1. Introduction to Histology

Covered introduction to histology and started the review of cell nucleus.
Brief notes.


Histology - a science of the tissues.

Basic tissues:
1. epithelial
2. connective
3. nervous
4. muscle
Mõtle, kas tean: For example where do liver belong to?


Three primary components that make up the body tissue:
1.cells
2.intercellular (extracellular) matrix (produced by the cells of connective tissue)
3.body fluids (blood plasma, interstitial fluid, lymph).

• preparation of histologic sections

Routinely prepared by the paraffin technique. If tissues need to be examined without delay, tissue freezing is used (f.e. the course of surgical procedure depends on rapid histological assessment of the nature or spead of a diseased tissue).

• coloring of stains

Histological stains reveal tissue components either by coloring them selectively (LM) or by increasing their optical densities to different extents (EM).

Hematoxylin-eosin stained sections:

a)hematoxylin (basic/cationic stain) colors the acidic components (basophilic) of the cell a bluish-purple color (DNA, RNA);

b)eosin (acid/anionic stain) colors basic (acidophilic) components of the cell a pinkish colors (positive (e.g.NH3) sites on fixed proteins).

• light microscope (LM)

The max magnification about x 1400. The limit of resolution 0,2 mcm (details that are less than 0,2 mcm apart cannot be distinguished as separate entities.)

• elecron microscopy (EM)

Magnification up to x 50000, resolution 1 nm. a)transmission EM (routinely used);

b)scanning EM.

• interpreting histologic sections in three dimensions (transverse, longitudinal, oblique and grazing sections).

Mõtle: microscopic appearance of tubes, partitions, proteins, stored carbohydrates, stored fat.

Recognition of extracellular matrix and bodu fluids in sections.

Artifacts (postmortem degeneration, shrinkage artifact, precipitate, wrinkles or folds, microtome knife nicks, rough handling).

• localization of specific tissue constituents

Mõtle: fluorescence microscope, immunofluorecence staining, confocal microscope, blotting techiques and in situ hybridization (Northern, Southern and Western Blots).