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Blood vessels function to transport blood to an animal's body tissues. In general, arteries and arterioles transport oxygenated blood from the lungs to the body and its organs, and veins and venules transport deoxygenated blood from the body to the lungs. Blood vessels also circulate blood throughout the circulatory system.
Endothelium lines the inner wall of vessels, shown here. Microscopic view showing endothelium (at top) inside the heart. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. This forms a barrier between vessels and tissues and control the flow of substances and fluid into and out of ...
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).
An anastomosis is a joining of two structures such as blood vessels. In the circulation these are called circulatory anastomoses, one of which is the join between an artery with a vein known as an arteriovenous anastomosis. This connection which is highly muscular, enables venous blood to travel directly from an artery into a vein without ...
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 Greek physician Galen (2nd century CE) knew blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions. [91] Galen, noting the heart as the hottest organ in the body, concluded that it provided heat to the body. [ 93 ]
Vasa vasorum are networks of small blood vessels that supply the walls of large blood vessels, such as elastic arteries (e.g., the aorta) and large veins (e.g., the venae cavae). The name derives from Latin 'the vessels of the vessels'.
The aorta is the largest blood vessel in human body. The aorta is the root systemic artery (i.e., main artery). In humans, it receives blood directly from the left ventricle of the heart via the aortic valve. As the aorta branches and these arteries branch, in turn, they become successively smaller in diameter, down to the arterioles.