The circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate.[1][2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia meaning heart, and from Latin vascula meaning vessels). The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit.[3] Some sources use the terms cardiovascular system and vascular system interchangeably with circulatory system.[4]
In vertebrates, the lymphatic system is complementary to the circulatory system. The lymphatic system carries excess plasma (filtered from the circulatory system capillaries as interstitial fluid between cells) away from the body tissues via accessory routes that return excess fluid back to blood circulation as lymph.[5] The lymphatic system is a subsystem that is essential for the functioning of the blood circulatory system; without it the blood would become depleted of fluid.
The lymphatic system also works with the immune system.[6] The circulation of lymph takes much longer than that of blood[7] and, unlike the closed (blood) circulatory system, the lymphatic system is an open system. Some sources describe it as a secondary circulatory system.
The circulatory system can be affected by many cardiovascular diseases. 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 disorders of the blood vessels, and lymphatic vessels.
Structure
Blood flow in the pulmonary and systemic circulations showing capillary networks in the torso sections
The circulatory system includes the heart, blood vessels, and blood.[2] The cardiovascular system in all vertebrates, consists of the heart and blood vessels. The circulatory system is further divided into two major circuits – a pulmonary circulation, and a systemic circulation.[8][1][3] The pulmonary circulation is a circuit loop from the right heart taking deoxygenated blood to the lungs where it is oxygenated and returned to the left heart. The systemic circulation is a circuit loop that delivers oxygenated blood from the left heart to the rest of the body, and returns deoxygenated blood back to the right heart via large veins known as the venae cavae. The systemic circulation can also be defined as 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.[9] Blood consists of plasma, red blood cells, white blood cells, and platelets. The digestive system also works with the circulatory system to provide the nutrients the system needs to keep the heart pumping.[10]
Diagram of the human heart showing blood oxygenation to the pulmonary and systemic circulation
The heart pumps blood to all parts of the body providing nutrients and oxygen to every cell, and removing waste products. The left heart pumps oxygenated blood returned from the lungs to the rest of the body in the systemic circulation. The right heart pumps deoxygenated blood to the lungs in the pulmonary circulation. 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 pulmonary circulation is the part of the circulatory 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.[10]
A separate circuit from the systemic circulation, the bronchial circulation supplies blood to the tissue of the larger airways of the lung.
Systemic circulation
Capillary bedDiagram of capillary network joining the arterial system with the venous system
The systemic circulation is a circuit loop that delivers oxygenated blood from the left heart to the rest of the body through the aorta. Deoxygenated blood is returned in the systemic circulation to the right heart via two large veins, the inferior vena cava and superior vena cava, where it is pumped from the right atrium into the pulmonary circulation for oxygenation. The systemic circulation can also be defined as having two parts – a macrocirculation and a microcirculation.[10]
Depiction of the heart, major veins and arteries constructed from body scans
Oxygenated blood enters the systemic circulation when leaving the left ventricle, via the aortic semilunar valve.[15] 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.[16] Later, it descends down and supplies branches to abdomen, pelvis, perineum and the lower limbs.[17]
The walls of the aorta are elastic. This elasticity helps to maintain the blood pressure throughout the body.[18] When the aorta receives almost five litres of blood from the heart, it recoils and is responsible for pulsating blood pressure. As the aorta branches into smaller arteries, their elasticity goes on decreasing and their compliance goes on increasing.[18]
Capillaries
Arteries branch into small passages called arterioles and then into the capillaries.[19] The capillaries merge to bring blood into the venous system.[20] The total length of muscle capillaries in a 70 kg human is estimated to be between 9,000 and 19,000 km.[21]
Capillaries merge into venules, which merge into veins.[22] The venous system feeds into the two major veins: the superior vena cava – which mainly drains tissues above the heart – and the inferior vena cava – which mainly drains tissues below the heart. These two large veins empty into the right atrium of the heart.[23]
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.
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. 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. Backflow of blood through its opening during atrial systole is prevented by the Thebesian valve. The smallest cardiac veins drain directly into the heart chambers.[10]
The brain has a dual blood supply, an anterior and a posterior circulation from arteries at its front and back. The anterior circulation arises from the internal carotid arteries to supply the front of the brain. The posterior circulation arises from the vertebral arteries, to supply the back of the brain and brainstem. The circulation from the front and the back join (anastomise) at the circle of Willis. The neurovascular unit, composed of various cells and vasculature channels within the brain, regulates the flow of blood to activated neurons in order to satisfy their high energy demands.[24]
Renal circulation
The renal circulation is the blood supply to the kidneys, contains many specialized blood vessels and receives around 20% of the cardiac output. It branches from the abdominal aorta and returns blood to the ascending inferior vena cava.
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 that 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.[25]
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.
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 form 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.
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 vertebrates.
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 that 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.
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.[26]
Other animals
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.
While humans, as well as other vertebrates, have a closed blood circulatory system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have an open circulatory system containing a heart but limited blood vessels. The most primitive, diploblastic animal phyla lack circulatory systems.
An additional transport system, the lymphatic system, which is only found in animals with a closed blood circulation, is an open system providing an accessory route for excess interstitial fluid to be returned to the blood.[5]
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.[27]
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, with there being no distinction between blood and interstitial fluid; this combined fluid is called hemolymph or haemolymph.[28] 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).
There are free-floating cells, the hemocytes, within the hemolymph. They play a role in the arthropod immune system.
Flatworms, such as this Pseudoceros bifurcus, lack specialized circulatory organs.
Closed circulatory system
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) always keep their circulating blood enclosed within heart chambers or blood vessels and are classified as closed, just as in humans. Still, the systems of fish, amphibians, reptiles, and birds show various stages of the evolution of the circulatory system.[29] Closed systems permit blood to be directed to the organs that require it.
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.
Mammals, birds 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.[30] Double circulatory systems permit blood to be repressurized after returning from the lungs, speeding up delivery of oxygen to tissues.
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.
History
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.[31] He also seems to have possessed knowledge of the arteries, described as 'channels' by Dwivedi & Dwivedi (2007).[31] The first major ancient Greek research into the circulatory system was completed by Plato in theTimaeus, who argues that blood circulates around the body in accordance with the general rules that govern the motions of the elements in the body; accordingly, he does not place much importance in the heart itself.[32] The valves of the heart were discovered by a physician of the Hippocrat ic school around the early 3rd century BC.[33] 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 the 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 enters between veins and arteries by very small vessels. Thus he apparently postulated capillaries but with reversed flow of blood.[citation needed]
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.[34][verification needed] 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."[35]
In 1242, the Arabian physician, Ibn al-Nafis described the process of pulmonary circulation in greater, more accurate detail than his predecessors, though he believed, as they did, in the notion of vital spirit (pneuma), which he believed was formed in the left ventricle. 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.[36] 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"[37][38] (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.
A better known discovery of pulmonary circulation was by Vesalius's successor at Padua, Realdo Colombo, in 1559.
Finally, the English physician 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 his 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."[39] 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.
An artery is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in the pulmonary circulation that carry blood to the lungs for oxygenation, and the umbilical arteries in the fetal circulation that carry deoxygenated blood to the placenta. It consists of a multi-layered artery wall wrapped into a tube-shaped channel.
The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels. Heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrients to the tissue, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest, called the mediastinum.
Blood vessels are the structures of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from the tissues. Blood vessels are typically needed to sustain life, because all of the body's tissues rely on their functionality.
Veins are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal circulations which carry oxygenated blood to the heart. In the systemic circulation, arteries carry oxygenated blood away from the heart, and veins return deoxygenated blood to the heart, in the deep veins.
Cardiopulmonary bypass (CPB) or heart-lung machine also called the pump or CPB pump is a machine that temporarily takes over the function of the heart and lungs during open-heart surgery by maintaining the circulation of blood and oxygen throughout the body. As such it is an extracorporeal device.
An air embolism, also known as a gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion injury, decompression, and a few other causes. In flora, air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress.
A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the main pulmonary artery or pulmonary trunk from the heart, and the smallest ones are the arterioles, which lead to the capillaries that surround the pulmonary alveoli.
The pulmonary circulation is a division of the circulatory system in all vertebrates. The circuit begins with deoxygenated blood returned from the body to the right atrium of the heart where it is pumped out from the right ventricle to the lungs. In the lungs the blood is oxygenated and returned to the left atrium to complete the circuit.
dextro-Transposition of the great arteries is a potentially life-threatening birth defect in the large arteries of the heart. The primary arteries are transposed.
The Fontan procedure or Fontan–Kreutzer procedure is a palliative surgical procedure used in children with univentricular hearts. It involves diverting the venous blood from the inferior vena cava (IVC) and superior vena cava (SVC) to the pulmonary arteries. The procedure varies for differing congenital heart pathologies. For example, in tricuspid atresia, the procedure can be done where the blood does not pass through the morphologic right ventricle; i.e., the systemic and pulmonary circulations are placed in series with the functional single ventricle. By contrast, in hypoplastic left heart syndrome, the heart is more reliant on the more functional right ventricle to provide blood flow to the systemic circulation. The procedure was initially performed in 1968 by Francis Fontan and Eugene Baudet from Bordeaux, France, published in 1971, simultaneously described in July 1971 by Guillermo Kreutzer from Buenos Aires, Argentina, presented at the Argentinean National Cardilogy meeting of that year and finally published in 1973.
Cardiac catheterization is the insertion of a catheter into a chamber or vessel of the heart. This is done both for diagnostic and interventional purposes.
The atrium is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves.
Transposition of the great vessels (TGV) is a group of congenital heart defects involving an abnormal spatial arrangement of any of the great vessels: superior and/or inferior venae cavae, pulmonary artery, pulmonary veins, and aorta. Congenital heart diseases involving only the primary arteries belong to a sub-group called transposition of the great arteries (TGA), which is considered the most common congenital heart lesion that presents in neonates.
The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole. After emptying, the heart relaxes and expands to receive another influx of blood returning from the lungs and other systems of the body, before again contracting to pump blood to the lungs and those systems.
In humans, the circulatory system is different before and after birth. The fetal circulation is composed of the placenta, umbilical blood vessels encapsulated by the umbilical cord, heart and systemic blood vessels. A major difference between the fetal circulation and postnatal circulation is that the lungs are not used during the fetal stage resulting in the presence of shunts to move oxygenated blood and nutrients from the placenta to the fetal tissue. At birth, the start of breathing and the severance of the umbilical cord prompt various changes that quickly transform fetal circulation into postnatal circulation.
In cardiology, a cardiac shunt is a pattern of blood flow in the heart that deviates from the normal circuit of the circulatory system. It may be described as right-left, left-right or bidirectional, or as systemic-to-pulmonary or pulmonary-to-systemic. The direction may be controlled by left and/or right heart pressure, a biological or artificial heart valve or both. The presence of a shunt may also affect left and/or right heart pressure either beneficially or detrimentally.
The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.
The Senning procedure is an atrial switch heart operation performed to treat transposition of the great arteries. It is named after its inventor, the Swedish cardiac surgeon Åke Senning (1915–2000), also known for implanting the first permanent cardiac pacemaker in 1958.
Biofluid dynamics may be considered as the discipline of biological engineering or biomedical engineering in which the fundamental principles of fluid dynamics are used to explain the mechanisms of biological flows and their interrelationships with physiological processes, in health and in diseases/disorder. It can be considered as the conjuncture of mechanical engineering and biological engineering. It spans from cells to organs, covering diverse aspects of the functionality of systemic physiology, including cardiovascular, respiratory, reproductive, urinary, musculoskeletal and neurological systems etc. Biofluid dynamics and its simulations in computational fluid dynamics (CFD) apply to both internal as well as external flows. Internal flows such as cardiovascular blood flow and respiratory airflow, and external flows such as flying and aquatic locomotion. Biological fluid Dynamics involves the study of the motion of biological fluids. It can be either circulatory system or respiratory systems. Understanding the circulatory system is one of the major areas of research. The respiratory system is very closely linked to the circulatory system and is very complex to study and understand. The study of Biofluid Dynamics is also directed towards finding solutions to some of the human body related diseases and disorders. The usefulness of the subject can also be understood by seeing the use of Biofluid Dynamics in the areas of physiology in order to explain how living things work and about their motions, in developing an understanding of the origins and development of various diseases related to human body and diagnosing them, in finding the cure for the diseases related to cardiovascular and pulmonary systems.
The heart is a muscular organ situated in the mediastinum. It consists of four chambers, four valves, two main arteries, and the conduction system. The left and right sides of the heart have different functions: the right side receives de-oxygenated blood through the superior and inferior venae cavae and pumps blood to the lungs through the pulmonary artery, and the left side receives saturated blood from the lungs.
References
1 2 Hall, John E. (2011). Guyton and Hall textbook of medical physiology (Twelfthed.). Philadelphia, Pa. p.4. ISBN9781416045748.{{cite book}}: CS1 maint: location missing publisher (link)
1 2 Saladin, Kenneth S. (2011). Human anatomy (3rded.). New York: McGraw-Hill. p.520. ISBN9780071222075.
1 2 Saladin, Kenneth S. (2011). Human anatomy (3rded.). New York: McGraw-Hill. p.540. ISBN9780071222075.
↑ Alberts, B.; Johnson, A.; Lewis, J.; Raff, M.; Roberts, K.; Walters, P. (2002). Molecular Biology of the Cell (4thed.). New York and London: Garland Science. ISBN978-0-8153-3218-3. Archived from the original on 17 August 2006. Retrieved 30 August 2017.
↑ Standring, Susan (2016). Gray's anatomy: the anatomical basis of clinical practice (Forty-firsted.). [Philadelphia]: Elsevier Limited. p.1024. ISBN9780702052309.
↑ Bailey, Regina. "Circulatory System". biology.about.com. Archived from the original on 29 November 2016. Retrieved 23 February 2022.
↑ Simões-Costa, Marcos S.; Vasconcelos, Michelle; Sampaio, Allysson C.; Cravo, Roberta M.; Linhares, Vania L.; Hochgreb, Tatiana; Yan, Chao Y.I.; Davidson, Brad; Xavier-Neto, José (2005). "The evolutionary origin of cardiac chambers". Developmental Biology. 277 (1): 1–15. doi:10.1016/j.ydbio.2004.09.026. PMID15572135.
↑ "Crocodilian Hearts". National Center for Science Education. 24 October 2008. Archived from the original on 26 September 2015. Retrieved 3 October 2015.
↑ See Timaeus 77a–81e. For a scholarly discussion, see Douglas R. Campbell, "Irrigating Blood: Plato on the Circulatory System, the Cosmos, and Elemental Motion," Journal of the History of Philosophy 62 (4): 519-541. 2024. See also Francis Cornford, Plato's Cosmology: The Timaeus of Plato, Indianapolis: Hackett, 1997.
↑ The central text here is the Hippocratic text On The Heart, which Elizabeth Craik argues was written between 300 and 250 BC. See Craik, Elizabeth. 2015. The ‘Hippocratic’ Corpus: Content and Context. New York: Routledge.
↑ 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. PMID19332359.
↑ 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. ISBN84-235-3266-6 pp. 215–228 & 62nd illustration (XLVII)
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