ISSN:
1432-0878
Keywords:
Gills
;
Tilapia mossambica
;
Arterio-venous anastomoses
;
Specialized endothelia
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Arterio-venous anastomoses (AVA) in gill filaments of Tilapia mossambica exhibit a distinct polarity. Two different types of highly specialized endothelial cells, both of epitheloid shape, line these vessels: Type I cells, contacting the arterial lumen, are elongated and about two to three times as large as type II endothelial cells. Their surface is increased by tentacular protrusions which reach far into the arterial lumen. Filament whorls forming tubelike structures with centrally located glycogen granules are abundant in these cells. Type II endothelial cells are located proximal to the central venous sinus (CVS). Their less abundant and more electron dense cytoplasm is free of filament whorls. There are also intermediate cell forms at approximately the middle of each anastomosis. Short cell processes protrude from all endothelial cell types into the AVA lumen. Outside the indistinct vascular basement lamina, a layer of cover cells tightly envelopes the AVA. These cells are, however, absent around the part of the AVA adjacent to the CVS. Here the endothelial cells are in immediate contact with the interstitium. Endothelial cells sheathed by cover cells reach the interstitium through basal foot processes. Nerve fibre bundles regularly come into close contact with the AVAs. Possible functions of the AVAs, including osmoreception are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00227011
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