Histology Flashcards
what is pathology
microscopic study of diseased cells and tissues
what is histology
microscopic study of normal cells and tissues
levels of structural organism
cells, tissues, organs, body systems
what is a tissue
a group of similar cells organised into tissues to perform a similar function
epithelial tissue
barrier and lining tissue. Outer layer of skin
Connective tissue
Structural and functional support. Cartilage, bone and blood
Muscle Tissue
Specialised for contraction. Cardiac cells
Nervous tissue
Carry information through the body via electrical impulses. Nerves
Microscope
Tissue samples are illuminated by a beam of light (light microscope) or electrons (electron microscope)
LM
reveal basic cellular structure, 0.2 micro metres. More commonly used for routine histopathology
EM
can reveal ultrastructure. 1nm (200 folds greater).
Microscopy stages
Specimen collection, fixation, dehydration, embedding, sectioning, staining, viewing
Specimen collection
incision or punch biopsy - skin/oral surfaces
Needle biopsy - organs or lumps below the skin. Imaging techniques (x ray, mri) are often used to guide
Endoplasmic - flexible tubes
Fixation
preserves the structural arrangement between cells and extracellular components. Terminates all biochemical reactions and so prevents tissue decompostion. Fixatives include formaldehyde and glutar
Dehydration
Praffin embedding not compatible with water. water removed from tissue using series of graded alcohols. Water removed gradually to prevent distortion
Embedding
Thin tissue section needed. But most tissues are delicate. Tissues must be supported to allow thin sections to be cut. Resins and Paraffin wax used
Sectioning
Tissue sections must be thin and flat, ideally a single layer of cells. Tissue sections should be transparent, embedded specimens are sectioned using a microtome, sections approximately
Staining
Most cells are colourless and transparent, staining makes cells and their components visible
Commonly used staining procedures
Haematoxylin and Eosin (H and E)
Describe staing procedure
Haematoxylin is a basic dye which stains acidic structures like nucleic acids blue/purple
Eosin is acidic and stains basic structures (such as cytoplasmic proteins) red or pink
Periodic acid-schiff reaction (PAS)
Stains complex carboydrate magenta. Mucins produced by goblet cells, brush borders and basement membranes are all PAS-positive
Masson trichrome
Stains conective tissues. Nuclei are other basophilic structures stain blue/purple. Collagen stains green/blue. Cytoplasm, muscle, red blood cells and keratin stain red
Immunohistochemistry
Antibodies are required to identify substance of interest. Utilises antibody specificity for antigen. Antiboody conjugated to an indicator conjugated to an indicator (e
