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The capillary wall performs an important function by allowing nutrients and waste substances to pass across it. Molecules larger than 3 nm such as albumin and other large proteins pass through transcellular transport carried inside vesicles , a process which requires them to go through the cells that form the wall.
A lineage relationship to other cell types has been proposed, including smooth muscle cells, [16] neural cells, [16] NG2 glia, [17] muscle fibers, adipocytes, as well as fibroblasts [18] and other mesenchymal stem cells. However, whether these cells differentiate into each other is an outstanding question in the field.
When pressure is greater in the interstitial fluid than in lymph, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary. When pressure is greater inside the lymphatic capillary, the cells adhere more closely, and lymph cannot escape back into the interstitial fluid.
The cell membrane is reduced to a single layer at the fenestrations, facilitating the movement of material through the vessel walls. Occasional (pericyte)s (Rouget cells), which may have a contractile function, are found around the capillary wall. Pericytes have the ability to alter local blood flow. The choriocapillaris is densest in the ...
Diffusion occurs through the walls of the vessels due to a concentration gradient, allowing the necessary exchange of ions, molecules, or blood cells. The permeability of a capillary wall is determined by the type of capillary and the surface of the endothelial cells. A continuous, tightly spaced endothelial cell lining only permits the ...
Differences in vascular permeability between normal tissue and a tumor. Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (lymphocytes on their way to the site of inflammation) in and out of the vessel.
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries. [1]Arterioles have muscular walls (usually only one to two layers of smooth muscle cells) and are the primary site of vascular resistance.
Capillary action of water (polar) compared to mercury (non-polar), in each case with respect to a polar surface such as glass (≡Si–OH). Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of external forces like gravity.