Endothelium

Endothelium from the posterior tibial artery with intermediary filaments 1 ,  plasmalemma invaginations (caveolae or superficial vesicles) 2 , many intra-cellular vesicles 3 and Weibel-Palade bodies (Palade granules , multi vesicular bodies, MVBs) 4. Weibel-Palade bodies 4 are membrane-enclosed granules, which contain parallel tubular filaments. They are specialized secretory granules, which contain von Willebrand factor and the vasoconstriction peptide endothelin, among other factors. Apart from vimentin intermediary filaments, the endothelium also contains a contractile filament system ( actin-myosin system ). The two systems can be distinguishe d using immunohistochemistry.

1 Intermediary filaments

2 Caveolae

3 Vesicles

4 Weibel-Palade body (Palade granules)

5 Lysosomes

6 Intercellular gap

7 Basal membrane

8 Vascular lumen

Electron microscopy; magnification: × 4 4,200

Endothelium

Endothelium from the posterior tibial vein with intermediary filaments 1 ,  mitochondria 2 and vesicles 3 . Two endothelial cells, which are clearly separated by an intercellular space 4 overlap like roof shingles. Note the caveolae and the cytoplasmic vesicles 3 in the endothelial cells in the lower part of the photo.

1 Cytoskeleton (filaments)

2 Mitochondria

3 Vesicles

4 Intercellular gap

5 Lysosome

6 Elastic fiber s

7 Vascular lumen

Electron microscopy; magnification: × 28000

References

Kuehnel, W.(2003). Color Atlas of Cytology, Histology, and Microscopic Anatomy. 4^th edition . Institute of Anatomy Universitätzu Luebeck Luebeck, Germany . Thieme Stuttgart · New York .