Im rasterelektronenmikroskopischen Bild des Knochenmarks ist die pralle Kugelform der Fettzellen, die durch das eingelagerte Fett zustandekommt, gut zu erkennen. Auch das lockere faserige Bindegewebe, das die Fettzellen wie eine Hülle überzieht, ist sichtbar ? wenn auch teils durch die Präparation zerstört. Die kleinen glattwandigen Kugeln sind Kunstprodukte: Bei der Anfertigung des Präparates sind einige Fettzellen geplatzt. Dabei ist das Fett in Tröpfchen frei geworden.

Legende:

	Adipose cell
	Free lipid droplets
	Loose fibrous connective tissue

Scanning electron microscope (SEM)

It is not necessary to prepare ultra-thin sections for examinations under the scanning electron microscope because the electron beam does not penetrate the object, in contrast to transmission electron microscope (TEM).

The SEM image is created directly by a point-to-point visualization of the surface details of the specimen. To achieve this effect, a very thin electron beam scans the surface of the specimen line by line. Each surface point emits secondary electrons whose different intensities are measured by a detector.

When preparing tissue specimens for a scanning electron microscopic examination, the specimens are dried instead of embedded and sliced after fixation and dehydration.

The dehydration technique commonly used today is critical-point drying. The dried specimens are then coated with gold in a vacuum, the so-called sputtering apparatus. This covers the specimen with a surface which can emit secondary electrons.

Fettgewebe kann auch die Funktion eines Füllgewebes oder eines Platzhalters haben. Im Knochenmark der langen Röhrenknochen von Erwachsenen tritt Fettgewebe als Füllgewebe an Stelle des zurückgebildeten roten blutbildenden Knochenmarks auf. Bei der Milchdrüse hingegen ist das Fettgewebe Platzhalter für die spätere Entwicklung des aktiv sezernierenden Drüsengewebes.

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

4. General Program Functions

Home: returns you to the “start” page
Tutor: how to contact the HistoNet Team
Help: Instructions for Use appear
Exit: closes down the HistoNet program
Boxes: goes back to the other specimen of a topic
VM: provides virtual microscopy

We hope you will enjoy working with HistoNet2000 and learn a lot from it!

Specimen Nr. 09

Specimen:

Staining:

Magnification:

Important structures :

Legende:

Scanning electron microscope (SEM)

HistoNet2000 - Help