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In contrast to regular venules, high endothelial venules are a special type of venule where the endothelium is made up of simple cuboidal cells. Lymphocytes exit the blood stream and enter the lymph nodes via these specialized venules when an infection is detected. Compared with arterioles, the venules are larger with much weaker muscular coat.
The venous system apart from the post-capillary venules is a high volume, low pressure system. Vascular smooth muscle cells control the size of the vein lumens, and thereby help to regulate blood pressure. [31] The post-capillary venules are exchange vessels whose ultra-thin walls allow the ready diffusion of molecules from the capillaries. [10]
Disorders of capillary formation as a developmental defect or acquired disorder are a feature in many common and serious disorders. Within a wide range of cellular factors and cytokines, issues with normal genetic expression and bioactivity of the vascular growth and permeability factor vascular endothelial growth factor (VEGF) appear to play a ...
Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes.The endothelium provides a smooth surface for the flow of blood and regulates the movement of water and dissolved materials in the interstitial plasma between the blood and the tissues.
The capillaries connect to venules, and the blood then travels back through the network of veins to the venae cavae into the right heart. The micro-circulation — the arterioles, capillaries, and venules —constitutes most of the area of the vascular system and is the site of the transfer of O 2, glucose, and enzyme substrates into the
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).
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. [1] [2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and Latin vascula meaning vessels).
Blood viscosity is the thickness of the blood and its resistance to flow as a result of the different components of the blood. Blood is 92% water by weight and the rest of blood is composed of protein, nutrients, electrolytes, wastes, and dissolved gases.