paper molds can be made to suit any size of tissue.
Paper Boats
used to be recommended for embedding hard tissues such as bones and teeth, and for large sections of whole organs like the eye, since the delicate layers of the eyeball are difficult to keep intact when other media are used
Celloidin or Nitrocellulose Embedding Method
is the process by which tissues are first embedded or fully infiltrated with a supporting medium such as agar or nitrocellulose, then infiltrated a second time with paraffin wax in which they are subsequently embedded.
Double-Embedding
This is used to facilitate cutting of large blocks of dense firm tissues like the brain. They are also recommended for making small sections of celloidin blocks.
Double-Embedding
The introduction of________ media has provided superior results for light microscopic studies, particularly in hard tissues such as undecalcified bone and for high resolution light microscopy of tissue sections thinner than the usual 4-6 µm, such as renal biopsies a n d bone marrow biopsies
plastic resin embedding
Plastics are classified into (3), based on their chemical composition.
epoxy, polyester, or acrylic
Infiltration by______ is slow, partly because the epoxy plastic itself is a large molecule.
Araldite
The ______plastics (____) have a lower viscosity but are often sold as mixtures of isomers.
glycerol-based epoxy (Epon)
_______plastics (____) can be obtained pure, have very low viscosity, and infiltrate fastest.
Cyclohexene dioxide-based (Spurr)
is a Low Viscosity mixture which provides rapid infiltration of tissues. It’s easy to prepare and mixes rapidly.
This resin is compatible with ethanol so no change to propylene oxide is needed prior to infiltration.
Spurr’s Resin
were originally introduced for electron microscopy in the mid- 1950s, but have been superseded by more superior epoxides, and are now seldom used.
Polyester plastics
are made up of esters of acrylic or methacrylic acid, and are used extensively for light microscopy.
Acrylic plastics
Paraffin embedded tissues are arranged at the bottom of the mold together with their proper labels and immersed in melted paraffin at a temperature between_____ above its melting point and then cooled rapidly in a refrigerator at____ or immersed in cold water to solidify
5-10°C
-5°C
available in 3 different sizes, are simply peeled off one at a time, as soon as the wax has solidified, giving perfect even block without trimming. It may be placed directly in the chuck or block holder of the microtome
Peel-Away disposable thin plastic embedding molds
are normally utilized for embedding celloidin blocks but are equally useful for paraffin wax blocks.
They have the advantage of being cheap and easy to make
Paper Boats
They provide easy and accurate identification of specimen, thereby avoiding confusion and interchange of tissue blocks.
Rapid embedding of small or large volume of individual specimen is possible, since it can be made to suit any size of tissue.
Paper Boats
The components of many epoxy plastics are toxic and one of its components,_________ is known to be carcinogenic.
For protection, gloves should always be worn when handling these plastics, and adequate facilities including an operational fume hood must be provided to remove the toxic vapors and properly dispose of toxic waste.
vinyl cyclohexane dioxide (VCD)
were originally introduced for electron microscopy in the mid- 1950s, but have been superseded by more superior epoxides, and are now seldom used.
Polyester plastics
are made up of esters of acrylic or methacrylic acid, and are used extensively for light microscopy
Acrylic plastics
