Histology Flashcards
(25 cards)
cytology
The study of the structure and function of cells
histology
The study of tissues/web. Now encompasses Cytology as the study of microscopic anatomy of cells
organology
study of microscopic association of organs
pathology
study of diseased/abnormal cells, tissues, and organs
Principle of Complementarity of Structure and Function
“function always reflects structure” . physiology always reflects anatomy.
levels of structural organization of human body from simple to complex
chemical-> cellular level-> tissue level-> organ level-> organ system level-> organismal level
primary tissue types
epithelial tissue, muscle tissue, connective tissue and nervous tissue
resolution
the distance that two objects must be separated from each other in order to be distinguished as two distinct objects
human eye light microscope SEM TEM Atomic force microscopy
human eye - 0.2 mm light microscope- 0.2 micrometers SEM- 2.5 nm TEM-0.05 nm/1.0 nm atomic force microscopy - 50.0 pm
Resolution dependent on
- optical system
- wavelength light source
- specimen thickness
- quality of fixation
- staining intensity
Steps for Light Microscopy
- Acquire Tissue or cells
- Fixation
- Processing
- Embedding
- Sectioning
- Staining
Fixation of tissues
fix tissues with a fixative (formalin) in order to stop metabolism, enzyme activity, and to fix proteins. Want to preserve morphology.
Processing
- Dehydration- replace water with alcohol
- Clearing- clear with xylene (misc. w/ alcohol and paraffin)
- Infiltration- infiltrate with liq. wax
embedding
Orient tissue in cassette in correct orientation w/ liquid wax. Move the tissue from the hot liquid to the cool section so that it can harden
Problems with Standard Technique for Light Microscopy
- Time
- Solvent dissolves lipids
- Shrinkage of tissues
How to solve time factor
use cryostat to fix the tissue (rapidly freeze). *Can monitor enzymatic activity because proteins are not cross-linked
How to avoid dissolving lipids
Need TEM. Perform double-fixation with gluteraldehyde and osmium tetroxide to preserve structure. Os. tetroxide binds to phospholipids
shrinkage of tissues
Use TEM: Perform double-fixation and then submerge into liquid plastic rather than wax.
Acidic Dyes
carry a net negative charge and bind with eosinophilic cell/tissue components (those with a net positive charge)
Pink. Eosin dye
Basic dyes
carry a net positive charge and bind with basophilic cell/tissue components (those that carry a net negative share) Blue. Hematoxylin dye
Fluorescence miscroscopy
probe with UV light and emit light of wavelengths that humans can see
phase-contrast microscopy
lens system that determines refractive indexes and changes in light speed as light passes through specimen. Can detect speed of light as passes through specimens and produces an indirect image
brightfieqld microscopy
light enters through bottom of microscope. Requires stain in order to view specimens
histochemistry and cytochemistry
localize cell structures by using enzyme activities and marker compound (use cryostat).
