2023年10月30日 · Postcapillary venules are formed when two or more capillaries unite. They typically range from 10–30 μm in diameter. Their walls, comprising mainly endothelium and occasional pericytes, enable the exchange of fluid, nutrients and other substances between blood and the interstitial fluid.

Postcapillary venules are the largest part of vessels within the papillary dermis and represent the place where inflammatory cells move from the intravascular to the interstitial space and where acute inflammation occurs.

High endothelial venules (HEV) are specialized post-capillary venules characterized by plump endothelial cells as opposed to the usual flatter endothelial cells found in regular venules. [1] HEVs enable lymphocytes circulating in the blood to directly enter a lymph node (by crossing through the HEV).

Post-capillary venules have a single layer of endothelium surrounded by a basal lamina. Their size is between 10 and 30 micrometers and are too small to contain smooth muscle. They are instead supported by pericytes that wrap around them. [1]

Post-capillary venules consist of an endothelial cell tube and basement membrane with no overlying VSMCs in their walls. Instead, post-capillary venules are covered by a layer of pericytes (Rhodin, 2014; Shepro & Morel, 1993; Simionescu & Simionescu, 1984).

These postcapillary venules represent the segment of the microvasculature that is most reactive to inflammation and contain intercellular endothelial junctions that can open to allow plasma proteins and circulating cells (leukocytes) to escape from the bloodstream.

Only capillaries and postcapillary venules are considered to be exchange microvessels, where capillaries serve as the major site for fluid passage, and postcapillary venules are the primary location for leukocyte diapedesis and plasma protein leakage, processes often seen under stimulated or inflammatory conditions.

Venules. A venule is an extremely small vein, generally 8–100 micrometers in diameter. Postcapillary venules join multiple capillaries exiting from a capillary bed. Multiple venules join to form veins.

The movement of leukocytes into extravascular spaces, also known as leukocyte migration, also occurs in postcapillary venules (Standring, 2016). Muscular venules are not involved in gas and solute exchange due to their more substantial wall thickness.

2021年7月5日 · Thus, post-capillary venules are the point-of-least resistance at the BBB, and compared to capillaries, provide a more feasible route for nanoparticle drug carriers into the brain.