Specimen Nr. 06

Specimen:

Nonmyelinated axons, Sciatic nerve (Rat)

Staining:

TEM

Magnification:

42 000x

Important structures :

1.Myelinated axon
2.Myelin sheath
3.Mesaxon
4.Cytoplasm of a Schwann cell
5.Nonmyelinated axon (completely enclosed)
6.Nucleus of Schwann cell
7.Basement membrane
8.Endoneurium (collagen fibrils in cross section)
9.Nonmyelinated axon (partially enclosed)
10.Section of fibrocyte process
Die Abbildung zeigt die Querschnitte zahlreicher markloser Axone sowie eines markhaltigen Axons. Am markhaltigen Axon ist das Mesaxon, eine Plasmalemmduplikatur der Schwann?schen Zelle zu sehen. Das Mesaxon ist eine Duplikatur des Plasmalemms, von der die Myelinwickelungen ausgehen. Auch die marklosen Axone sind einzeln in Einsenkungen des Zytoplasmas der Schwann?schen Zellen eingebettet. Oft sind die marklosen Axone vollständig von ?ihren? Schwann?schen Zellen umschlossen. In den Fällen, wo sie nur teilweise von der Schwann?schen Zelle umgeben sind, ist ein Teil des Axons nur von der Basalmembran bedeckt. Im Inneren der Axone sind zahlreiche Mikrotubuli und Neurofilamente zu beobachten. Das Endoneurium zeigt vorwiegend quer geschnittene kollagene Fibrillen.

Legende:

Myelinated axon
Myelin sheath
Mesaxon
Cytoplasm of a Schwann cell
Nonmyelinated axon (completely enclosed)
Nucleus of Schwann cell
Basement membrane
Endoneurium (collagen fibrils in cross section)
Nonmyelinated axon (partially enclosed)
Section of fibrocyte process

Myelinated axon (A) and Nonmyelinated axon (B)[Bo]

1. Axon
2. Schwann cell
3. Myelin sheath
4. Collagen fibrils
5. Nucleus of Schwann cell
6. Mesaxon

Transmission electron microscope (TEM)

The sections for examination under the transmission electron microscope are about 0.1µm thick. They are referred to as ultra-thin sections.

To obtain such ultra-thin sections, the tissues are embedded in plastic polymers like epon (instead of paraffin, which is used for examination under the light microscope) after fixation and dehydration. Ultra-thin sections are not stained with dyes, but contrasted with heavy-metal salts. The heavy-metal salts lead to a different electron scatter and thereby create a differentiated blackening of the photographic negative. A common method of creating contrast results with 5% uranyl acetate and lead citrate.

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Myelinated axon
Myelin sheath
Mesaxon
Cytoplasm of a Schwann cell
Nonmyelinated axon (completely enclosed)
Nonmyelinated axon (completely enclosed)
Nucleus of Schwann cell
Basement membrane
Endoneurium (collagen fibrils in cross section)
Nonmyelinated axon (partially enclosed)
Section of fibrocyte process

HistoNet2000 - Help

1. Organization of the screen surface

Right side: histologic specimen
Left side: information about the specimen (above) and general program functions (below)

2.Histologic specimen

Pull the mouse across the histologic specimen for training purposes. A small square with exclamation marks (dynamic labels) will appear where there is an important structure. You should then decide what structure this could be. To check your result, simply click the appropriate square, and the correct label will appear. The option “marked” allows you to see all labels for all structures simultaneously. These can be removed by clicking “unmarked”. This reactivates the dynamic labels.

3. Complementary information

Info: general information about the specimen, as well as a list of the dynamic labels
Drawing: schematic drawing of the specimen
Staining: information about the staining method for this specimen
Knowledge: short texts with basic histologic information, presently deactivated

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