Arteries contrast withveins, which carry deoxygenated blood back towards the heart; or in the pulmonary and fetal circulations carry oxygenated blood to the lungs and fetus respectively.
Large arteries (such as the aorta) are composed of many different types of cells, namely endothelial, smooth muscle, fibroblast, and immune cells.[2] As with veins, the arterial wall consists of three layers called tunics, namely thetunica intima,tunica media, andtunica externa, from innermost to outermost. Theexterna, alternatively known as thetunica adventitia, is composed ofcollagen fibers andelastic tissue—with the largest arteries containingvasa vasorum, small blood vessels that supply the walls of large blood vessels.[3] Most of the layers have a clear boundary between them, however the tunica externa has a boundary that is ill-defined. Normally its boundary is considered when it meets or touches the connective tissue.[4] Inside this layer is thetunica media, which is made up ofsmooth muscle cells,elastic tissue (also calledconnective tissue proper) andcollagen fibres.[3] The innermost layer, which is in direct contact with the flow of blood, is thetunica intima. The elastic tissue allows the artery to bend and fit through places in the body. This layer is mainly made up ofendothelial cells (and a supporting layer ofelastin richcollagen in elastic arteries). The hollow internal cavity in which the blood flows is called thelumen.
Arteries form part of thecirculatory system. They carryblood that is oxygenated after it has been pumped from theheart.Coronary arteries also aid the heart in pumping blood by sending oxygenated blood to the heart, allowing the muscles to function. Arteries carry oxygenated blood away from the heart to the tissues, except forpulmonary arteries, which carry blood to thelungs for oxygenation (usuallyveins carry deoxygenated blood to the heart but thepulmonary veins carry oxygenated blood as well).[6] There are two types of unique arteries. Thepulmonary artery carries blood from the heart to thelungs, where it receives oxygen. It is unique because the blood in it is not "oxygenated", as it has not yet passed through the lungs. The other unique artery is theumbilical artery, which carries deoxygenated blood from a fetus to its mother.
Arteries have ablood pressure higher than other parts of the circulatory system. The pressure in arteries varies during thecardiac cycle. It is highest when theheart contracts and lowest whenheart relaxes. The variation in pressure produces apulse, which can be felt in different areas of the body, such as theradial pulse.Arterioles have the greatest collective influence on both local blood flow and on overall blood pressure. They are the primary "adjustable nozzles" in the blood system, across which the greatest pressure drop occurs. The combination of heart output (cardiac output) andsystemic vascular resistance, which refers to the collective resistance of all of the body'sarterioles, are the principal determinants of arterial blood pressure at any given moment.
Arteries have the highest pressure and have narrow lumen diameter.[clarification needed]
Systemic arteries are the arteries (including theperipheral arteries), of thesystemic circulation, which is the part of thecardiovascular system that carriesoxygenatedblood away from the heart, to thebody, and returns deoxygenated blood back to the heart. Systemic arteries can be subdivided into two types—muscular and elastic—according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina. The larger arteries (>10 mm diameter) are generally elastic and the smaller ones (0.1–10 mm) tend to be muscular. Systemic arteries deliver blood to thearterioles, and then to thecapillaries, where nutrients and gasses are exchanged.
After traveling from theaorta, blood travels through peripheral arteries into smaller arteries calledarterioles, and eventually tocapillaries.Arterioles help in regulatingblood pressure by the variable contraction of thesmooth muscle of their walls, and deliver blood to thecapillaries. This smooth muscle contraction is primarily influenced by activity of the sympathetic vasomotor nerves innervating the arterioles.[7][8] Enhanced sympathetic activation prompts vasoconstriction, reducing the lumen diameter. A reduced lumen diameter consequently elevates the blood pressure within the arterioles.[9] Conversely, decreased sympathetic activity within the vasomotor nerves causes vasodilation of the vessels thereby decreasing blood pressure.[10]
Theaorta is the largest blood vessel in the human body.
Theaorta is the rootsystemic artery (i.e., main artery). In humans, it receives blood directly from the leftventricle of the heart via theaortic valve. As the aorta branches and these arteries branch, in turn, they become successively smaller in diameter, down to thearterioles. Thearterioles supplycapillaries, which in turn empty intovenules. The first branches off of the aorta are thecoronary arteries, which supply blood to the heart muscle itself. These are followed by the branches of the aortic arch, namely thebrachiocephalic artery, theleft common carotid, and theleft subclavian arteries.
Thecapillaries are the smallest of the blood vessels and are part of themicrocirculation. The microvessels have a width of a single cell in diameter to aid in the fast and easydiffusion of gasses, sugars and nutrients to surrounding tissues. Capillaries have nosmooth muscle surrounding them and have a diameter less than that ofred blood cells; a red blood cell is typically 7 micrometers outside diameter, capillaries typically 5 micrometers inside diameter. The red blood cells must distort in order to pass through the capillaries.
These small diameters of the capillaries provide a relatively large surface area for the exchange of gasses and nutrients.
Systemic arterial pressures are generated by the forceful contractions of the heart'sleft ventricle. Highblood pressure is a factor in causing arterial damage. Healthy resting arterial pressures are relatively low, mean systemic pressures typically being under 100 mmHg (1.9 psi; 13 kPa) above surroundingatmospheric pressure (about 760 mmHg, 14.7 psi, 101 kPa at sea level). To withstand and adapt to the pressures within, arteries are surrounded by varying thicknesses ofsmooth muscle which have extensive elastic and inelasticconnective tissues. The pulse pressure, being the difference betweensystolic anddiastolic pressure, is determined primarily by the amount of blood ejected by each heart beat,stroke volume, versus the volume and elasticity of the major arteries.
Ablood squirt, also known as an arterial gush, is the effect when an artery iscut due to the higher arterial pressures. Blood is spurted out at a rapid, intermittent rate, that coincides with the heartbeat. The amount ofblood loss can be copious, can occur very rapidly, and be life-threatening.[11]
Accidental intra-arterial injection eitheriatrogenically or through recreational drug use can cause symptoms such as intense pain,paresthesia andnecrosis. It usually causes permanent damage to the limb; oftenamputation is necessary.[14]
Among theAncient Greeks beforeHippocrates, all blood vessels were called Φλέβες,phlebes. The wordarteria then referred to thewindpipe.[15]Herophilos was the first to describe anatomical differences between the two types of blood vessel. WhileEmpedocles believed that the blood moved to and fro through the blood vessels, there was no concept of thecapillary vessels that join arteries and veins, and there was no notion of circulation.[16]Diogenes of Apollonia developed the theory ofpneuma, originally meaning just air but soon identified with thesoul itself, and thought to co-exist with the blood in the blood vessels.[17] The arteries were thought to be responsible for the transport of air to the tissues and to be connected to thetrachea. This was as a result of finding the arteries of cadavers devoid of blood.
In medieval times, it was supposed that arteries carried a fluid, called "spiritual blood" or "vital spirits", considered to be different from the contents of theveins. This theory went back toGalen. In the late medieval period, thetrachea,[18] andligaments were also called "arteries".[19]
William Harvey described and popularized the modern concept of the circulatory system and the roles of arteries and veins in the 17th century.
Alexis Carrel at the beginning of the 20th century first described the technique for vascular suturing and anastomosis and successfully performed manyorgan transplantations in animals; he thus actually opened the way to modernvascular surgery that was previously limited to vessels' permanent ligation.
^Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1999).Human Biology and Health. Englewood Cliffs, New Jersey: Prentice Hall.ISBN0-13-981176-1.
^Schwarzwald, Colin C.; Bonagura, John D.; Muir, William W. (2009-01-01), Muir, William W.; Hubbell, John A. E. (eds.),"Chapter 3 - The Cardiovascular System",Equine Anesthesia (Second Edition), Saint Louis: W.B. Saunders, pp. 37–100,ISBN978-1-4160-2326-5, retrieved2023-11-17
^Bertazzo, S.et al. Nano-analytical electron microscopy reveals fundamental insights into human cardiovascular tissue calcification.Nature Materials12, 576-583 (2013).
^Miller, J. D. Cardiovascular calcification: Orbicular origins.Nature Materials12, 476-478 (2013).
^Sen MD, Surjya; Nunes Chini MD Phd, Eduardo; Brown MD, Michael J. (June 2005)."Complications After Unintentional Intra-arterial Injection of Drugs: Risks, Outcomes, and Management Strategies"(Online archive of Volume 80, Issue 6, Pages 783–795, June 2005 Mayo Clinic Proceedings).Mayo Clinic Proceedings.80 (6). MAYO Clinic:783–95.doi:10.1016/S0025-6196(11)61533-4.PMID15945530. Retrieved25 August 2014.Unintentional intra-arterial injection of medication, either iatrogenic or self-administered, is a source of considerable morbidity. Normal vascular anatomical proximity, aberrant vasculature, procedurally difficult situations, and medical personnel error all contribute to unintentional cannulation of arteries in an attempt to achieve intravenous access. Delivery of certain medications via arterial access has led to clinically important sequelae, including paresthesias, severe pain, motor dysfunction, compartment syndrome, gangrene, and limb loss. We comprehensively review the current literature, highlighting available information on risk factors, symptoms, pathogenesis, sequelae, and management strategies for unintentional intra-arterial injection. We believe that all physicians and ancillary personnel who administer intravenous therapies should be aware of this serious problem.
^The heart and the vascular system in ancient Greek medicine. From Alcmaeon to Galen. Oxford University Press 1973, special edition for Sandpiper Books 2001. ISBN 0-19-858135-1 p.24
^The heart and the vascular system in ancient Greek medicine. From Alcmaeon to Galen. Oxford University Press 1973, special edition for Sandpiper Books 2001. ISBN 0-19-858135-1 p.18
^The heart and the vascular system in ancient Greek medicine. From Alcmaeon to Galen. Oxford University Press 1973, special edition for Sandpiper Books 2001. ISBN 0-19-858135-1 p.26
^Shakespeare, William. Hamlet Complete, Authoritative Text with Biographical and Historical Contexts, Critical History, and Essays from Five Contemporary Critical Perspectives. Boston: Bedford Books of St. Martins Press, 1994. pg. 50.
