The generic cell- intro to histology Flashcards
Tissue Preparation
- Fixation
- Embedding in paraffin
- Sectioning: slice into thin sections
- Mount slides
- Stain
Fixation
- Immersed in fixation immediately after removal from the body to preserve structure.
- Terminates cell metabolism, prevents enzymatic degradation of cells and tissues, and kills pathogenic microorganisms.
- Use Formalin
- Formalin slightly reacts with proteins but does not significantly alter their 3D structure.
Embedding and Sectioning
- Samples are cut into thin slices about one cell thick
- After fixation, specimens are embedded in paraffin to allow sectioning into slices
Differences between living and prepared tissue
Fixation process causes large molecules to be lost: -Neutral lipids -Glycogen -Proteoglycans -Glycosaminoglycans Paraffin section preparation causes loss of soluble components -Ions -Small molecules
Components that remain even after mounting on a slide
Nucleoproteins: formed from nucleic acids bound to protein
Intracellular cytoskeletal proteins
Extracellular proteins: in large insoluble aggregates
Membrane phospholipid-protein (or carbohydrate) complexes
Staining
- Paraffin is colorless so need to stain slides
- Histochemical and cytochemical procedures are based on specific binding of a dye or a fluorescent dye labeled antibody with a specific cell component
The cell
- The basic structural and functional unit of all multicellular organisms.
- Specialized activity/function of a cell is reflected by shape, organization in respect to other cells, products, and relative amounts of specific structural components.
Resolving power
The ability of a microscope lens or optical system to produce separate images of closely positioned objects.
Electron microscopy
- Transmission electron micrography: increases the resolution by a factor of 1000 relative to light microscopy
- Scanning electron microscopy: used to study the surface appearance of a structure
Cellular components lost during routine fixing and staining:
- Neutral lipids
- Glycogen
- Proteoglycans and glycosaminoglycans
Structures preserved during preparation and staining
- Nucleoproteins
- Cytoskeletal proteins
- Extracellular proteins in large insoluble aggregates
- Membrane phospholipid-protein (or carb) complexes
Plane of section
-We see different images depending on the cut and direction of the cut
Hematoxylin
- Basic
- Blue
Eosin
- Acidic
- Red
Basic dyes
- Carry a net positive charge
- Interact with negatively charged components of cells and tissues
- The ability of anionic groups to react with a basic dye: basophilia
- Hematoxylin
Anionic molecules (Neg charged)
- React with basic dyes
- Phosphate groups of nucleic acids
- Sulfate groups of glycosaminoglycans
- Carboxyl groups of proteins
Acidic dyes
- Carry a net negative charge
- Interact with positively charged components
- Especially ionized amino groups of proteins
- Acidophilia: Reaction of cationic groups with an acidic dye
- Eosin
Eosinophilic
Cells/tissues that contain many positive charges stain strongly with eosin
Basophilia components
- Chromatin and nucleoli in the nucleus
- Ribosomal RNA in the cytoplasm
- These components are basophilic due to the large amount of negatively charged phosphate groups
Chromatin
- Complex of DNA and protein that allows for tight packing of chromosomes in the nucleus
- Heterochromatin: Condensed, DNA not being transcribed
- Euchromatin: Dispersed, transcriptionally active, cannot be seen via light microscopy
Substances that react to eosin
- Cytoplasmic filaments
- Intracellular membranous components
- Unspecialized cytoplasm
- Extracellular fibers
Golgi apparatus
Functions in post translational modification, sorting, packaging of proteins for secretion or insertion into a cell membrane.
- A cell that is actively making large amounts of protein for secretion has a well developed Golgi
- Euchromatin
