In the first circuit, the blood is pumped to the lungs, where it acquires oxygen. It then returns to the heart and enters the second circuit, going to the rest of the body, eventually returning to the heart.

The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation in amphibians, birds and mammals (including humans.) In contrast, fish have a single circulation system. Image File history File links Blood_circulation_(human). ... Image File history File links Blood_circulation_(human). ... 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. ... Systemic circulation is the portion of the cardiovascular system which carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart. ... For other uses, see Amphibian (disambiguation). ... “Aves” redirects here. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the production of milk in female mammary glands and the presence of hair, three middle ear bones used in hearing, and a neocortex region in the... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: wise man or knowing man) in the family Hominidae (the great apes). ... Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than air does. ...

For instance the adult human heart consists of two separated pumps, the right side with the right atrium and ventricle (which pumps deoxygenated blood into the pulmonary circulation), and the left side with the left atrium and ventricle (which pumps oxygenated blood into the systemic circulation). Blood in one circuit has to go through the heart to enter the other circuit. The heart and lungs, from an older edition of Grays Anatomy. ... In anatomy, the atrium (plural: atria) is the blood collection chamber of a heart. ... In the heart, a ventricle is a heart chamber which collects blood from an atrium (another heart chamber that is smaller than a ventricle) and pumps it out of the heart. ...

Blood circulates through the body at speeds which vary by a factor of ten, from 1.2 m/s in the aorta to approximately 1.1 cm/s in the capillaries. 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 traveling the entire circulatory distance. The average heart pumps about 5,040 ml of blood per minute and an average adult has about 5 liters of total blood volume, so the heart is exchanging blood volume at a rate of about ten times per second.

See also

• Circulatory systems

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 (diastole). 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 doulble 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. Diagram of the human circulatory system. ...

The advantage of a double circulatory system is that blood can be pumped to the rest of the body at a higher pressure.