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blood goes round and round

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-{{Citations missing|date=November 2007}}
-{{For|transport in plants|Vascular tissue}}
-{{Otheruses4|the organ system|the band|Circulatory System}}
-[[Image:Blutkreislauf.png|thumb|upright|200px|right|The human circulatory system.  Red indicates oxygenated blood, blue indicates deoxygenated.]]
-The '''circulatory system''' (or ''' cardiovascular system''') is an [[organ (anatomy)|organ system]] that moves nutrients, gases, and wastes to and from [[cell (biology)|cells]], helps fight diseases and helps stabilize body temperature and [[pH]] to  maintain [[homeostasis]]. While humans, as well as other [[vertebrates]], have a '''closed circulatory system''' (meaning that the blood never leaves the network of arteries, veins and capillaries), some [[invertebrate]] groups have '''open circulatory system'''. The most primitive animal [[phylum|phyla]] lack circulatory systems.
-==Human circulatory system==
-The main components of the human circulatory system are the [[heart]], the [[blood]], and the [[blood vessel]]s.  The circulatory system includes: the [[pulmonary circulation]], a "loop" through the [[lung]]s where blood is oxygenated; and the [[systemic circulation]], a "loop" through the rest of the body to provide [[oxygenate]]d blood. An average adult contains five to six quarts of blood, which consists of plasma that contains [[red blood cells]], [[white blood cells]], and [[platelets]].
-Two types of fluids move through the circulatory system: blood and lymph. The blood, heart, and blood vessels form the [[cardiovascular system]]. The lymph, lymph nodes, and lymph vessels form the [[lymphatic system]]. The cardiovascular system and the lymphatic system collectively make up the circulatory system.
-===Systemic circulation===
-{{Main|Systemic circulation}}
-Systemic circulation is the portion of the cardiovascular system which carries [[oxygen]]ated [[blood]] away from the [[heart]], to the [[body]], and returns deoxygenated blood back to the heart.
-[[Arteries]] always take blood away from the heart, regardless of their oxygenation, and [[vein]]s always bring blood back. In general, arteries bring oxygenated blood to the tissues; veins bring deoxygenated blood back to the heart. In the case of the [[pulmonary vessels]], however, the oxygenation is reversed: the [[pulmonary artery]] takes deoxygenated blood from the heart to the lungs, and oxygenated blood is pumped back through the [[pulmonary vein]] to the heart. As blood circulates through the body, oxygen and nutrients diffuse from the blood into cells surrounding the [[capillaries]], and carbon dioxide diffuses into the blood from the capillary cells.
-The release of oxygen from red blood cells or [[erythrocyte]]s is regulated in mammals. It increases with an increase of [[carbon dioxide]] in [[tissues]], an increase in temperature, or a decrease in pH. Such characteristics are exhibited by tissues undergoing high metabolism, as they require increased levels of [[oxygen]].
-===Pulmonary circulation===
-{{Main|Pulmonary circulation}}
-Pulmonary circulation is the portion of the cardiovascular system which carries [[oxygen]]-depleted [[blood]] away from the heart, to the [[lungs]], and returns oxygenated blood back to the heart.
-De-oxygenated blood enters the right atrium of the heart and flows into the right ventricle where it is pumped through the pulmonary arteries to the lungs. Pulmonary veins return the now oxygen-rich blood to the heart, where it enters the left atrium before flowing into the left ventricle. From the left ventricle the oxygen-rich blood is pumped out via the aorta, and on to the rest of the body.
-===Coronary circulation===
-{{Main|Coronary circulation}}
-The Coronary circulatory system provides a blood supply to the heart.
-===Heart===
-In the [[heart]] there is one [[atrium (heart)|atrium]] and one [[Ventricle (heart)|ventricle]] for each circulation, and with both a systemic and a pulmonary circulation there are four chambers in total: [[left atrium]], [[left ventricle]], [[right atrium]] and [[right ventricle]].
-===Closed circulatory system===
-The circulatory systems of humans is closed, meaning that the blood never leaves the system of [[blood vessels]]. In contrast, oxygen and nutrients diffuse across the blood vessel layers and enters [[interstitial fluid]], which carries oxygen and nutrients to the target cells, and carbon dioxide and wastes in the opposite direction.
-==Other vertebrates==
-The circulatory systems of all [[vertebrate]]s, as well as of [[annelid]]s (for example, [[earthworm]]s) and [[cephalopod]]s ([[squid]] and [[octopus]]) are ''closed'', just as in humans. Still, the systems of [[fish]], [[amphibian]]s, [[reptile]]s, and [[bird]]s show various stages of the [[evolution]] of the circulatory system.
-In fish, the system has only one circuit, with the blood being pumped through the capillaries of the [[gill]]s and on to the capillaries of the body tissues. This is known as ''single'' circulation. The heart of fish is therefore only a single pump (consisting of two chambers). In amphibians and most reptiles, a [[double circulatory system]] is used, but the heart is not always completely separated into two pumps. Amphibians have a three-chambered heart.
-Birds and mammals show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently from that of mammals.
-== Open circulatory system ==
-The '''open circulatory system''' is an arrangement of internal transport present in many animals such as [[mollusc]]s and [[arthropod]]s, in which fluid (called [[hemolymph]]) in a cavity called the [[hemocoel]] bathes the organs directly with oxygen and nutrients and there is no distinction between [[blood]] and [[interstitial fluid]]; this combined fluid is called hemolymph or haemolymph. Muscular movements by the animal during [[Animal locomotion|locomotion]] can facilitate hemolymph movement, but diverting flow from one area to another is limited. When the [[heart]] relaxes, blood is drawn back toward the heart through open-ended pores (ostia).
-Hemolymph fills all of the interior hemocoel of the body and surrounds all [[cell (biology)|cell]]s. Hemolymph is composed of [[water]], [[inorganic chemistry|inorganic]] [[salt]]s (mostly [[Sodium|Na<sup>+</sup>]], [[Chlorine|Cl<sup>-</sup>]], [[Potassium|K<sup>+</sup>]], [[Magnesium|Mg<sup>2+</sup>]], and [[Calcium|Ca<sup>2+</sup>]]), and [[organic chemistry|organic compounds]] (mostly [[carbohydrate]]s, [[protein]]s, and [[lipid]]s). The primary oxygen transporter molecule is [[hemocyanin]].
-There are free-floating cells, the [[hemocyte]]s, within the hemolymph. They play a role in the arthropod [[immune system]].
-== No circulatory system ==
-Circulatory systems are absent in some animals, including [[flatworms]] (phylum [[Platyhelminthes]]). Their [[body cavity]] has no lining or enclosed fluid. Instead a muscular [[pharynx]] leads to an extensively branched [[digestive system]] that facilitates direct [[diffusion]] of nutrients to all cells. The flatworm's dorso-ventrally flattened body shape also restricts the distance of any cell from the digestive system or the exterior of the organism. [[Oxygen]] can diffuse from the surrounding [[water]] into the cells, and [[carbon dioxide]] can diffuse out. Consequently every cell is able to obtain nutrients, water and oxygen without the need of a transport system.
-== Measurement techniques ==
-* [[Electrocardiogram]] - for cardiac electrophysiology
-* [[Sphygmomanometer]] and [[Stethoscope]] - for blood pressure
-* [[Pulse meter]] - for cardiac function (heart rate, rhythm, dropped beats)
-* [[Pulse]] - commonly used to determine the heart rate in absence of certain cardiac pathologies
-* [[Nail]] bed blanching test - test for perfusion
-* Vessel [[Canula]] or [[Catheter]] pressure measurement - pulmonary wedge pressure or in older animal experiments.
-== Health and disease ==
-{{main|Cardiovascular disease}}
-{{main|Congenital heart defect}}
-== History of discovery ==
-The valves of the heart were discovered by a physician of the Hippocratean school around the [[4th century BC]]. However their function was not properly understood then. Because blood pools in the veins after death, arteries look empty. Ancient anatomists assumed they were filled with air and that they were for transport of air.
-[[Herophilus]] distinguished veins from arteries but thought that the pulse was a property of arteries themselves. Erasistratus observed that arteries that were cut during life bleed. He ascribed the fact to the phenomenon that air escaping from an artery is replaced with blood that entered by very small vessels between veins and arteries. Thus he apparently postulated capillaries but with reversed flow of blood.
-The [[2nd century]] AD, Greek physician, [[Galen]], knew that blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions. Growth and energy were derived from venous blood created in the liver from chyle, while arterial blood gave vitality by containing pneuma (air) and originated in the heart. Blood flowed from both creating organs to all parts of the body where it was consumed and there was no return of blood to the heart or liver. The heart did not pump blood around, the heart's motion sucked blood in during diastole and the blood moved by the pulsation of the arteries themselves.
-Galen believed that the arterial blood was created by venous blood passing from the left ventricle to the right by passing through 'pores' in the interventricular septum, air passed from the lungs via the pulmonary artery to the left side of the heart. As the arterial blood was created 'sooty' vapors were created and passed to the lungs also via the pulmonary artery to be exhaled.
-In [[1242]], the [[Islamic medicine|Arabian physician]], [[Ibn al-Nafis]], became the first person to accurately describe the process of blood circulation in the human body, particularly [[pulmonary circulation]], for which he is considered the father of [[Cardiovascular physiology|circulatory physiology]].<ref>Chairman's Reflections (2004), "Traditional Medicine Among Gulf Arabs, Part II: Blood-letting", ''Heart Views'' '''5''' (2), p. 74-85 [80].</ref> Ibn al-Nafis stated in his ''Commentary on Anatomy in Avicenna's Canon'':
-<blockquote>"...the blood from the right chamber of the heart must arrive at the left chamber but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people thought or invisible pores as Galen thought. The blood from the right chamber must flow through the vena arteriosa ([[pulmonary artery]]) to the lungs, spread through its substances, be mingled there with air, pass through the arteria venosa ([[pulmonary vein]]) to reach the left chamber of the heart and there form the vital spirit..."</blockquote>
-Contemporary drawings of this process have survived. In [[1552]], [[Michael Servetus]] described the same, and [[Realdo Colombo]] proved the concept, but it remained largely unknown in Europe.
-Finally [[William Harvey]], a pupil of [[Hieronymus Fabricius]] (who had earlier described the valves of the veins without recognizing their function), performed a sequence of experiments and announced in [[1628]] the discovery of the human circulatory system as his own and published [[Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus|an influential book]] about it. This work with its essentially correct exposition slowly convinced the medical world. Harvey was not able to identify the capillary system connecting arteries and veins; these were later described by [[Marcello Malpighi]].
-== See also ==
-<div style="-moz-column-count:3; column-count:3;">
-* [[Cardiology]]
-* [[Lymphatic system]]
-* [[Blood vessels]]
-* [[Innate heat]]
-* [[Cardiac muscle]]
-* [[Major systems of the human body]]
-* [[Heart]]
-* [[Amato Lusitano]]
-* [[William Harvey]]
-</div>
-== References ==
-{{reflist}}
-== External links ==
-* [http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookcircSYS.html The Circulatory System], a comprehensive overview
-* [http://www.invisionguide.com/heart The InVision Guide to a Healthy Heart] An interactive website
-* [http://www.nature.com/ncpcardio/index.html NCP Cardiovascular Medicine] A Journal Covering Clinical Cardiovascular Medicine
-{{organ_systems}}
-{{cardiovascular_system}}
-{{Heart}}
-{{Cardiovascular physiology}}
-{{Development of circulatory system}}
-{{Circulatory system pathology}}
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