Circulatory system

The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.

The circulatory system includes the lymphatic system, which circulates lymph.[1] The passage of lymph for example takes much longer than that of blood.[2] Blood is a fluid consisting of plasma, red blood cells, white blood cells, and platelets that is circulated by the heart through the vertebrate vascular system, carrying oxygen and nutrients to and waste materials away from all body tissues. Lymph is essentially recycled excess blood plasma after it has been filtered from the interstitial fluid (between cells) and returned to the lymphatic system. The cardiovascular (from Latin words meaning "heart" and "vessel") system comprises the blood, heart, and blood vessels.[3] The lymph, lymph nodes, and lymph vessels form the lymphatic system, which returns filtered blood plasma from the interstitial fluid (between cells) as lymph.

The circulatory system of the blood is seen as having two components, a systemic circulation and a pulmonary circulation.[4]

While humans, as well as other vertebrates, have a closed cardiovascular system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have an open cardiovascular system. The lymphatic system, on the other hand, is an open system providing an accessory route for excess interstitial fluid to be returned to the blood.[5] The more primitive, diploblastic animal phyla lack circulatory systems.

Many diseases affect the circulatory system. This includes cardiovascular disease, affecting the cardiovascular system, and lymphatic disease affecting the lymphatic system. Cardiologists are medical professionals which specialise in the heart, and cardiothoracic surgeons specialise in operating on the heart and its surrounding areas. Vascular surgeons focus on other parts of the circulatory system.

Circulatory system
Circulatory System en
The human circulatory system (simplified). Red indicates oxygenated blood carried in arteries, blue indicates deoxygenated blood carried in veins. Capillaries, which join the arteries and veins, and the lymphatic vessels are not shown.
Anatomical terminology


Cardiovascular system

Vein art near
Depiction of the heart, major veins and arteries constructed from body scans.
Cross section of a human artery
Sankey diagram human circulatory system
Relative percentages of cardiac output delivered to major organ systems

The essential components of the human cardiovascular system are the heart, blood and blood vessels.[6] It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated; and the systemic circulation, a "loop" through the rest of the body to provide oxygenated blood. The systemic circulation can also be seen to function in two parts – a macrocirculation and a microcirculation. An average adult contains five to six quarts (roughly 4.7 to 5.7 liters) of blood, accounting for approximately 7% of their total body weight.[7] Blood consists of plasma, red blood cells, white blood cells, and platelets. Also, the digestive system works with the circulatory system to provide the nutrients the system needs to keep the heart pumping.[8]

The cardiovascular systems of humans are closed, meaning that the blood never leaves the network of blood vessels. In contrast, oxygen and nutrients diffuse across the blood vessel layers and enter interstitial fluid, which carries oxygen and nutrients to the target cells, and carbon dioxide and wastes in the opposite direction. The other component of the circulatory system, the lymphatic system, is open.


Oxygenated blood enters the systemic circulation when leaving the left ventricle, through the aortic semilunar valve. The first part of the systemic circulation is the aorta, a massive and thick-walled artery. The aorta arches and gives branches supplying the upper part of the body after passing through the aortic opening of the diaphragm at the level of thoracic ten vertebra, it enters the abdomen. Later it descends down and supplies branches to abdomen, pelvis, perineum and the lower limbs. The walls of aorta are elastic. This elasticity helps to maintain the blood pressure throughout the body. When the aorta receives almost five litres of blood from the heart, it recoils and is responsible for pulsating blood pressure. Moreover, as aorta branches into smaller arteries, their elasticity goes on decreasing and their compliance goes on increasing.


Arteries branch into small passages called arterioles and then into the capillaries.[9] The capillaries merge to bring blood into the venous system.[10]


After their passage through body tissues, capillaries merge once again into venules, which continue to merge into veins. The venous system finally coalesces into two major veins: the superior vena cava (roughly speaking draining the areas above the heart) and the inferior vena cava (roughly speaking from areas below the heart). These two great vessels empty into the right atrium of the heart.

Coronary vessels

The heart itself is supplied with oxygen and nutrients through a small "loop" of the systemic circulation and derives very little from the blood contained within the four chambers.

Portal veins

The general rule is that arteries from the heart branch out into capillaries, which collect into veins leading back to the heart. Portal veins are a slight exception to this. In humans the only significant example is the hepatic portal vein which combines from capillaries around the gastrointestinal tract where the blood absorbs the various products of digestion; rather than leading directly back to the heart, the hepatic portal vein branches into a second capillary system in the liver.


Diagram of the human heart (cropped)
View from the front

The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs. In the human heart there is one atrium and one 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. The right atrium is the upper chamber of the right side of the heart. The blood that is returned to the right atrium is deoxygenated (poor in oxygen) and passed into the right ventricle to be pumped through the pulmonary artery to the lungs for re-oxygenation and removal of carbon dioxide. The left atrium receives newly oxygenated blood from the lungs as well as the pulmonary vein which is passed into the strong left ventricle to be pumped through the aorta to the different organs of the body.

The coronary circulation system provides a blood supply to the heart muscle itself. The coronary circulation begins near the origin of the aorta by two coronary arteries: the right coronary artery and the left coronary artery. After nourishing the heart muscle, blood returns through the coronary veins into the coronary sinus and from this one into the right atrium. Back flow of blood through its opening during atrial systole is prevented by the Thebesian valve. The smallest cardiac veins drain directly into the heart chambers.[8]


2119 Pulmonary Circuit
The pulmonary circulation as it passes from the heart. Showing both the pulmonary and bronchial arteries.

The circulatory system of the lungs is the portion of the cardiovascular system in which oxygen-depleted blood is pumped away from the heart, via the pulmonary artery, to the lungs and returned, oxygenated, to the heart via the pulmonary vein.

Oxygen deprived blood from the superior and inferior vena cava enters the right atrium of the heart and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, from which it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. Gas exchange occurs in the lungs, whereby CO2 is released from the blood, and oxygen is absorbed. The pulmonary vein returns the now oxygen-rich blood to the left atrium.[8]

A separate system known as the bronchial circulation supplies blood to the tissue of the larger airways of the lung.

Systemic circulation

2101 Blood Flow Through the Heart
The systemic circulation and capillary networks shown and also as separate from the pulmonary circulation

Systemic circulation is the portion of the cardiovascular system which transports oxygenated blood away from the heart through the aorta from the left ventricle where the blood has been previously deposited from pulmonary circulation, to the rest of the body, and returns oxygen-depleted blood back to the heart.[8]


The brain has a dual blood supply that comes from arteries at its front and back. These are called the "anterior" and "posterior" circulation respectively. The anterior circulation arises from the internal carotid arteries and supplies the front of the brain. The posterior circulation arises from the vertebral arteries, and supplies the back of the brain and brainstem. The circulation from the front and the back join together (anastomise) at the Circle of Willis.


The renal circulation receives around 20% of the cardiac output. It branches from the abdominal aorta and returns blood to the ascending vena cava. It is the blood supply to the kidneys, and contains many specialized blood vessels.

Lymphatic system

The lymphatic system is part of the circulatory system. It is a network of lymphatic vessels and lymph capillaries, lymph nodes and organs, and lymphatic tissues and circulating lymph. One of its major functions is to carry the lymph, draining and returning interstitial fluid back towards the heart for return to the cardiovascular system, by emptying into the lymphatic ducts. Its other main function is in the adaptive immune system.[11]


The development of the circulatory system starts with vasculogenesis in the embryo. The human arterial and venous systems develop from different areas in the embryo. The arterial system develops mainly from the aortic arches, six pairs of arches which develop on the upper part of the embryo. The venous system arises from three bilateral veins during weeks 4 – 8 of embryogenesis. Fetal circulation begins within the 8th week of development. Fetal circulation does not include the lungs, which are bypassed via the truncus arteriosus. Before birth the fetus obtains oxygen (and nutrients) from the mother through the placenta and the umbilical cord.[12]


The human arterial system originates from the aortic arches and from the dorsal aortae starting from week 4 of embryonic life. The first and second aortic arches regress and forms only the maxillary arteries and stapedial arteries respectively. The arterial system itself arises from aortic arches 3, 4 and 6 (aortic arch 5 completely regresses).

The dorsal aortae, present on the dorsal side of the embryo, are initially present on both sides of the embryo. They later fuse to form the basis for the aorta itself. Approximately thirty smaller arteries branch from this at the back and sides. These branches form the intercostal arteries, arteries of the arms and legs, lumbar arteries and the lateral sacral arteries. Branches to the sides of the aorta will form the definitive renal, suprarenal and gonadal arteries. Finally, branches at the front of the aorta consist of the vitelline arteries and umbilical arteries. The vitelline arteries form the celiac, superior and inferior mesenteric arteries of the gastrointestinal tract. After birth, the umbilical arteries will form the internal iliac arteries.


The human venous system develops mainly from the vitelline veins, the umbilical veins and the cardinal veins, all of which empty into the sinus venosus.


Cardiovascular system

Erytrocyte deoxy to oxy v0.7
Animation of a typical human red blood cell cycle in the circulatory system. This animation occurs at a faster rate (~20 seconds of the average 60-second cycle) and shows the red blood cell deforming as it enters capillaries, as well as the bars changing color as the cell alternates in states of oxygenation along the circulatory system.

About 98.5% of the oxygen in a sample of arterial blood in a healthy human, breathing air at sea-level pressure, is chemically combined with hemoglobin molecules. About 1.5% is physically dissolved in the other blood liquids and not connected to hemoglobin. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species.

Lymphatic system

Clinical significance

Many diseases affect the circulatory system. These include a number of cardiovascular diseases, affecting the cardiovascular system, and lymphatic diseases affecting the lymphatic system. Cardiologists are medical professionals which specialise in the heart, and cardiothoracic surgeons specialise in operating on the heart and its surrounding areas. Vascular surgeons focus on other parts of the circulatory system.

Cardiovascular disease

Diseases affecting the cardiovascular system are called cardiovascular disease.

Many of these diseases are called "lifestyle diseases" because they develop over time and are related to a person's exercise habits, diet, whether they smoke, and other lifestyle choices a person makes. Atherosclerosis is the precursor to many of these diseases. It is where small atheromatous plaques build up in the walls of medium and large arteries. This may eventually grow or rupture to occlude the arteries. It is also a risk factor for acute coronary syndromes, which are diseases which are characterised by a sudden deficit of oxygenated blood to the heart tissue. Atherosclerosis is also associated with problems such as aneurysm formation or splitting ("dissection") of arteries.

Another major cardiovascular disease involves the creation of a clot, called a "thrombus". These can originate in veins or arteries. Deep venous thrombosis, which mostly occurs in the legs, is one cause of clots in the veins of the legs, particularly when a person has been stationary for a long time. These clots may embolise, meaning travel to another location in the body. The results of this may include pulmonary embolus, transient ischaemic attacks, or stroke.

Cardiovascular diseases may also be congenital in nature, such as heart defects or persistent fetal circulation, where the circulatory changes that are supposed to happen after birth do not. Not all congenital changes to the circulatory system are associated with diseases, a large number are anatomical variations.


The function and health of the circulatory system and its parts are measured in a variety of manual and automated ways. These include simple methods such as those that are part of the cardiovascular examination, including the taking of a person's pulse as an indicator of a person's heart rate, the taking of blood pressure through a sphygmomanometer or the use of a stethoscope to listen to the heart for murmurs which may indicate problems with the heart's valves. An electrocardiogram can also be used to evaluate the way in which electricity is conducted through the heart.

Other more invasive means can also be used. A cannula or catheter inserted into an artery may be used to measure pulse pressure or pulmonary wedge pressures. Angiography, which involves injecting a dye into an artery to visualise an arterial tree, can be used in the heart (coronary angiography) or brain. At the same time as the arteries are visualised, blockages or narrowings may be fixed through the insertion of stents, and active bleeds may be managed by the insertion of coils. An MRI may be used to image arteries, called an MRI angiogram. For evaluation of the blood supply to the lungs a CT pulmonary angiogram may be used.

Vascular ultrasonography include for example:


There are a number of surgical procedures performed on the circulatory system:

Cardiovascular procedures are more likely to be performed in an inpatient setting than in an ambulatory care setting; in the United States, only 28% of cardiovascular surgeries were performed in the ambulatory care setting.[13]

Other animals

While humans, as well as other vertebrates, have a closed cardiovascular system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have an open cardiovascular system. The lymphatic system, on the other hand, is an open system providing an accessory route for excess interstitial fluid to be returned to the blood.[5] The more primitive, diploblastic animal phyla lack circulatory systems.

The blood vascular system first appeared probably in an ancestor of the triploblasts over 600 million years ago, overcoming the time-distance constraints of diffusion, while endothelium evolved in an ancestral vertebrate some 540–510 million years ago.[14]

Open circulatory system

Open Circulatroy
The open circulatory system of the grasshopper – made up of a heart, vessels and hemolymph. The hemolymph is pumped through the heart, into the aorta, dispersed into the head and throughout the hemocoel, then back through the ostia in the heart and the process repeated.

In arthropods, the open circulatory system is a system in which a fluid 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.[15] Muscular movements by the animal during 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 cells. Hemolymph is composed of water, inorganic salts (mostly sodium, chloride, potassium, magnesium, and calcium), and organic compounds (mostly carbohydrates, proteins, and lipids). The primary oxygen transporter molecule is hemocyanin.

There are free-floating cells, the hemocytes, within the hemolymph. They play a role in the arthropod immune system.

Pseudoceros bifurcus - Blue Pseudoceros Flatworm
Flatworms, such as this Pseudoceros bifurcus, lack specialized circulatory organs

Closed circulatory system

Two chamber heart
Two-chambered heart of a fish

The circulatory systems of all vertebrates, as well as of annelids (for example, earthworms) and cephalopods (squids, octopuses and relatives) are closed, just as in humans. Still, the systems of fish, amphibians, reptiles, and birds show various stages of the evolution of the circulatory system.[16]

In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as single cycle 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.

In reptiles, the ventricular septum of the heart is incomplete and the pulmonary artery is equipped with a sphincter muscle. This allows a second possible route of blood flow. Instead of blood flowing through the pulmonary artery to the lungs, the sphincter may be contracted to divert this blood flow through the incomplete ventricular septum into the left ventricle and out through the aorta. This means the blood flows from the capillaries to the heart and back to the capillaries instead of to the lungs. This process is useful to ectothermic (cold-blooded) animals in the regulation of their body temperature.

Birds, mammals, and crocodilians 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 and crocodilians evolved independently from that of mammals.[17]

No circulatory system

Circulatory systems are absent in some animals, including flatworms. 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.

Some animals, such as jellyfish, have more extensive branching from their gastrovascular cavity (which functions as both a place of digestion and a form of circulation), this branching allows for bodily fluids to reach the outer layers, since the digestion begins in the inner layers.


Charta ex qva figvram parare convenit, illi qvae nervorvm seriem exprimit appendendam, 1543.
Human anatomical chart of blood vessels, with heart, lungs, liver and kidneys included. Other organs are numbered and arranged around it. Before cutting out the figures on this page, Vesalius suggests that readers glue the page onto parchment and gives instructions on how to assemble the pieces and paste the multilayered figure onto a base "muscle man" illustration. "Epitome", fol.14a. HMD Collection, WZ 240 V575dhZ 1543.

The earliest known writings on the circulatory system are found in the Ebers Papyrus (16th century BCE), an ancient Egyptian medical papyrus containing over 700 prescriptions and remedies, both physical and spiritual. In the papyrus, it acknowledges the connection of the heart to the arteries. The Egyptians thought air came in through the mouth and into the lungs and heart. From the heart, the air travelled to every member through the arteries. Although this concept of the circulatory system is only partially correct, it represents one of the earliest accounts of scientific thought.

In the 6th century BCE, the knowledge of circulation of vital fluids through the body was known to the Ayurvedic physician Sushruta in ancient India.[18] He also seems to have possessed knowledge of the arteries, described as 'channels' by Dwivedi & Dwivedi (2007).[18] The valves of the heart were discovered by a physician of the Hippocratean school around the 4th century BCE. 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.

The Greek physician, Herophilus, distinguished veins from arteries but thought that the pulse was a property of arteries themselves. Greek anatomist 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.[19]

In 2nd century AD Rome, the 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 1025, The Canon of Medicine by the Persian physician, Avicenna, "erroneously accepted the Greek notion regarding the existence of a hole in the ventricular septum by which the blood traveled between the ventricles." Despite this, Avicenna "correctly wrote on the cardiac cycles and valvular function", and "had a vision of blood circulation" in his Treatise on Pulse.[20] While also refining Galen's erroneous theory of the pulse, Avicenna provided the first correct explanation of pulsation: "Every beat of the pulse comprises two movements and two pauses. Thus, expansion : pause : contraction : pause. [...] The pulse is a movement in the heart and arteries ... which takes the form of alternate expansion and contraction."[21]

In 1242, the Arabian physician, Ibn al-Nafis, became the first person to accurately describe the process of pulmonary circulation, for which he is sometimes considered the father of circulatory physiology.[22] Ibn al-Nafis stated in his Commentary on Anatomy in Avicenna's Canon:

"...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..."

In addition, Ibn al-Nafis had an insight into what would become a larger theory of the capillary circulation. He stated that "there must be small communications or pores (manafidh in Arabic) between the pulmonary artery and vein," a prediction that preceded the discovery of the capillary system by more than 400 years.[23] Ibn al-Nafis' theory, however, was confined to blood transit in the lungs and did not extend to the entire body.

Michael Servetus was the first European to describe the function of pulmonary circulation, although his achievement was not widely recognized at the time, for a few reasons. He firstly described it in the "Manuscript of Paris"[24][25] (near 1546), but this work was never published. And later he published this description, but in a theological treatise, Christianismi Restitutio, not in a book on medicine. Only three copies of the book survived but these remained hidden for decades, the rest were burned shortly after its publication in 1553 because of persecution of Servetus by religious authorities.

Better known discovery of pulmonary circulation was by Vesalius's successor at Padua, Realdo Colombo, in 1559.

William Harvey (1578-1657) Venenbild
Image of veins from William Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, 1628

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 published Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus in 1628, which "demonstrated that there had to be a direct connection between the venous and arterial systems throughout the body, and not just the lungs. Most importantly, he argued that the beat of the heart produced a continuous circulation of blood through minute connections at the extremities of the body. This is a conceptual leap that was quite different from Ibn al-Nafis' refinement of the anatomy and bloodflow in the heart and lungs."[26] This work, with its essentially correct exposition, slowly convinced the medical world. However, Harvey was not able to identify the capillary system connecting arteries and veins; these were later discovered by Marcello Malpighi in 1661.

In 1956, André Frédéric Cournand, Werner Forssmann and Dickinson W. Richards were awarded the Nobel Prize in Medicine "for their discoveries concerning heart catheterization and pathological changes in the circulatory system."[27] In his Nobel lecture, Forssmann credits Harvey as birthing cardiology with the publication of his book in 1628.[28]

In the 1970s, Diana McSherry developed computer-based systems to create images of the circulatory system and heart without the need for surgery.[29]

See also


  1. ^ "circulatory system" at Dorland's Medical Dictionary
  2. ^ "Let's beat cancer sooner". Cancer Research UK. Retrieved April 13, 2017.
  3. ^ "cardiovascular system" at Dorland's Medical Dictionary
  4. ^ "How does the blood circulatory system work?". PubMed Health. 1 August 2016.
  5. ^ a b Sherwood, Lauralee (2011). Human Physiology: From Cells to Systems. Cengage Learning. pp. 401–. ISBN 978-1-133-10893-1.
  6. ^ Cardiovascular+System at the US National Library of Medicine Medical Subject Headings (MeSH)
  7. ^ Pratt, Rebecca. "Cardiovascular System: Blood". AnatomyOne. Amirsys, Inc. Archived from the original on 2017-02-24.
  8. ^ a b c d Guyton, Arthur; Hall, John (2000). Guyton Textbook of Medical Physiology (10 ed.). ISBN 978-0-7216-8677-6.
  9. ^ National Institutes of Health. "What Are the Lungs?". Archived from the original on 2014-10-04.
  10. ^ State University of New York (February 3, 2014). "The Circulatory System". Archived from the original on February 3, 2014.
  11. ^ Alberts, B.; Johnson, A.; Lewis, J.; Raff, M.; Roberts, K.; Walters, P. (2002). Molecular Biology of the Cell (4th ed.). New York and London: Garland Science. ISBN 978-0-8153-3218-3.
  12. ^ Whitaker, Kent (2001). "Fetal Circulation". Comprehensive Perinatal and Pediatric Respiratory Care. Delmar Thomson Learning. pp. 18–20. ISBN 978-0-7668-1373-1.
  13. ^ Wier LM, Steiner CA, Owens PL (April 17, 2015). "Surgeries in Hospital-Owned Outpatient Facilities, 2012". HCUP Statistical Brief #188. Rockville, MD: Agency for Healthcare Research and Quality.
  14. ^ Monahan‐Earley, R., Dvorak, A.M., & Aird, W.C. (2013). Evolutionary origins of the blood vascular system and endothelium. Journal of Thrombosis and Haemostasis 11 (s1): 46–66.
  15. ^ Bailey, Regina. "Circulatory System".
  16. ^ Simões-Costa MS, et al. 2005. The evolutionary origin of cardiac chambers. Dev. Biol. 277: 1–15.
  17. ^ "Crocodilian Hearts". National Center for Science Education. October 24, 2008. Retrieved October 3, 2015.
  18. ^ a b Dwivedi, Girish & Dwivedi, Shridhar (2007). "History of Medicine: Sushruta – the Clinician – Teacher par Excellence" Archived October 10, 2008, at the Wayback Machine, Indian J Chest Dis Allied Sci Vol. 49 pp. 243–244, National Informatics Centre (Government of India).
  19. ^ Anatomy – History of anatomy. Retrieved 2013-09-15.
  20. ^ Shoja, M.M.; Tubbs, R.S.; Loukas, M.; Khalili, M.; Alakbarli, F.; Cohen-Gadol, A.A. (2009). "Vasovagal syncope in the Canon of Avicenna: The first mention of carotid artery hypersensitivity". International Journal of Cardiology. 134 (3): 297–301. doi:10.1016/j.ijcard.2009.02.035. PMID 19332359.
  21. ^ Hajar, Rachel (1999). "The Greco-Islamic Pulse". Heart Views. 1 (4): 136–140 [138]. Archived from the original on 2014-01-09.
  22. ^ Reflections, Chairman's (2004). "Traditional Medicine Among Gulf Arabs, Part II: Blood-letting". Heart Views. 5 (2): 74–85 [80]. Archived from the original on 2007-09-11.
  23. ^ West, J.B. (2008). "Ibn al-Nafis, the pulmonary circulation, and the Islamic Golden Age". Journal of Applied Physiology. 105 (6): 1877–1880. doi:10.1152/japplphysiol.91171.2008. PMC 2612469. PMID 18845773.
  24. ^ Gonzalez Etxeberria, Patxi (2011) Amor a la verdad, el – vida y obra de Miguel servet [The love for truth. Life and work of Michael Servetus]. Navarro y Navarro, Zaragoza, collaboration with the Government of Navarra, Department of Institutional Relations and Education of the Government of Navarra. ISBN 84-235-3266-6 pp. 215–228 & 62nd illustration (XLVII)
  25. ^ Michael Servetus Research Study with graphical proof on the Manuscript of Paris and many other manuscripts and new works by Servetus
  26. ^ Pormann, Peter E. and Smith, E. Savage (2007) Medieval Islamic medicine Georgetown University, Washington DC, p. 48, ISBN 1-58901-161-9.
  27. ^ "The Nobel Prize in Physiology or Medicine 1956". Nobel Foundation. Retrieved 2007-07-28.
  28. ^ "The Role of Heart Catheterization and Angiocardiography in the Development of Modern Medicine". Retrieved 2017-10-08.
  29. ^ Wayne, Tiffany K. (2011). American women of science since 1900. Santa Barbara, Calif.: ABC-CLIO. pp. 677–678. ISBN 978-1-59884-158-9.

External links


Angiology (from Greek ἀγγεῖον, angeīon, "vessel"; and -λογία, -logia) is the medical specialty which studies the diseases of the circulatory system and of the lymphatic system, i.e., arteries, veins and lymphatic vessels, and its diseases.

In the UK, this field is more often termed angiology, and in the United States the term vascular medicine is more frequent. The field of vascular medicine (angiology) is the field that deals with preventing, diagnosing and treating vascular and blood vessel related diseases.


An artery (plural arteries) (from Greek, Modern ἀρτηρία (artēria), meaning 'windpipe, artery') is a blood vessel that takes blood away from the heart to all parts of the body (tissues, lungs, etc). Most arteries carry oxygenated blood; the two exceptions are the pulmonary and the umbilical arteries, which carry deoxygenated blood to the organs that oxygenate it. The effective arterial blood volume is that extracellular fluid which fills the arterial system.

The arteries are part of the circulatory system, which is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, the maintenance of optimum blood pH, and the circulation of proteins and cells of the immune system. In developed countries, the two leading causes of death, myocardial infarction (heart attack), and stroke, may each directly result from an arterial system that has been slowly and progressively compromised by years of deterioration (usually clogged by cholesterol).

Blood vessel

The blood vessels are the part of the circulatory system, and microcirculation, that transports blood throughout the human body. These vessels are designed to transport nutrients and oxygen to the tissues of the body. They also take waste and carbon dioxide and carry them away from the tissues and back to the heart. Blood vessels are needed to sustain life as all of the body’s tissues rely on their functionality.There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart. The word vascular, meaning relating to the blood vessels, is derived from the Latin vas, meaning vessel. Some structures -- such as cartilage, the epithelium, and the lens and cornea of the eye -- do not contain blood vessels and are labeled avascular.

Cardiovascular physiology

Cardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular").

These subjects are sometimes addressed separately, under the names cardiac physiology and circulatory physiology.Although the different aspects of cardiovascular physiology are closely interrelated, the subject is still usually divided into several subtopics.

Circulatory System (band)

Circulatory System is a psychedelic rock musical ensemble formed by musician/painter Will Cullen Hart, and featuring Derek Almstead, Suzanne Allison, Peter Erchick, John Fernandes, Charlie Johnston, and Heather McIntosh.

Hart, part of the Elephant Six Collective, was one of the lead players in The Olivia Tremor Control. After that group disbanded in 2000, he and most of the other former Olivias, with the exception of Bill Doss (who was focusing on his solo project Sunshine Fix), and Eric Harris, formed Circulatory System. Neutral Milk Hotel's Jeff Mangum also contributed to their albums, but was only briefly part of the touring version of the band.

Their third full-length album, Mosaics within Mosaics, was released on June 24, 2014.

Circulatory system of gastropods

As in other molluscs, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in colour.

Endocrine system

The endocrine system is a chemical messenger system consisting of hormones, the group of glands of an organism that secrete those hormones directly into the circulatory system to regulate the function of distant target organs, and the feedback loops which modulate hormone release so that homeostasis is maintained. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. The study of the endocrine system and its disorders is known as endocrinology. Endocrinology is a branch of internal medicine.Special features of endocrine glands are, in general, their ductless nature, their vascularity, and commonly the presence of intracellular vacuoles or granules that store their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen. A number of glands that signal each other in sequence are usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.

In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems, such as bone, kidney, liver, heart and gonads, have secondary endocrine functions. For example, the kidney secretes endocrine hormones such as erythropoietin and renin. Hormones can consist of either amino acid complexes, steroids, eicosanoids, leukotrienes, or prostaglandins.The endocrine system is in contrast to the exocrine system, which secretes its hormones to the outside of the body using ducts. As opposed to endocrine factors that travel considerably longer distances via the circulatory system, other signaling molecules, such as paracrine factors involved in paracrine signalling diffuse over a relatively short distance.

The word endocrine derives via New Latin from the Greek words ἔνδον, endon, "inside, within," and "crine" from the κρίνω, krīnō, "to separate, distinguish".

Fetal circulation

In animals that give live birth, the fetal circulation is the circulatory system of a fetus. The term usually encompasses the entire fetoplacental circulation, which includes the umbilical cord and the blood vessels within the placenta that carry fetal blood.

The fetal (prenatal) circulation works differently from normal postnatal circulation, mainly because the lungs are not in use. Instead, the fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord. The advent of breathing and the severance of the umbilical cord prompt various neuroendocrine changes that shortly transform fetal circulation into postnatal circulation.

The fetal circulation of humans has been extensively studied by the health sciences. Much is known also of fetal circulation in other animals, especially livestock and model organisms such as mice, through the health sciences, veterinary science, and life sciences generally.


Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod body remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph cells called hemocytes are suspended. In addition to hemocytes, the plasma also contains many chemicals. It is the major tissue type of the open circulatory system characteristic of arthropods (e.g. arachnids, crustaceans and insects). In addition, some non-arthropods such as molluscs possess a hemolymphatic circulatory system.


A hormone (from the Greek participle “ὁρμῶ”, "to arouse") is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behavior. Hormones have diverse chemical structures, mainly of three classes: eicosanoids, steroids, and amino acid/protein derivatives (amines, peptides, and proteins). The glands that secrete hormones comprise the endocrine signaling system. The term hormone is sometimes extended to include chemicals produced by cells that affect the same cell (autocrine or intracrine signalling) or nearby cells (paracrine signalling).

Hormones are used to communicate between organs and tissues for physiological regulation and behavioral activities, such as digestion, metabolism, respiration, tissue function, sensory perception, sleep, excretion, lactation, stress, growth and development, movement, reproduction, and mood. Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a signal transduction pathway that typically activates gene transcription resulting in increased expression of target proteins; non-genomic effects are more rapid, and can be synergistic with genomic effects. Amino acid–based hormones (amines and peptide or protein hormones) are water-soluble and act on the surface of target cells via second messengers; steroid hormones, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei.

Hormone secretion may occur in many tissues. Endocrine glands are the cardinal example, but specialized cells in various other organs also secrete hormones. Hormone secretion occurs in response to specific biochemical signals from a wide range of regulatory systems. For instance, serum calcium concentration affects parathyroid hormone synthesis; blood sugar (serum glucose concentration) affects insulin synthesis; and because the outputs of the stomach and exocrine pancreas (the amounts of gastric juice and pancreatic juice) become the input of the small intestine, the small intestine secretes hormones to stimulate or inhibit the stomach and pancreas based on how busy it is. Regulation of hormone synthesis of gonadal hormones, adrenocortical hormones, and thyroid hormones is often dependent on complex sets of direct influence and feedback interactions involving the hypothalamic-pituitary-adrenal (HPA), -gonadal (HPG), and -thyroid (HPT) axes.

Upon secretion, certain hormones, including protein hormones and catecholamines, are water-soluble and are thus readily transported through the circulatory system. Other hormones, including steroid and thyroid hormones, are lipid-soluble; to allow for their widespread distribution, these hormones must bond to carrier plasma glycoproteins (e.g., thyroxine-binding globulin (TBG)) to form ligand-protein complexes. Some hormones are completely active when released into the bloodstream (as is the case for insulin and growth hormones), while others are prohormones that must be activated in specific cells through a series of activation steps that are commonly highly regulated. The endocrine system secretes hormones directly into the bloodstream, typically via fenestrated capillaries, whereas the exocrine system secretes its hormones indirectly using ducts. Hormones with paracrine function diffuse through the interstitial spaces to nearby target tissue.


Levocardia is a medical condition where the heart is on the normal side of the body (the left), as opposed to dextrocardia, in which the heart is in the right side of the thoracic cavity. This can be associated with situs solitus, where the remainder of the organs are on normal side as well; or situs inversus, in which the viscera (stomach, liver, intestines, lungs, etc.) on the opposite side as normal. The latter condition may or may not be associated with clinically relevant abnormalities.

List of ICD-9 codes

The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems .

List of ICD-9 codes 001–139: infectious and parasitic diseases

List of ICD-9 codes 140–239: neoplasms

List of ICD-9 codes 240–279: endocrine, nutritional and metabolic diseases, and immunity disorders

List of ICD-9 codes 280–289: diseases of the blood and blood-forming organs

List of ICD-9 codes 290–319: mental disorders

List of ICD-9 codes 320–389: diseases of the nervous system and sense organs

List of ICD-9 codes 390–459: diseases of the circulatory system

List of ICD-9 codes 460–519: diseases of the respiratory system

List of ICD-9 codes 520–579: diseases of the digestive system

List of ICD-9 codes 580–629: diseases of the genitourinary system

List of ICD-9 codes 630–679: complications of pregnancy, childbirth, and the puerperium

List of ICD-9 codes 680–709: diseases of the skin and subcutaneous tissue

List of ICD-9 codes 710–739: diseases of the musculoskeletal system and connective tissue

List of ICD-9 codes 740–759: congenital anomalies

List of ICD-9 codes 760–779: certain conditions originating in the perinatal period

List of ICD-9 codes 780–799: symptoms, signs, and ill-defined conditions

List of ICD-9 codes 800–999: injury and poisoning

List of ICD-9 codes E and V codes: external causes of injury and supplemental classification

List of organs of the human body

This article contains a list of organs of the human body. It is widely believed that there are 79 organs; however, there is no universally standard definition of what constitution an organ, and some tissue groups' status as one is debated. Since there is no single standard definition of what an organ is, the number of organs varies depending on how one defines an organ. For example, this list contains much more than 79 different organs.

Organ system

An organ system is a group of organs that work together as a biological system to perform one or more functions. Each organ system does a particular job in the body, and is made up of certain tissues.

Side 3 (Circulatory System album)

Side 3 (2010) is a remix, demos and alternate-takes album of Circulatory System's 2009 release Signal Morning.

The limited release 12" album came with the deluxe package of Signal Morning.

The covers for the album were handmade and individually stencil spray-painted with the number 3, on top of the original Signal Morning album cover. The inlay has the words "Circulatory System" stenciled. It was released in various colors and variations of layout, designed by Will Cullen Hart.

Will Cullen Hart

William "Will" Cullen Hart (born June 14, 1971) is an American pop musician and painter. He was a co-founder of The Elephant 6 Recording Company, as well as the rock band The Olivia Tremor Control. Following that band's breakup, Hart and several other former members regrouped to create Circulatory System.

Hart grew up in Ruston, Louisiana, with Bill Doss, Jeff Mangum and Robert Schneider. Doss and Hart (and, early on, Mangum) combined their musical efforts in The Olivia Tremor Control. Hart and Doss blended their differing musical inclinations for the band: Hart being known as the sonic experimenter, Doss the proponent of pop. This difference is evidently clear in the music produced by each since the end of the Olivia Tremor Control. Hart's Circulatory System maintains an interest in experimentation, while Doss' Sunshine Fix focused on more traditionally structured Beatlesque pop.

Will Cullen Hart is also a visual artist. He has created most, if not all of the artwork for the Olivia Tremor Control and Circulatory System (among other Elephant 6 bands), as well as individual pieces.

In a 2008 online interview with John Fernandes, it was revealed that Hart has been diagnosed with multiple sclerosis.

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