part of blood vessel endothelial cell endothelial cell endothelial cell of sinusoid 2010-09-14T10:57:26Z FMA:63134 An endothelial cell that lines any of the venous cavities through which blood passes in various glands and organs such as the spleen and liver. Endothelial cells of sinusoids, often referred to as sinusoidal endothelial cells (SECs), are a specialized type of endothelial cell that primarily reside in the capillaries of the liver, spleen, and bone marrow. These cells form the innermost monolayer of the sinusoidal blood vessels, also known as sinusoids, that mediate the exchange of nutrients, metabolites, and waste materials between the blood and the surrounding organ tissue. SECs possess distinctive morphological features including a large, flattened shape, an abundance of fenestrations or pores, and the lack of a continuous basement membrane. These structural characteristics distinguish sinusoidal endothelial cells from other, more regularly structured endothelial cells in the body. Due to their special fenestrated structure, SECs facilitate the exchange of macromolecules, like lipoproteins and hyaluronan, between plasma and the surrounding organ parenchymal cells. These fenestrations act like sieves, allowing the passage of substances based on their size and charge. It's noteworthy that the permeability characteristics of SECs can be regulated dynamically according to the body's homeostatic needs. Beyond their key role in exchange mechanisms, endothelial cells of sinusoids are involved in several other functions. In the liver, for example, they help in the removal and endocytic degradation of waste macromolecules, immune response, and regulation of liver regeneration. They also participate in the formation and remodeling of blood vessels, a process known as angiogenesis. Additionally, in recent years, it has been discovered that these cells may have a role in disease conditions like cirrhosis and liver cancer. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) https://cellxgene.cziscience.com/cellguide/CL_0002262 Homo sapiens sinusoid