Sinusoid (blood vessel)
|This article does not cite any sources. (December 2009) (Learn how and when to remove this template message)|
Scanning electron micrograph of a liver sinusoid with fenestrated endothelial cells. Fenestræ are approx 100 nm in diameter.
Blood vessels are the tubes which are two types arteries and veins. A sinusoid is a small blood vessel that is a type of capillary similar to a fenestrated endothelium. Sinusoids are actually classified as a type of open pore capillary (or discontinuous) as opposed to continuous and fenestrated types. Fenestrated capillaries have diaphragms that cover the pores whereas open pore capillaries lack a diaphragm and just have an open pore. The open pores of endothelial cells greatly increase their permeability. In addition, permeability is increased by large inter-cellular clefts and fewer tight junctions. The level of permeability is such as to allow small and medium-sized proteins such as albumin to readily enter and leave the blood stream.
Sinusoids are found in the liver, lymphoid tissue, endocrine organs, and hematopoietic organs such as the bone marrow and the spleen. Sinusoids found within terminal villi of the placenta are not comparable to these because they possess a continuous endothelium and complete basal lamina. This word was first used in 1893.
- Liver sinusoids, which help hepatocytes transport a small number of molecules to and from the blood stream.
|This cardiovascular system article is a stub. You can help Wikipedia by expanding it.|