Endothelial in the context of "Platelet-activating factor"

Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the permeability of a blood vessel wall–in other words, the blood vessel wall's capacity to allow for the flow of small molecules (such as drugs, nutrients, water, or ions) or even whole cells (such as lymphocytes on their way to a site of inflammation) in and out of the vessel. Blood vessel walls are lined by a single layer of endothelial cells. The gaps between endothelial cells (cell junctions) are strictly regulated depending on the type and physiological state of the tissue.

There are several techniques to measure vascular permeability to certain molecules. For instance, the cannulation of a single microvessel with a micropipette: the microvessel is perfused with a certain pressure, occluded downstream, and then the velocity of some cells will be related to the permeability. Another technique uses multiphoton fluorescence intravital microscopy through which the flow is related to fluorescence intensity and the permeability is estimated from the Patlak transformation.

The blood–air barrier or air–blood barrier, (alveolar–capillary barrier or membrane) exists in the gas exchanging region of the lungs. It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli. It is formed by the type I epithelial lining cells of the alveolar wall, the endothelial cells of the capillaries and the fused basement membrane between, forming the alveolar basement membrane. The barrier is permeable to molecular oxygen, carbon dioxide, carbon monoxide and many other gases.

Cavernous hemangioma, also called cavernous angioma, venous malformation, or cavernoma, is a type of venous malformation due to endothelial dysmorphogenesis from a lesion which is present at birth. A cavernoma in the brain is called a cerebral cavernous malformation or CCM. Despite its designation as a hemangioma, a cavernous hemangioma is a benign (but not harmless) condition, not a malignant tumor, as it does not display endothelial hyperplasia. The abnormal tissue causes a slowing of blood flow through the cavities, or "caverns". The blood vessels do not form the necessary junctions with surrounding cells, and the structural support from the smooth muscle is hindered, causing leakage into the surrounding tissue. It is the leakage of blood (hemorrhage) that causes a variety of symptoms known to be associated with the condition.

In immunology, the mononuclear phagocyte system or mononuclear phagocytic system (MPS), also known as the macrophage system, is a part of the immune system that consists of the phagocytic cells located in reticular connective tissue. The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen. The Kupffer cells of the liver and tissue histiocytes are also part of the MPS. The mononuclear phagocyte system and the monocyte macrophage system refer to two different entities, often mistakenly understood as one.

"Reticuloendothelial system" is an older term for the mononuclear phagocyte system, but it is used less commonly now, as it is understood that most endothelial cells are not macrophages.