histology (the cell) Flashcards
what is histology
study of tissues of the body and how these tissues are arranged to constitute organs
- histo is greek word meaning “web”
what are tissues composed of
several types of cell specific associations between cell and the ECM
ECM: consists of macromolecules such as collagen fibrils and basement membrane
what are the 4 steps of tissue preparation for study? (dont explain them yet)
1. Fixation: purpose is to preserve tissue structure with the least possible alteration
- ex. formalin (10% solution), osmium, glutaraldehyde for electron microscopy
2. Embedding: tissue is too soft to cut so you need to harden it
- dehydration and clearing
3. Sectioning: tissue block is basically cut into thin slices through the use of a microtome
4. Staining: cells and ECM are naturally colorless so to see them, need to stain them
- common stains: hematoxylin & eosin (H&E)
most commonly used fixative for tissue preparation is what
formalin 10% solution
briefly explain the process of embedding and sectioning
- Dehydration: tissue is dehydrated using ethanol to extract water
- Clearing: Uses xylene to replace the ethanol, making the tissue miscible with paraffin
- Tissue is then placed in melted paraffin, which infiltrates the tissue as the xylene evaporates, completing the embedding process
- Microtome: paraffin-embedded tissue is used to create paraffin blocks, when can then be sliced using a microtome into thin sections
- Tissues are mounted in a slide and allowed to dry in an oven before they are ready to be stained
Most common dehydration agent in tissue fixation
ethanol
most common embedding agent in tissue fixation
paraffin
most common clearing agent in tissue fixation
xylene
when are resins used an embedding medium in tissue fixation
used when you want to make very thin sections as in electron microscopy
- used instead of paraffin
