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Blood vessels transport blood cells, ... Blood viscosity is the thickness of the blood and its resistance to flow as a result of the different components of the blood ...
The endothelium (pl.: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. [1] The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.
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).
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 formed elements are the two types of blood cell or corpuscle – the red blood cells, (erythrocytes) and white blood cells (leukocytes), and the cell fragments called platelets [12] that are involved in clotting. By volume, the red blood cells constitute about 45% of whole blood, the plasma about 54.3%, and white cells about 0.7%.
However, whether these cells differentiate into each other is an outstanding question in the field. Pericytes' regenerative capacity is affected by aging. [18] Such versatility is useful, as they actively remodel blood vessels throughout the body and can thereby blend homogeneously with the local tissue environment. [19]
A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the innermost layer of an artery or vein), consisting of a thin wall of simple squamous endothelial cells. [2]
The first entry of venous blood is from the convergence of two or more capillaries into a microscopic, post-capillary venule. [13] Post-capillary venules have a diameter of between 10 and 30 micrometres (μm), and are part of the microcirculation. Their endothelium is made up of flattened oval or polygon shaped cells surrounded by a basal lamina.