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#REDIRECT ] |
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{{Article for deletion/dated|page=Double circulatory system|timestamp=20150820150439|year=2015|month=August|day=20|substed=yes}} |
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{{Unreferenced|date=December 2009}} |
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{{infobox anatomy |
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| Name = Double circulatory system |
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| Image = 2101 Blood Flow Through the Heart.jpg |
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| Caption = The '''double circulatory system''' of the ]s (''seen above'') and ] (''bottom'') is present in the human ]. |
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]A <nowiki>'''</nowiki>double circulatory system<nowiki>'''</nowiki>, often called a <nowiki>'''</nowiki>double-loop circulatory system<nowiki>'''</nowiki> refers to two distinct and separate circulatory pathways for <nowiki>]</nowiki> flow. In a first order circulatory circuit, often called the <nowiki>''</nowiki><nowiki>]</nowiki><nowiki>''</nowiki>, <nowiki>]</nowiki> is pumped to the <nowiki>]</nowiki>s, thus acquiring <nowiki>]</nowiki> while simultaneously releasing <nowiki>]</nowiki>. Fully oxygenated blood then enters the second order circuit, called the <nowiki>''</nowiki><nowiki>]</nowiki><nowiki>''</nowiki>, going to the brain and body. The second order systemic output blood is selectively deoxygenated by the needs of the peripheral organs, returning once again to the <nowiki>]</nowiki> where it returns to the lungs to become oxygenated again. A double-loop system is also a <nowiki>]</nowiki> because blood usually travels in the body through distinct <nowiki>]</nowiki>s. |
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==Structure== |
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This distinction is shared by most vertebrates to varying degrees to include ]ns, ]s and ]s (including ]s.) In contrast, ] have a ''single circulation system'' because they lack lungs. Most animals living above the water require a double circulatory system to allow the added benefit of direct oxygenation from a developed pulmonary circuit. ] of the human circulatory system is an advanced study of the double circulatory system as the distinction between the right and left portions of the heart is founded. |
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For example, the adult human ] consists of two separated pumps or flow circuits. One side is dedicated to the ] and ] (which pumps ''deoxygenated'' blood into the pulmonary circulation). This circuit is very low in pressure incumbent upon systemic resistance. The left circuit inclusive of the left atrium and ventricle (which pumps ''oxygenated'' blood into the systemic circulation) is better gated to high pressure. Blood in one circuit must go through the heart to enter the other circuit. |
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Mathematics remain murky but it appears that summation of imaged Right Ventricular Ejection Fraction plus Left Ventricular Ejection Fraction may not allow a solution of 100% in many cases. European models of ] physiology appear to offer additional mathematical illumination of ]. |
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Blood circulates through the body at speeds which vary a factor of one hundred, from 1.2 m/s in the aorta to approximately 1.1 cm/s in the ]. Blood ] is similarly highly variable. Velocities generated within the large bore heart chambers vary considerable from velocities within the smaller bore vessels of the periphery and lungs. The circulatory system features numerous return paths (out to the kidneys and back, to the liver and back, to the legs and back, etc.), so it is incorrect to think of blood cells travelling the ''entire'' circulatory distance. The average adult heart pumps approximately 5 L/min of blood at rest (the ]); with a total blood volume of approximately 5L in an average adult, a blood cell will run through the complete circuit about once a minute, though this depends on what tissue it circulates to. For example, blood supplying the ] of the heart muscle itself will return to the pulmonary loop much faster than blood supplying the toes. During intense exercise, the ] can increase fivefold. |
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==Regulation of circulation== |
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Throughout the circulatory system there are many valves. There are 3 main types. The first is the bicuspid valve (mitral valve) which is found between the left atrium (auricle) and the left ventricle. This valve allows oxygenated blood to flow from the left atrium into the left ventricle during ventricular relaxation ]. The bicuspid valve also prevents the backflow of blood into the left atrium during ventricular contraction (systole). Then there is the tricuspid valve which is found between the right atrium and the right ventricle. This valve allows deoxygenated blood to flow from the right atrium into the right ventricle during ventricular relaxation. It prevents the backflow of blood into the right atrium during ventricular contraction. Finally there are the two semilunar valves, found at the beginning of the arteries leaving the heart. It is called a double circulatory system because it has two loops, one from the heart to the lungs and one from the heart to the rest of the body. |
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In a first order circulatory circuit, blood is pumped to the lungs, thus acquiring oxygen while simultaneously releasing carbon dioxide. Fully oxygenated blood then enters the second order circuit, going to the brain and body. The second order systemic output blood is selectively deoxygenated by the needs of the peripheral organs, returning once again to the heart. |
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The advantage of a double circulatory system is that blood can be pumped simultaneously into low pressure/compliance (pulmonary/right) and high pressure/compliance (systemic/left) loops. |
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==See also== |
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* ] |
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* ] |
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{{Cardiovascular_system}} |
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{{DEFAULTSORT:Double Circulatory System}} |
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] |
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