Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biomedical techniques BMI3702 > Histopathology > Flashcards

Histopathology Flashcards

1
Q

Grossing

A

process whereby pathology specimens are inspected with the naked eye to obtain diagnostic info

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Points to note before tissue processing for microscopic examination

A
  • Identification of the specimen- confirmation of patient and anatomical site from which specimen was obtained
  • clinical details
  • gross description-written record of the physical appearance of the specimen
  • only a small portion from a large specimen can be -subjected to microscopic examination hence during grossing a skilled person should do the examination
  • only soft tissue can be cut into small blocks and processed directly
  • bony specimen need to be decalcifies prior to processing
  • bones and teeth require special treatment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Items that should be in a gross room

A
  • cutting board fluid from board must run directly into a sink
  • shelves for specimen containers
  • ready access to hot and cold water
  • ready access to formalin
  • box 0f instruments containing forceps of various sizes, scissors of various types and sizes, a probe, a bone cutting saw or electric bone cutter, scalpel handle, disposable blades, long knife, ruler to measure size of lesions and specimens
  • box with cassettes and labels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Lab hazards and safety measures

A

-formalin vapours are irritants affecting the eyes and throat. Exhaust may be used as outlet for vapours
-always use a mask, apron, aye glasses and gloves as protection from:
infected material
formalin vapours
spilt blood or any other fluid
-keep grossing table clean with antiseptic solution
-all specimen should be in a container with 10% formalin and covered with a lid
-after grossing specimens should be kept according to accession numbers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Histopathology lab

A

should be large enough to accomodate various types of equipment and must allow personnel to work with ease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Equipment kept in a histopathology lab

A 
tissue processor
tissue embedding table
microtome
tissue warming table
tissue flotation bath
slide stainer or glassware for manual staining
table to label and dispatch the slides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Handling of specimen

A

specimen should be transported in a glass, plastic or metal container or in a plastic bag in 10% formalin. If formalin is not avail, place specimen in refrigerator at 4 degrees to slow autolysis. Container should have opening large enough so tissue can be removed after hardening by fixation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Fresh ,material is needed for

A 
frozen section
immunocytochemistry
cytological examination
microbiological sampling before histology
chromosome analysis
research purposes
museum display
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Principles of gross examination

A

proper identification and orientation of specimen
unlabelled specimen should never be processed
properly completed histopathology requisition form should contain patients name, sex, age, relevant clinical data, surgical findings, nature of operation and type of tissue submitted
careful search and examination of all the tissue in the order in which it was submitted
surgeon should be instructed to submit all the material he/she removed rather than selecting a portion from it
specimen should be placed on the cutting board in the correct anatomical position before recording type of specimen structure dimensions weight shape colour consistency surgical margin
measurements are usually given in cm unless specimen is very small in which mm can be used
endometrial and prostatic tissue should be measured by aggregate pieces in volume
endoscopic biopsies should be numbered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Sampling for histopathological examination

A

tissue submitted must not be more than 3mm thick and not larger than the diameter of the slides used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Histological technique

A

deals with preparation of tissue for microscopic examination. Aim is to preserve the microscopic anatomy of tissue and harden it so that a very thin section can be made.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Processes for the histological technique

A 
fixation
dehydration
cleaning
embedding
cutting 
staining
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Fixation

A

carried out as soon as possible after tissue removal to prevent autolysis. purpose is to preserve tissue constituents so they will withstand treatments with various reagents with min loss of architecture
expose tissue to chemical compounds called fixatives

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Mechanism of action of fixatives

A

denature or precipitate proteins which then form a sponge or meshwork that tends to hold other constituents
important factors: fresh tissue, proper penetration of tissue by fixatives
correct choice of fixatives
no fixative will penetrate piece of tissue thicker than 1cm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How to deal with tissue thicker tan 1cm for fixation

A

solid organ: cut slices no thicker than 5mm
Hollow organ: either open or fill with fixative or pack lightly with wool soaked in fixative
large specimen which require dissection: inject fixative along vessels so that it reaches all parts of the organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Properties of an ideal fixative

A

prevents autolysis and bacterial decomposition
preserves tissues in its natural state and fixes all components
makes cellular components insoluble to the reagent used in tissue processing
preserved tissue volume
avoids excessive hardness of tissue
allows enhanced staining of tissue
should be non-toxic non-allergic for user
should not be very expensive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Fixation temperature

A

can be carried out at room temp
tissue should not be frozen once it has been placed in fixative solution for a peculiar ice crystal distortion will result

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Speed of fixation

A

almost 1mm/hour therefore fixation time of several hours is needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Amount of fixation fluid

A

10-20 times volume of specimen

fixative should surround specimen on all side

20
Q

Factors affecting fixation

A

size and thickness of piece of tissue
tissue covered by large amount of mucus’s fix slowly as does tissue covered by blood or organs containing very large quantities of blood
fatty and lipomatous tissue fixes slowly
fixation is accelerated by agitation and maintaining a temp of 60 degrees

21
Q

Classification of fixatives

A 
Tissue fixatives
-buffered formalin
-buffered glutaraldehyde
-zenkers formal saline
- Bowen's fluid
Cytological fixatives
-ethanol
-methanol
-ether
Histochemical fixatives
-formal saline
-cold acetone-absolute alcohol
22
Q

Routine formalin

A

Formalin is sold as 40% w/w solution of formaldehyde gas in water. It is used as 10% solution in water or normal saline. It does not precipitate protein but combined with the NH2 group to form an insoluble gel it preserves all elements including fats. It keeps phospholipids insoluble in fat solvents. Tissue can remain in it for prolonged periods without distortion. Compatible most special stains it is the cheapest and most popular fixative

23
Q

Ethyl alcohol

A

used at 90-100% strength. It precipitates albumin but not nucleoprotein. It causes shrinkage and hardening of tissues and destroys mitochondrion. It preserves glycogen and is useful for the histochemistry of glycogen, uric acid and iron.

24
Q

Tissue processing

A

process of getting tissue into paraffin wax
24 hours manually or mechanically
To cut thin sections of a piece of tissue it should have suitable hardness and consistency when presented to the knife edge. These properties can be imparted b y infiltrating and surrounding the tissue with paraffin wax, colloidin or low-viscocity nitrocellulose, various types of resins or by freezing.

25
Q

Tissue processing is divided into

A 
dehydration
cleaning
embedding
impregnanting
specimen should be labelled first
shouldn't use a pen with ordinary ink, printed graphite pencil, written, typewritten or India ink-written labels
26
Q

Transporting tissue through various steps of processing

A

the cut specimen are put in myelin cloth together with their labels and then transported from reagent to reagent in metal containers with perforated walls so reagent enters the tissue

27
Q

Manual tissue processing

A

tissue is moved from one container of reagent to another by hand

28
Q

Mechanical tissue processing

A

automatic tissue processors contain diff jars with reagents. These are arranged in a sequence. The tissue is moved from one jar to another by a mechanical device. Timings are controlled by a timer which can be adjusted to measure hours and or minutes. The temp is maintained at 60 degreed

29
Q

Dehydration

A

water in tissue ir replaced by alcohol
tissue are dehydrated using strong alcohol e.g. 50% 70% 90% 100%
duration tissue are kept in each strength of alcohol depends on size of tissue, fixative used and the type of tissue. Delicate tissue will undergo a high degree of shrinkage in too great a concentration of alcohol therefore will start slowly at a lower % of alcohol
Volume of alcohol should be 50-100 times that of the tissue

30
Q

Clearing

A

Alcohol is replaced by paraffin wax.
Parrafin is not alcohol soluble the alcohol must be replaced with a substance in which wax is soluble this step is called clearing

31
Q

Tissue clearing is achieved by using any of these reagents

A 
xylene ( commonly used small pieces of tissue are cleared in 0.5-1 hour while larger pieces in 2-4 hours)
chloroform
benzene
carbon tetrachloride
toluene
32
Q

Impregnation with wax

A

occurs at melting point of paraffin wax which is at 54-60 degrees
Volume of wax should be about 25030 times the volume of tissue. Duration of impregnation depends on size and type of tissue and the clearing agents employed. Longer periods required for larger pieces and harder tissues like bone and skin. Using xylene is the easiest way to remove wax. IN total 4 hours is sufficient

33
Q

Types of wax employed for impregnation

A

paraffin wax
water-soluble wax
other material like colloidin, gelatin, paraplast

34
Q

Blocking aka ambedding

A

impregnated tissues are placed in a mould with their labels and then freshly melted wax is poured into the mould and allowed to settle and solidify. Once block has cooled sufficiently to form a surface skin it should be immersed in cold water to cool it rapidly. After the block has completely cooled down, it should be cut into individual blocks after which each must be trimmed. Labels must be made to adhere on the surface of the block by melting the wax with a metal strip which has been sufficiently warmed

35
Q

Staining

A

process by which colour is given to a section

36
Q

Classification of stains

A

Acid stain
Basic Stain
Neutral stain

37
Q

Dye

A

all dye are composed of acid and base components

Dye is a compound which can colour fibres and tissue constituents

38
Q

Acid dyes

A

basic component is coloured while the acid component is colourless. Acid dyes stain basic components. Colour imparted is a shade of red

39
Q

Basic dyes

A

acid component colourless. Basic dyes stain acidic componets. Colour imparted in shade of blue

40
Q

Neutral dyes

A

acid dye combined with basic dye
as it contains both coloured radicals, it gives different colours to each of the cytoplasm and nucleus. This is the basis of Leishman stain

41
Q

Staining procedure

A

staining can be done manually or mechanically ( automatic )
Manual staining: method of choice in a small lab, few slides stained daily
time consuming and economical
diff reagents containers are placed in a special sequence and the slides are moved manually from one container to another

Automatic staining: in a busy histopathology lab where hundreds of slides are stained daily
uses diff containers of staining reagents arranged according to the desired sequence, Has a timer which controls period for which slides should remain in given container, A mechanical device shifts the slides from one container to the next after a specified period

42
Q

Advantage of automated stainer

A

reduces manpower
accurately controls timing of staining
large number of slides can be stained simultaneously
lower quantities of reagents used

43
Q

Haemotoxylin ( basic dye) and Eosin staining ( acid dye)

A

the most commonly used routine stains in any histopathology lab

44
Q

Frozen sectioning

A

freezing makes tissue solid enough to section with microtome
tissue is frozen rapidly at -20 degreed and sections are cut and stained. In this way tissue can be examined microscopically within 5-10 min of its removal from the body. It reduces time of processing from 18 hours to five minutes. It has the disadvantage that only 8-16 micron thick sections can be cut and finer details of tissue cannot be examined. Performed on a machine called cryostat

45
Q

Frozen sections helpful for

A

when rapid diagnosis regarding benign or malignant nature of a lesion is required to decide the extent of surgery while the patient is still on the operating table
when a study of fat proteins or antigenic markers is required as the routine processing of tissue destroys them

Biomedical techniques BMI3702 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions