Introduction to Histology Flashcards
What are the 4 main tissue types?
Epithelial, connective, muscle and nervous tissue
What is histology?
the microscopic study of normal cells and tissues
What is pathology
the study of diseases cells and tissues
What is disease associated with?
disruption of normal structure and function of tissues
What induces alterations in tissue architecture?
infection,heat/cold, poison/drugs, genetic and congenital changes, ageing/wear and tear, cancers
What do light microscopes reveal
basic cellular structure
What do electron microscopes reveal?
ultra-structure
What type of microscopy is commonly used in histology?
light microscopy
What is the first step in obtaining tissues for microscopy and describe what is it
SPECIMEN COLLECTION. Biopsies need to be taken
What is an incision/punch biopsy used for?
Collecting tissues from skin/oral surfaces
What is a needle biopsy for?
Organs or lumps below the skin
What is a endoscopic biopsy for?
For cavities inside body e.g. colonoscopy/endoscopy
What is the second step in obtaining tissues for microscopy and describe what it is.
FIXATION. Preserves the structural arrangement, terminates all biochemical reactions and prevents tissue decomposition.
Name 2 common fixatives
Formaldehyde and glutaraldehyde
What is step 3 in obtaining tissues for microscopy and describe it
DEHYDRATION. water is removed from tissues as paraffin embedding is not compatible with water. water is removed gradually to avoid distortion
What is the fourth step in obtaining tissues for microscopy and describe it
EMBEDDING. resins and paraffin wax used to support the tissue to allow thin sections to be cut from it. paraffin is not compatible with alcohol so alcohol is replaced by xylene.
What is the fifth step for obtaining tissues for microscopy and describe it
SECTIONING. tissue sections must be thin and flat and ideally a single layer of cells. sections are mounted on glass slides
What is the sixth step to obtaining tissues for microscopy and describe it
STAINING. makes cells and their components visible. allows identification of different cell and tissue features. Stains are not compatible with paraffin so reverse of dehydration occurs to remove paraffin wax and replace with water
What is haematoxylin and eosin
the most commonly used staining technique. haematoxylin (basic dye) stains acidic structures (nucleic acids) purple/blue and eosin (acidic dye) stains basic structures (cytoplasmic proteins) red or pink
What is the periodic acid-schiff reaction?
Stains complex carbohydrate magenta
What is masson trichome?
stains connective tissues. nuclei stains blue, collagen stains green/blue, cytoplasm, muscle, red blood cells and keratin stain red
What does immunohistochemistry do?
utilises antibody specificity for antigen.
What is the seventh step in obtaining tissues for microscopy and describe it
VIEWING. Permanent mounts are made. stained sections are dehydrated again to replace water with xylene. a mounting medium and a cover-slip seal protect section
