Fixatives

• What type of tissue is described as smooth and loose?


  Smooth, loose tissue
• What methods can hasten the fixation of smooth, loose tissue?


  Heat and agitation
• What is a method of applying heat for tissue fixation?

  Microwave
• What is a method of applying agitation for tissue fixation?

  Vacuum
• What should be done if autopsy materials cannot be fixed immediately?


  Place them in a mortuary refrigerator at 4°C or undergo arterial embalming
• At what temperature should autopsy materials be stored if not fixed immediately?


  4°C
• Why must the brain be fixed before grossing?


  It will not harden because it is too soft if not fixed
• Which hollow organs require cotton soaked in fixative for proper fixation?


  Stomach, gallbladder, intestine
• How should hollow organs be prepared for fixation?


  Insert cotton soaked in fixative, open completely, and soak
• What happens to air-filled lungs during fixation?


  They tend to float with gauze
• How should eyes be prepared for fixation?

  Inject eyes with formol alcohol before submerging with fixative
• What type of fixative is recommended for hard tissue like cervix and nails?


  Perenyi's Fixative
• What are the types of fixatives according to composition?


  • Simple Fixative: 1 component (e.g., Aldehyde)
  • Compound Fixative: 2 or more components
• What are the types of fixatives according to action?

  • Microanatomical: Preserve structural patterns
  • Cytological: Preserve specific cell parts
  • Histochemical: Preserve chemical components
• What are examples of microanatomical fixatives?


  Aldehyde and metallic fixatives
• What is a characteristic of cytological fixatives?


  They preserve specific parts of the cell
• What does glacial acetic acid preserve in cytological fixatives?


  Nuclear chromatin material
• What do cytoplasmic fixatives preserve?


  Cytoplasmic and membrane-bound organelles
• What are the different types of fixatives mentioned?

  Aldehyde, metallic, picric acid, glacial acetic acid, alcohol, osmium tetroxide, TCA, acetone, heat fixation
• What is the common concentration of formalin used as a fixative?


  10% Formalin
• What is the purpose of buffering 10% formalin with phosphorus dioxide?


  To minimize the penetration of formalin pigment
• What is the usual fixative time for 10% formalin?


  12-24 hours
• What are the advantages and disadvantages of formalin as a fixative?


  Advantages:

  • Cheap and readily available
  • Easy to prepare
  • Relatively stable
  • Compatible with many stains

  
  

  Disadvantages:

  • Irritating fumes
  • Skin irritation
  • Prolonged storage leads to p-formaldehyde
• What is the remedy for brown or black crystalline precipitates on blood-containing tissues?


  Removal of formalin pigment using specific methods
• What is 10% formol saline used for?


  Fixation of CNS tissue and general postmortem histochemical examination
• What is the best fixative for routine histopathology?


  10% neutral buffered formalin
• What is the disadvantage of 10% neutral buffered formalin?


  It takes longer to prepare
• What is formal corrosive also known as?

  Formol sublimate
• What is the purpose of alcohol formalin?


  Good for glycogen and microincineration technique
• What is glutaraldehyde composed of?


  Two formalin residues linked by carbon chains
• What is the recommended concentration of glutaraldehyde for small tissue fragments?


  1. 5%
• What is paraformaldehyde used for?


  Thin and ultra-thin sections for plastic embedding
• What is the concentration of mercuric chloride in metallic fixatives?


  1. 7%
• What is the effect of mercuric chloride on tissue?


  It penetrates and hardens tissue rapidly
• What is the purpose of potassium dichromate in chromate fixatives?


  To preserve lipids and mitochondria
• What is the concentration of potassium dichromate used in chromate fixatives?


  3% in aqueous solution
• What does lead fixative preserve?


  Acid mucopolysaccharides
• What is the remedy for the formation of lead carbonate in lead fixatives?


  Add a drop of acetic acid
• What is the use of picric acid fixative?


  Used for glycogen and as a stain
• What is Bouin's fixative used for?


  Embryos and pituitary biopsies