Specimen Nr. 02

Specimen:

Lymph node (Human being), High endothelial venule

Staining:

Toluidine blue, Semi-thin section

Magnification:

400x

Important structures :

1.	Basement membrane
2.	Endothelial cell
3.	Lumen of a high endothelial venule (HEV)
4.	Lymphocyte in lumen of a HEV
5.	Lymphocyte on endothelium of HEV
6.	Lymphocyte in endothelium of a HEV
7.	Lymphocyte in paracortical region

Der Ausschnitt zeigt den Paracortex eines Lymphknotens. Die postkapillären Venulen im Paracortex zeichnen sich dadurch aus, daß sie nicht durch ein flaches, sondern durch ein etwa isoprismatisches Endothel ausgekleidet sind. Deshalb werden sie hochendotheliale Venulen (HEV) genannt. Durch diese HEV gelangen Lymphozyten in den Paracortex des Lymphknotens. Von dort wandern sie in die anderen Kompartimente und verlassen schließlich über das Mark und die efferente Lymphe den Lymphknoten.

Legende:

	Basement membrane
	Endothelial cell
	Lumen of a high endothelial venule (HEV)
	Lymphocyte in lumen of a HEV
	Lymphocyte on endothelium of HEV
	Lymphocyte in endothelium of a HEV
	Lymphocyte in paracortical region

Semi-thin section

For semi-thin sections, the tissue is not embedded in paraffin (as is otherwise common for light microscopy), but in acrylic or epoxy resins, which are harder embedding substances, and permit thinner slices, so-called semi-thin slices of about 0.5 – max. 2µm in thickness, to be produced. After embedding in paraffin, a section is > 3µm thick. Semi-thin sections have better resolution under a light microscope than the thicker paraffin sections.

Embedding in epoxy resins is always performed when tissues are to be examined under a transmission electron microscope (TEM). Semi-thin sections are used to study the specimen under the light microscope before being examined under the transmission electron microscope (TEM).

Toluidine blue is primarily used to stain semi-thin sections since most dyes do not sufficiently infiltrate the epoxy resin. Toluidine blue stains various biologic components to different shades of blue.

HEV findet man in allen Lymphknoten, den Tonsillen, den Peyerschen Platten und der Appendix vermiformis. Im Verlauf von Immunreaktionen können sie auch in Geweben entstehen, die normalerweise keine HEV besitzen, zum Beispiel in der Synovialmembran von Gelenken und in der Haut. Über HEV wandern viele Lymphozyten vom Blut in das Gewebe ein. Etwa jeder dritte Lymphozyt, der eine HEV durchströmt, verläßt die Blutbahn und gelangt so in das entsprechende Organ.

HistoNet2000 - Help

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

2.Histologic specimen

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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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