circulation

View more Health videos

(click to enlarge)
Human circulatory system. Oxygen-rich blood is shown in red, oxygen-poor blood in blue. The (credit: © Merriam-Webster Inc.)

Process by which nutrients, respiratory gases, and metabolic products are transported throughout the body. In humans, blood remains within a closed cardiovascular system composed of the heart, blood vessels, and blood. Arteries carry blood away from the heart under high pressure exerted by the heart's pumping action. Arteries divide into smaller arterioles, which branch into a network of tiny capillaries with thin walls across which gases and nutrients diffuse. Capillaries rejoin into larger venules, which unite to form veins, which carry blood back to the heart. ( artery; capillary; vein.) The right and left heart chambers send blood into separate pulmonary and systemic circulations. In the first, blood is carried from the heart to the lungs, where it picks up oxygen and releases carbon dioxide; in the second, blood is carried between the heart and the rest of the body, where it carries oxygen, nutrients, metabolic products, and wastes.

For more information on circulation, visit Britannica.com.

Those processes by which metabolic materials are transported from one region of an organism to another. Ultimately, the essential gases, nutrients, and waste products of metabolism are exchanged across cell membranes by diffusion. Diffusion is the movement of material, by random motion of molecules, from a region of high concentration to one of low concentration. The amount of material moved from one place to another depends on the difference in concentrations and on the distance between the two points. The greater the distance, the less movement of material per unit time for a given difference in concentration. Consequently, in all but the smallest animals, convection (or bulk circulation) of materials to the cell must be employed to supplement diffusion.

Protoplasmic movement aids diffusion at the intracellular level. In multicellular animals, however, either the external medium or extracellular body fluids, or both, are circulated. In sponges and coelenterates, water is pumped through definite body channels by muscular activity or, more often, by cilia or flagella on the cells lining the channels.

Coelenterates have a body wall derived from two cell layers; an outer ectoderm is separated from an inner endoderm by a noncellular gelatinous material (mesoglea). All higher animals have bodies consisting of three cell layers, with the ectoderm being separated from the endoderm by a cellular layer of mesoderm. The mesoderm proliferates and separates to develop a fluid-filled body cavity or coelom. The coelom separates the ectoderm (together with an outer layer of mesoderm) from the endoderm (which has an inner layer of mesoderm). Coelomic fluid is moved around by body movements or ciliary activity, but in larger animals this movement is usually inadequate to supply the metabolic requirements of the organs contained within the coelom. These needs are provided for by pumping a fluid, blood, to them through vessels, the blood vascular system. See also Blood.

When the blood is in a separate compartment from the rest of the extracellular fluid, the vascular system is described as closed. The two principal components of such systems are hearts and blood vessels. In such a system, the blood is circulated by a pump, the heart, through special channels, blood vessels; it comes into close association with the tissues only in the capillaries, fine vessels with walls only one cell thick. In some tissues or regions, larger blood spaces may exist, called sinuses. A closed vascular system is found in most annelids (segmented worms and leeches), cephalopod mollusks (squids and octopods), holothurian echinoderms (sea cucumbers), and vertebrates. See also Blood vessels; Heart (vertebrate).

In vertebrates, a functional but anatomically closed connection exists between the extracellular spaces (between the cells) and the blood vascular system in the form of lymph channels. Lymph is derived from the noncellular component of blood (plasma), modified in its passage through the tissues, and is conducted to the veins by blind-ending lymphatic vessels, which are separate from blood vessels and coelomic space. See also Lymphatic system.

In most arthropods (crustaceans, insects), most mollusks (shellfish), and many ascidians (sea squirts), the extracellular spaces are confluent with the blood system. In these animals, blood is pumped through a limited network of vessels into a body cavity called a hemocoel. After bathing the tissues, blood (called hemolymph in these organisms) collects in sinuses and returns to the heart. This is the open vascular system. In animals with open circulatory systems, the coelom is much reduced.

Readership of a periodical or other printed advertising medium. Since the cost of advertising in a periodical is based upon the number of readers deemed to be of interest to advertisers, the periodical's circulation is of prime concern. consumer magazines base advertising rates on paid circulation; trade magazines base advertising rates on the number of readers with the demographic characteristics of the periodical's target audience. The circulation claims of publishers are audited by the audit bureau of circulations, the Verified Audit of Circulation Corporation, or by the business publications audit of circulations. Total circulation counts sometimes include pass-along circulations.

The following are some specialized terms regarding circulation:

1. Bulk circulation-distribution of a publication by bundles as distinguished from distribution by individual pieces. For example: Schools will often subscribe to a local newspaper in bulk to be distributed to students and used as a tool in the classroom. This is considered part of the bulk circulation of the newspaper.

2. controlled circulation-copies of a periodical distributed free of charge to readers of interest to the advertisers; also called qualified circulation or nonpaid circulation. The Business Publications Audit of Circulations has specific rules for qualifying the readers as being part of the advertiser's target market. Generally, the reader must be in a particular industry or profession to qualify. For example, Circulation Management magazine readers must work in publishing or a related field.

3. Effective circulation-readership of a publication that is part of the advertiser's target market.

4. Franchise circulation-readership of a periodical obtained by sending copies free of charge to the customers of a business

organization.

5. paid circulation-total copies sold of a periodical consisting of net paid subscription copies and single copy sales. Paid circulation is usually calculated on an issue-by-issue basis or as an average over a six-month audit period. See also abc statement; average paid circulation.

6. Request circulation-recipients of a periodical that is sent free of charge upon request. According to Audit Bureau of Circulations rules, recipients must be part of the advertiser's target market to be counted as qualified circulation. According to Business Publications Audit of Circulations rules, recipients must have completed a request form that also includes survey questions qualifying the recipient as being of interest to the advertiser. See also bonus circulation; free circulation.

noun

1. Circular movement around a point or about an axis: circuit, circumvolution, gyration, revolution, rotation, turn, wheel, whirl. See geometry, repetition.
2. The passing out or spreading about of something: dispersal, dispersion, dissemination, distribution. See collect/distribute.

Definition: moving circularly
Antonyms: blockage

1. The movement of capital, labour, goods, and services throughout the economy.

2. More specifically, in population geography, short-term, repetitive movements of individuals, where there is no intention to change residence permanently. For example, many West African men move to cities after harvesting their crops. Employment opportunities are greater there, but the workers return to the land before the rains to plough, plant, and weed their crops. Other examples include the movement of students between term and vacation, movements between first and second homes, and commuting. see mobility.

3. The movements of air masses, or ocean currents.

1. The traffic pattern through an area or building.
2. In a building, a scheme providing for a smooth, economical, and functional flow of traffic.
3. A means of travel through a building, such as doors, corridors, stairs, and elevators.
4. The continuous flow of a liquid or gas within a closed circuit.

1. The flow or motion of a fluid in or through a given system.

2. The flow or motion of blood through the blood vessels.

LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!

The movement of blood through blood vessels.

• Journalism - circulation: publication’s readership and subscribers
• Money, Currency, and Denominations - circulation: paper currency and coins passed from person to person

Look up circulation in Wiktionary, the free dictionary.

Circulation may refer to:

• Circulatory system, a biological organ system whose primary function is to move substances to and from cells
• Circulation (fluid dynamics), the path integral of the fluid velocity around a closed curve
• Circulation (journal), one of the journals published by American Heart Association
• Circulation (architecture), the flow of people through a building
• Exhaust gas recirculation, a nitrogen oxide reduction technique used in most gasoline and diesel engines
• Atmospheric circulation, the large-scale movement of air
• Newspaper circulation, the average number of copies of a newspaper distributed on a day
• Magazine circulation, the average number of copies of a periodical distributed per edition/ volume
• Circulation (UK duo), a UK house music duo
• Circulation problem, a generalization of network flow problems
• Library circulation, the activities around the lending of library books and other material to users of a lending library
• Circulation (currency), all currency held by consumers and businesses, but not by financial institutions and governments
• Circulation Festival, an annual circus and fire performance festival held in Dunedin, New Zealand

See also

• List of circulating currencies

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - cirkulation, omløb, omsætning

idioms:

• be in circulation    færdes blandt folk
• out of circulation    ud af cirkulation

Nederlands (Dutch)
oplage, roulatie, (bloeds) omloop, betaalmiddelen, doorbloeding

Français (French)
n. - circulation, tirage, diffusion, à transmettre (document), usage, dans le circuit

idioms:

• in circulation    en circulation (de la monnaie), (fig) être dans le circuit
• out of circulation    hors circulation, hors circuit

Deutsch (German)
n. - Umlauf, Zirkulation, Kreislauf, Durchblutung, Verkehrsfluß, (verkaufte) Auflage

idioms:

• in circulation    im Umlauf sein, kursieren
• out of circulation    (ugs.) aus dem Verkehr gezogen

Ελληνική (Greek)
n. - κυκλοφορία, διανομή, διακίνηση

idioms:

• be in circulation    βρίσκομαι σε ενεργό δράση
• out of circulation    εκτός κυκλοφορίας

Italiano (Italian)
tiratura, circolazione, circolazione sanguigna

idioms:

• be in circulation    circolare
• out of circulation    fuori circolazione

Português (Portuguese)
n. - circulação (f), tiragem (f)

idioms:

• be in circulation    estar em circulação
• out of circulation    fora de circulação

Русский (Russian)
тираж, кровообращение, циркуляция

idioms:

• be in circulation    находиться в обращении
• out of circulation    быть изъятым из обращения

Español (Spanish)
n. - tirada, circulación de la sangre, circulación

idioms:

• in circulation    estar en circulación, en uso, estar activo social o comercialmente
• out of circulation    fuera de circulación

Svenska (Swedish)
n. - cirkulation, avsättning, betalningsmedel

中文（简体）(Chinese (Simplified))
流通, 发行量, 循环

idioms:

• be in circulation    传播, 流通
• out of circulation    停止流通, 不在活动

中文（繁體）(Chinese (Traditional))
n. - 流通, 發行量, 循環

idioms:

• be in circulation    傳播, 流通
• out of circulation    停止流通, 不在活動

한국어 (Korean)
n. - 순환 , 유통, 발행 부수

idioms:

• be in circulation    유포 또는 유통되고 있다

日本語 (Japanese)
n. - 循環, 流通, 流布, 通貨, 普及高, 貸出し

idioms:

• be in circulation    流布している
• out of circulation    流通していない, 活動していない

العربيه (Arabic)
‏(الاسم) توزيع, دوران, تداول‏

עברית (Hebrew)
n. - ‮הפצה, תפוצה, הסתובבות, מחזור, מחזור-הדם‬

If you are unable to view some languages clearly, click here.